Clinical trial readiness in non-ambulatory boys and men with duchenne muscular dystrophy: MDA-DMD network follow-up. Muscle & nerve 2016; 54 (4): 681-689
Outcomes sensitive to change over time in non-ambulatory boys/men with Duchenne muscular dystrophy (DMD) are not well-established.Subjects (n = 91; 16.8 4.5 years old) were assessed at baseline and 6-month intervals for 2 years. We analyzed all subjects using an intent-to-treat model and a subset of stronger subjects with Brooke Scale score 4, using repeated measures.Eight patients (12-33 years old) died during the study. Sixty-six completed 12-month follow-up, and 51 completed 24-month follow-up. Those taking corticosteroids performed better at baseline, but rates of decline were similar. Forced vital capacity percent predicted (FVC% predicted) declined significantly only after 2 years. However, Brooke and Egen Klassifikation (EK) Scale scores, elbow flexion, and grip strength declined significantly over both 1 and 2 years.Brooke and EK Scale scores, elbow flexion, and grip strength were outcomes most responsive to change. FVC% predicted was responsive to change over 2 years. Corticosteroids benefited non-ambulatory DMD subjects but did not affect decline rates of measures tested here. Muscle Nerve 54: 681-689, 2016.
View details for DOI 10.1002/mus.25089
View details for PubMedID 26930423
United Dystrophinopathy Project. LTBP4 genotype predicts age of ambulatory loss in duchenne muscular dystrophy
Precise Correction of Disease Mutations in Induced Pluripotent Stem Cells Derived From Patients With Limb Girdle Muscular Dystrophy. Molecular therapy : the journal of the American Society of Gene Therapy 2016; 24 (4): 685-696
Limb girdle muscular dystrophies types 2B (LGMD2B) and 2D (LGMD2D) are degenerative muscle diseases caused by mutations in the dysferlin and alpha-sarcoglycan genes, respectively. Using patient-derived induced pluripotent stem cells (iPSC), we corrected the dysferlin nonsense mutation c.5713C>T; p.R1905X and the most common alpha-sarcoglycan mutation, missense c.229C>T; p.R77C, by single-stranded oligonucleotide-mediated gene editing, using the CRISPR/Cas9 gene-editing system to enhance the frequency of homology-directed repair. We demonstrated seamless, allele-specific correction at efficiencies of 0.7-1.5%. As an alternative, we also carried out precise gene addition strategies for correction of the LGMD2B iPSC by integration of wild-type dysferlin cDNA into the H11 safe harbor locus on chromosome 22, using dual integrase cassette exchange (DICE) or TALEN-assisted homologous recombination for insertion precise (THRIP). These methods employed TALENs and homologous recombination, and DICE also utilized site-specific recombinases. With DICE and THRIP, we obtained targeting efficiencies after selection of ~20%. We purified iPSC corrected by all methods and verified rescue of appropriate levels of dysferlin and alpha-sarcoglycan protein expression and correct localization, as shown by immunoblot and immunocytochemistry. In summary, we demonstrate for the first time precise correction of LGMD iPSC and validation of expression, opening the possibility of cell therapy utilizing these corrected iPSC.
View details for DOI 10.1038/mt.2016.40
View details for PubMedID 26916285
Splicing misregulation of SCN5A contributes to cardiac-conduction delay and heart arrhythmia in myotonic dystrophy NATURE COMMUNICATIONS 2016; 7
Myotonic dystrophy (DM) is caused by the expression of mutant RNAs containing expanded CUG repeats that sequester muscleblind-like (MBNL) proteins, leading to alternative splicing changes. Cardiac alterations, characterized by conduction delays and arrhythmia, are the second most common cause of death in DM. Using RNA sequencing, here we identify novel splicing alterations in DM heart samples, including a switch from adult exon 6B towards fetal exon 6A in the cardiac sodium channel, SCN5A. We find that MBNL1 regulates alternative splicing of SCN5A mRNA and that the splicing variant of SCN5A produced in DM presents a reduced excitability compared with the control adult isoform. Importantly, reproducing splicing alteration of Scn5a in mice is sufficient to promote heart arrhythmia and cardiac-conduction delay, two predominant features of myotonic dystrophy. In conclusion, misregulation of the alternative splicing of SCN5A may contribute to a subset of the cardiac dysfunctions observed in myotonic dystrophy.
View details for DOI 10.1038/ncomms11067
View details for Web of Science ID 000373819100001
View details for PubMedID 27063795
Genotype-phenotype characteristics and baseline natural history of heritable neuropathies caused by mutations in the MPZ gene BRAIN 2015; 138
We aimed to characterize genotype-phenotype correlations and establish baseline clinical data for peripheral neuropathies caused by mutations in the myelin protein zero (MPZ) gene. MPZ mutations are the second leading cause of Charcot-Marie-Tooth disease type 1. Recent research makes clinical trials for patients with MPZ mutations a realistic possibility. However, the clinical severity varies with different mutations and natural history data on progression is sparse. We present cross-sectional data to begin to define the phenotypic spectrum and clinical baseline of patients with these mutations. A cohort of patients with MPZ gene mutations was identified in 13 centres of the Inherited Neuropathies Consortium - Rare Disease Clinical Research Consortium (INC-RDCRC) between 2009 and 2012 and at Wayne State University between 1996 and 2009. Patient phenotypes were quantified by the Charcot-Marie-Tooth disease neuropathy score version 1 or 2 and the Charcot-Marie-Tooth disease paediatric scale outcome instruments. Genetic testing was performed in all patients and/or in first- or second-degree relatives to document mutation in MPZ gene indicating diagnosis of Charcot-Marie-Tooth disease type 1B. There were 103 patients from 71 families with 47 different MPZ mutations with a mean age of 40 years (range 3-84 years). Patients and mutations were separated into infantile, childhood and adult-onset groups. The infantile onset group had higher Charcot-Marie-Tooth disease neuropathy score version 1 or 2 and slower nerve conductions than the other groups, and severity increased with age. Twenty-three patients had no family history of Charcot-Marie-Tooth disease. Sixty-one patients wore foot/ankle orthoses, 19 required walking assistance or support, and 10 required wheelchairs. There was hearing loss in 21 and scoliosis in 17. Forty-two patients did not begin walking until after 15 months of age. Half of the infantile onset patients then required ambulation aids or wheelchairs for ambulation. Our results demonstrate that virtually all MPZ mutations are associated with specific phenotypes. Early onset (infantile and childhood) phenotypes likely represent developmentally impaired myelination, whereas the adult-onset phenotype reflects axonal degeneration without antecedent demyelination. Data from this cohort of patients will provide the baseline data necessary for clinical trials of patients with Charcot-Marie-Tooth disease caused by MPZ gene mutations.
View details for DOI 10.1093/brain/awv241
View details for Web of Science ID 000365135700016
View details for PubMedID 26310628
MBNL Sequestration by Toxic RNAs and RNA Misprocessing in the Myotonic Dystrophy Brain CELL REPORTS 2015; 12 (7): 1159-1168
CMT subtypes and disease burden in patients enrolled in the Inherited Neuropathies Consortium natural history study: a cross-sectional analysis JOURNAL OF NEUROLOGY NEUROSURGERY AND PSYCHIATRY 2015; 86 (8): 873-878
The international Inherited Neuropathy Consortium (INC) was created with the goal of obtaining much needed natural history data for patients with Charcot-Marie-Tooth (CMT) disease. We analysed clinical and genetic data from patients in the INC to determine the distribution of CMT subtypes and the clinical impairment associated with them.We analysed data from 1652 patients evaluated at 13 INC centres. The distribution of CMT subtypes and pathogenic genetic mutations were determined. The disease burden of all the mutations was assessed by the CMT Neuropathy Score (CMTNS) and CMT Examination Score (CMTES).997 of the 1652 patients (60.4%) received a genetic diagnosis. The most common CMT subtypes were CMT1A/PMP22 duplication, CMT1X/GJB1 mutation, CMT2A/MFN2 mutation, CMT1B/MPZ mutation, and hereditary neuropathy with liability to pressure palsy/PMP22 deletion. These five subtypes of CMT accounted for 89.2% of all genetically confirmed mutations. Mean CMTNS for some but not all subtypes were similar to those previously reported.Our findings confirm that large numbers of patients with a representative variety of CMT subtypes have been enrolled and that the frequency of achieving a molecular diagnosis and distribution of the CMT subtypes reflects those previously reported. Measures of severity are similar, though not identical, to results from smaller series. This study confirms that it is possible to assess patients in a uniform way between international centres, which is critical for the planned natural history study and future clinical trials. These data will provide a representative baseline for longitudinal studies of CMT.ID number NCT01193075.
View details for DOI 10.1136/jnnp-2014-308826
View details for Web of Science ID 000357884300009
View details for PubMedID 25430934
OUTCOME RELIABILITY IN NON-AMBULATORY BOYS/MEN WITH DUCHENNE MUSCULAR DYSTROPHY MUSCLE & NERVE 2015; 51 (4): 522-532
Background: Therapeutic trials in Duchenne muscular dystrophy (DMD) often exclude non-ambulatory individuals. Here we establish optimal and reliable assessments in a multicenter trial. Methods: Non-ambulatory boys/men with DMD (n=91;16.7 4.5 years) were assessed by trained clinical evaluators. Feasibility (percentage completing task) and reliability [intra-class correlation coefficients (ICCs) between AM and PM tests] were measured. Results: Forced Vital Capacity (FVC, 100% of subjects) showed a mean 47.8 22% predicted (ICC 0.98). Brooke upper extremity functional rating (Brooke) and Egen Klassifikation (EK) scales in 100% of subjects showed ICCs from 0.93-0.99. Manual muscle testing, range of motion, nine-hole peg, and Jebsen-Taylor Hand function testing (JHFT) had variable feasibility (99% to 70%) with ICC also ranging from 0.99 to 0.64. We found beneficial effects of different forms of corticosteroids for Brooke Scale, %predicted FVC, and hand and finger strength. Conclusion: Reliable assessment of non-ambulatory boys/men with DMD is possible. Clinical trials will have to consider corticosteroid use. 2014 Wiley Periodicals, Inc.
View details for DOI 10.1002/mus.24346
View details for Web of Science ID 000351679400009
View details for PubMedID 25056178
Clinical Phenotypes as Predictors of the Outcome of Skipping around DMD Exon 45 ANNALS OF NEUROLOGY 2015; 77 (4): 668-674
Exon-skipping therapies aim to convert Duchenne muscular dystrophy (DMD) into less severe Becker muscular dystrophy (BMD) by altering pre-mRNA splicing to restore an open reading frame, allowing translation of an internally deleted and partially functional dystrophin protein. The most common single exon deletion-exon 45 (45)-may theoretically be treated by skipping of either flanking exon (44 or 46). We sought to predict the impact of these by assessing the clinical severity in dystrophinopathy patients.Phenotypic data including clinical diagnosis, age at wheelchair use, age at loss of ambulation, and presence of cardiomyopathy were analyzed from 41 dystrophinopathy patients containing equivalent in-frame deletions.As expected, deletions of either exons 45 to 47 (45-47) or exons 45 to 48 (45-48) result in BMD in 97% (36 of 37) of subjects. Unexpectedly, deletion of exons 45 to 46 (45-46) is associated with the more severe DMD phenotype in 4 of 4 subjects despite an in-frame transcript. Notably, no patients with a deletion of exons 44 to 45 (44-45) were found within the United Dystrophinopathy Project database, and this mutation has only been reported twice before, which suggests an ascertainment bias attributable to a very mild phenotype.The observation that 45-46 patients have typical DMD suggests that the conformation of the resultant protein may result in protein instability or altered binding of critical partners. We conclude that in DMD patients with 45, skipping of exon 44 and multiexon skipping of exons 46 and 47 (or exons 46-48) are better potential therapies than skipping of exon 46 alone.
View details for DOI 10.1002/ana.24365
View details for Web of Science ID 000352102500011
View details for PubMedID 25612243
ATALUREN TREATMENT OF PATIENTS WITH NONSENSE MUTATION DYSTROPHINOPATHY MUSCLE & NERVE 2014; 50 (4): 477-487
Dystrophinopathy is a rare, severe muscle disorder, and nonsense mutations are found in 13% of cases. Ataluren was developed to enable ribosomal readthrough of premature stop codons in nonsense mutation (nm) genetic disorders.Randomized, double-blind, placebo-controlled study; males 5 years with nm-dystrophinopathy received study drug orally 3 times daily, ataluren 10, 10, 20 mg/kg (N=57); ataluren 20, 20, 40 mg/kg (N=60); or placebo (N=57) for 48 weeks. The primary endpoint was change in 6-Minute Walk Distance (6MWD) at Week 48.Ataluren was generally well tolerated. The primary endpoint favored ataluren 10, 10, 20 mg/kg versus placebo; the week 48 6MWD =31.3 meters, post hoc P=0.056. Secondary endpoints (timed function tests) showed meaningful differences between ataluren 10, 10, 20 mg/kg, and placebo.As the first investigational new drug targeting the underlying cause of nm-dystrophinopathy, ataluren offers promise as a treatment for this orphan genetic disorder with high unmet medical need. Muscle Nerve 50: 477-487, 2014.
View details for DOI 10.1002/mus.24332
View details for Web of Science ID 000342634100002
View details for PubMedID 25042182
Congenital muscular dystrophy and generalized epilepsy caused by GMPPB mutations BRAIN RESEARCH 2014; 1575: 66-71
The alpha-dystroglycanopathies are genetically heterogeneous muscular dystrophies that result from hypoglycosylation of alpha-dystroglycan (-DG). Alpha-dystroglycan is an essential link between the extracellular matrix and the muscle fiber sarcolemma, and proper glycosylation is critical for its ability to bind to ligands in the extracellular matrix. We sought to identify the genetic basis of alpha-dystroglycanopathy in a family wherein the affected individuals presented with congenital muscular dystrophy, brain abnormalities and generalized epilepsy. We performed whole exome sequencing and identified compound heterozygous GMPPB mutations in the affected children. GMPPB is an enzyme in the glycosylation pathway, and GMPPB mutations were recently linked to eight cases of alpha-dystroglycanopathy with a range of symptoms. We identified a novel mutation in GMPPB (p.I219T) as well as a previously published mutation (p.R287Q). Thus, our work further confirms a role for GMPPB defects in alpha-dystroglycanopathy, and suggests that glycosylation may play a role in the neuronal membrane channels or networks involved in the physiology of generalized epilepsy syndromes. This article is part of a Special Issue entitled RNA Metabolism 2013.
View details for DOI 10.1016/j.brainres.2014.04.028
View details for Web of Science ID 000340322800007
Tractography reveals diffuse white matter abnormalities in Myotonic Dystrophy Type 1 JOURNAL OF THE NEUROLOGICAL SCIENCES 2014; 341 (1-2): 73-78
Cerebral involvement in Myotonic Dystrophy Type 1 (DM1) is well-established but not well characterized. This study applied new Diffusion Tensor Imaging (DTI) tractography to characterize white matter disturbance in adults with DM1. Forty-five participants with DM1 and 44 control participants had MRIs on a Siemens 3T TIM Trio scanner. Data were processed with TRActs Constrained by UnderLying Anatomy (TRACULA) and 7 tracts were evaluated. Bilateral disturbances in white matter integrity were seen in all tracts in participants with DM1 compared to controls. There were no right-left hemisphere differences. The resulting DTI metrics were correlated with cognitive functioning, particularly working memory and processing speed. Motor speed was not significantly correlated with white matter microstructural integrity and, thus, was not the core explanation for the working memory and processing speed findings. White matter integrity was correlated with important clinical variables including the muscular impairment rating scale (MIRS). CTG repeat length was moderately associated with white matter status in corticospinal tract and cingulum. Sleepiness (Epworth Sleepiness Scale) was moderately associated with white matter status in the superior longitudinal fasciculus and cingulum. Overall, the results add to an emerging literature showing widespread white matter disturbances in both early-onset and adult-onset DM1. Results suggest that further investigation of white matter pathology is warranted in DM1 and that non-invasive measures such as DTI have a potentially important clinical value in characterizing the status of individuals with DM1.
View details for DOI 10.1016/j.jns.2014.04.005
View details for Web of Science ID 000337262200016
View details for PubMedID 24768314
One Year Outcome of Boys With Duchenne Muscular Dystrophy Using the Bayley-III Scales of Infant and Toddler Development PEDIATRIC NEUROLOGY 2014; 50 (6): 557-563
The pathogenesis of Duchenne muscular dystrophy starts before birth. Despite this, clinical trials exclude young boys because traditional outcome measures rely on cooperation. We recently used the Bayley-III Scales of Infant and Toddler Development to study 24 infants and boys with Duchenne muscular dystrophy. Clinical evaluators at six centers were trained and certified to perform the Bayley-III. Here, we report 6- and 12-month follow-up of two subsets of these boys.Nineteen boys (1.9 0.8 years) were assessed at baseline and 6 months. Twelve boys (1.5 0.8 years) were assessed at baseline, 6, and 12 months.Gross motor scores were lower at baseline compared with published controls (6.2 1.7; normal 10 3; P < 0.0001) and revealed a further declining trend to 5.7 1.7 (P = 0.20) at 6 months. Repeated measures analysis of the 12 boys monitored for 12 months revealed that gross motor scores, again low at baseline (6.6 1.7; P < 0.0001), declined at 6 months (5.9 1.8) and further at 12 months (5.3 2.0) (P = 0.11). Cognitive and language scores were lower at baseline compared with normal children (range, P = 0.002-<0.0001) and did not change significantly at 6 or 12 months (range, P = 0.89-0.09). Fine motor skills, also low at baseline, improved >1 year (P = 0.05).Development can reliably be measured in infants and young boys with Duchenne muscular dystrophy across time using the Bayley-III. Power calculations using these data reveal that motor development may be used as an outcome measure.
View details for DOI 10.1016/j.pediatrneurol.2014.02.006
View details for Web of Science ID 000336643700004
View details for PubMedID 24842254
Exome sequencing identifies a DNAJB6 mutation in a family with dominantly-inherited limb-girdle muscular dystrophy NEUROMUSCULAR DISORDERS 2014; 24 (5): 431-435
Limb-girdle muscular dystrophy primarily affects the muscles of the hips and shoulders (the "limb-girdle" muscles), although it is a heterogeneous disorder that can present with varying symptoms. There is currently no cure. We sought to identify the genetic basis of limb-girdle muscular dystrophy type 1 in an American family of Northern European descent using exome sequencing. Exome sequencing was performed on DNA samples from two affected siblings and one unaffected sibling and resulted in the identification of eleven candidate mutations that co-segregated with the disease. Notably, this list included a previously reported mutation in DNAJB6, p.Phe89Ile, which was recently identified as a cause of limb-girdle muscular dystrophy type 1D. Additional family members were Sanger sequenced and the mutation in DNAJB6 was only found in affected individuals. Subsequent haplotype analysis indicated that this DNAJB6 p.Phe89Ile mutation likely arose independently of the previously reported mutation. Since other published mutations are located close by in the G/F domain of DNAJB6, this suggests that the area may represent a mutational hotspot. Exome sequencing provided an unbiased and effective method for identifying the genetic etiology of limb-girdle muscular dystrophy type 1 in a previously genetically uncharacterized family. This work further confirms the causative role of DNAJB6 mutations in limb-girdle muscular dystrophy type 1D.
View details for DOI 10.1016/j.nmd.2014.01.014
View details for Web of Science ID 000336349400011
Diagnostic odyssey of patients with myotonic dystrophy JOURNAL OF NEUROLOGY 2013; 260 (10): 2497-2504
The onset and symptoms of the myotonic dystrophies are diverse, complicating their diagnoses and limiting a comprehensive approach to their clinical care. This report analyzes the diagnostic delay (time from onset of first symptom to diagnosis) in a large sample of myotonic dystrophy (DM) patients enrolled in the US National Registry [679 DM type 1 (DM1) and 135 DM type 2 (DM2) patients]. Age of onset averaged 34.014.1years in DM2 patients compared to 26.113.2years in DM1 (p<0.0001). The most common initial symptom in DM2 patients was leg weakness (32.6%) compared to grip myotonia in DM1 (38.3%). Pain was reported as the first symptom in 11.1% of DM2 and 3.0% of DM1 patients (p<0.0001). Reaching the correct diagnosis in DM2 took 14years on average (double the time compared to DM1) and a significantly higher percentage of patients underwent extended workup including electromyography, muscle biopsies, and finally genetic testing. DM patients who were index cases experienced similar diagnostic delays to non-index cases of DM. Further evaluation of how to shorten these diagnostic delays and limit their impact on burdens of disease, family planning, and symptom management is needed.
View details for DOI 10.1007/s00415-013-6993-0
View details for Web of Science ID 000325639400006
View details for PubMedID 23807151
Role of telomere dysfunction in cardiac failure in Duchenne muscular dystrophy. Nature cell biology 2013; 15 (8): 895-904
Duchenne muscular dystrophy (DMD), the most common inherited muscular dystrophy of childhood, leads to death due to cardiorespiratory failure. Paradoxically, mdx mice with the same genetic deficiency of dystrophin exhibit minimal cardiac dysfunction, impeding the development of therapies. We postulated that the difference between mdx and DMD might result from differences in telomere lengths in mice and humans. We show here that, like DMD patients, mice that lack dystrophin and have shortened telomeres (mdx/mTR(KO)) develop severe functional cardiac deficits including ventricular dilation, contractile and conductance dysfunction, and accelerated mortality. These cardiac defects are accompanied by telomere erosion, mitochondrial fragmentation and increased oxidative stress. Treatment with antioxidants significantly retards the onset of cardiac dysfunction and death of mdx/mTR(KO) mice. In corroboration, all four of the DMD patients analysed had 45% shorter telomeres in their cardiomyocytes relative to age- and sex-matched controls. We propose that the demands of contraction in the absence of dystrophin coupled with increased oxidative stress conspire to accelerate telomere erosion culminating in cardiac failure and death. These findings provide strong support for a link between telomere length and dystrophin deficiency in the etiology of dilated cardiomyopathy in DMD and suggest preventive interventions.
View details for DOI 10.1038/ncb2790
View details for PubMedID 23831727
Role of telomere dysfunction in cardiac failure in Duchenne muscular dystrophy NATURE CELL BIOLOGY 2013; 15 (8): 895-U300
Motor and cognitive assessment of infants and young boys with Duchenne Muscular Dystrophy: results from the Muscular Dystrophy Association DMD Clinical Research Network NEUROMUSCULAR DISORDERS 2013; 23 (7): 529-539
Therapeutic trials in Duchenne Muscular Dystrophy (DMD) exclude young boys because traditional outcome measures rely on cooperation. The Bayley III Scales of Infant and Toddler Development (Bayley III) have been validated in developing children and those with developmental disorders but have not been studied in DMD. Expanded Hammersmith Functional Motor Scale (HFMSE) and North Star Ambulatory Assessment (NSAA) may also be useful in this young DMD population. Clinical evaluators from the MDA-DMD Clinical Research Network were trained in these assessment tools. Infants and boys with DMD (n=24; 1.90.7years) were assessed. The mean Bayley III motor composite score was low (82.88; p.0001) (normal=10015). Mean gross motor and fine motor function scaled scores were low (both p.0001). The mean cognitive comprehensive (p=.0002), receptive language (p.0001), and expressive language (p=.0001) were also low compared to normal children. Age was negatively associated with Bayley III gross motor (r=-0.44; p=.02) but not with fine motor, cognitive, or language scores. HFMSE (n=23) showed a mean score of 3113. NSAA (n=18 boys; 2.20.4years) showed a mean score of 125. Outcome assessments of young boys with DMD are feasible and in this multicenter study were best demonstrated using the Bayley III.
View details for DOI 10.1016/j.nmd.2013.04.005
View details for Web of Science ID 000321997800002
View details for PubMedID 23726376
LTBP4 genotype predicts age of ambulatory loss in duchenne muscular dystrophy ANNALS OF NEUROLOGY 2013; 73 (4): 481-488
OBJECTIVE: Duchenne muscular dystrophy (DMD) displays a clinical range that is not fully explained by the primary DMD mutations. Ltbp4, encoding latent transforming growth factor- binding protein 4, was previously discovered in a genome-wide scan as a modifier of murine muscular dystrophy. We sought to determine whether LTBP4 genotype influenced DMD severity in a large patient cohort. METHODS: We analyzed nonsynonymous single nucleotide polymorphisms (SNPs) from human LTBP4 in 254 nonambulatory subjects with known DMD mutations. These SNPs, V194I, T787A, T820A, and T1140M, form the VTTT and IAAM LTBP4 haplotypes. RESULTS: Individuals homozygous for the IAAM LTBP4 haplotype remained ambulatory significantly longer than those heterozygous or homozygous for the VTTT haplotype. Glucocorticoid-treated patients who were IAAM homozygotes lost ambulation at 12.5 3.3 years compared to 10.7 2.1 years for treated VTTT heterozygotes or homozygotes. IAAM fibroblasts exposed to transforming growth factor (TGF) displayed reduced phospho-SMAD signaling compared to VTTT fibroblasts, consistent with LTBP4' role as a regulator of TGF. INTERPRETATION: LTBP4 haplotype influences age at loss of ambulation, and should be considered in the management of DMD patients. ANN NEUROL 2013.
View details for DOI 10.1002/ana.23819
View details for Web of Science ID 000319523800009
View details for PubMedID 23440719
Diffusion tensor imaging reveals widespread white matter abnormalities in children and adolescents with myotonic dystrophy type 1 JOURNAL OF NEUROLOGY 2013; 260 (4): 1122-1131
Diffusion tensor imaging was used to evaluate cerebral white matter in 16 patients (ages 9-18) with myotonic dystrophy type 1 compared to 15 matched controls. Patients with myotonic dystrophy showed abnormalities in mean diffusivity compared to controls in frontal, temporal, parietal, and occipital white matter and in all individual tracts examined. Whole cerebrum mean diffusivity was 8.6 % higher overall in patients with myotonic dystrophy compared to controls. Whole cerebrum fractional anisotropy was also abnormal (10.8 % low overall) in all regions and tracts except corticospinal tracts. Follow-up analysis of parallel and perpendicular diffusivity suggests possible relative preservation of myelin in corticospinal tracts. Correlations between Wechsler working memory performance and mean diffusivity were strong for all regions. Frontal and temporal fractional anisotropy were correlated with working memory as well. Results are consistent with earlier studies demonstrating that significant white matter disturbances are characteristic in young patients with myotonic dystrophy and that these abnormalities are associated with the degree of working memory impairment seen in this disease.
View details for DOI 10.1007/s00415-012-6771-4
View details for Web of Science ID 000317351900022
View details for PubMedID 23192171
A focal domain of extreme demethylation within D4Z4 in FSHD2 NEUROLOGY 2013; 80 (4): 392-399
Facioscapulohumeral muscular dystrophy (FSHD) is a neuromuscular disease with an unclear genetic mechanism. Most patients have a contraction of the D4Z4 macrosatellite repeat array at 4qter, which is thought to cause partial demethylation (FSHD1) of the contracted allele. Demethylation has been surveyed at 3 restriction enzyme sites in the first repeat and only a single site across the entire array, and current models postulate that a generalized D4Z4 chromatin alteration causes FSHD. The background of normal alleles has confounded the study of epigenetic alterations; however, rare patients (FSHD2) have a form of the disease in which demethylation is global, i.e., on all D4Z4 elements throughout the genome. Our objective was to take advantage of the global nature of FSHD2 to identify where disease-relevant methylation changes occur within D4Z4.Using bisulfite sequencing of DNA from blood and myoblast cells, methylation levels at 74 CpG sites across 3 disparate regions within D4Z4 were measured in FSHD2 patients and controls.We found that rates of demethylation caused by FSHD2 are not consistent across D4Z4. We identified a focal region of extreme demethylation within a 5' domain, which we named DR1. Other D4Z4 regions, including the DUX4 ORF, were hypomethylated but to a much lesser extent.These data challenge the simple view that FSHD is caused by a broad "opening" of D4Z4 and lead us to postulate that the region of focal demethylation is the site of action of the key D4Z4 chromatin regulatory factors that go awry in FSHD.
View details for Web of Science ID 000313961000018
View details for PubMedID 23284062
A randomized, double-blind trial of lisinopril and losartan for the treatment of cardiomyopathy in duchenne muscular dystrophy. PLoS currents 2013; 5
This study sought to compare the effectiveness and safety of an angiotensin converting enzyme inhibitor (ACE-I) (lisinopril) vs. an angiotensin receptor blocker (ARB) (losartan) for the treatment of cardiomyopathy (CM) in boys with Duchenne muscular dystrophy (DMD).Development of CM is universal in boys with DMD. ACE-I and ARB have both been suggested as effective treatment options. ARBs have been associated with skeletal muscle regeneration in a mouse model of DMD. The question of which, if either, is more effective for CM treatment in DMD remains. The purpose of this multicenter double-blind prospective study was to compare efficacy and safety of lisinopril versus losartan in the treatment of newly diagnosed CM in boys with DMD.Echocardiographic technician inter- and intraobserver variability were tested on 2 separate days on 2 different boys with DMD CM. Results were compared with paired t-testing. Twenty-two boys with newly diagnosed DMD CM (echocardiographic ejection fraction (EF) 10% EF drop. Three boys in the aCE-I group had 3 visits, due to study funding termination. Two were withdrawn because of low EF. All their data are included in the analysis for as long as they remained in the study. Mean EF's were similar at baseline (47.5%- ACE-I, 48.4%- ARB). After 1 year each group significantly improved to 54.6% and 55.2% respectively (p=.02). There was no difference between the 2 treatment groups at 1 year.Inter-observer and intra-observer reliability studies showed no differences between echocardiographers on serial examinations. EF improved equally in the two groups. There is no therapeutic difference in EF improvement between lisinopril and losartan over the one-year duration for treatment of boys with DMD-related CM.ClinicalTrials.gov NCT01982695.
View details for DOI 10.1371/currents.md.2cc69a1dae4be7dfe2bcb420024ea865
View details for PubMedID 24459612
Cerebral and muscle MRI abnormalities in myotonic dystrophy NEUROMUSCULAR DISORDERS 2012; 22 (6): 483-491
Pathophysiological mechanisms underlying the clinically devastating CNS features of myotonic dystrophy (DM) remain more enigmatic and controversial than do the muscle abnormalities of this common form of muscular dystrophy. To better define CNS and cranial muscle changes in DM, we used quantitative volumetric and diffusion tensor MRI methods to measure cerebral and masticatory muscle differences between controls (n=5) and adults with either congenital (n=5) or adult onset (n=5) myotonic dystrophy type 1 and myotonic dystrophy type 2 (n=5). Muscle volumes were diminished in DM1 and strongly correlated with reduced white matter integrity and gray matter volume. Moreover, correlation of reduced fractional anisotropy (white matter integrity) and gray matter volume in both DM1 and DM2 suggests that these abnormalities may share a common underlying pathophysiological mechanism. Further quantitative temporal and spatial characterization of these features will help delineate developmental and progressive neurological components of DM, and help determine the causative molecular and cellular mechanisms.
View details for DOI 10.1016/j.nmd.2012.01.003
View details for Web of Science ID 000305164900002
View details for PubMedID 22290140
Clinical and genetic features of spinocerebellar ataxia type 8. Handbook of clinical neurology 2012; 103: 493-505
Spinocerebellar ataxia type 5. Handbook of clinical neurology 2012; 103: 451-459
In 1994, Ranum and colleagues identified a ten-generation American kindred with a relatively mild autosomal dominant form of spinocerebellar ataxia (Ranum et al., 1994). The mutation was mapped to the centromeric region of chromosome 11, and the disorder designated SCA5 (Ranum et al., 1994). Using a multifaceted mapping approach, Ikeda et al. (2006) discovered that ?-III spectrin (SPTBN2) mutations cause spinocerebellar ataxia type 5 (SCA5) in the American kindred and two additional independently reported SCA5 families. The American and French families have separate in-frame deletions of 39 and 15 bp, respectively, in the third of 17 spectrin repeat motifs. A third mutation, found in a German family, is located in the second calponin homology domain, a region known to bind actin and Arp1. Consistent with Purkinje cell degeneration in SCA5, ?-III spectrin is highly expressed in cerebellar Purkinje cells. TIRF microscopy performed on cell lines transiently transfected with mutant or wild-type spectrin shows that mutant ?-III spectrin fails to stabilize the glutamate transporter EAAT4 at the plasma membrane. Additionally, marked differences in EAAT4 and GluR?2 were found by protein blot and cell fractionation in SCA5 autopsy tissue. This review summarizes data showing that ?-III spectrin mutations are a novel cause of neurodegenerative disease, which may affect the stabilization or trafficking of membrane proteins.
View details for DOI 10.1016/B978-0-444-51892-7.00028-0
View details for PubMedID 21827906
2010 Marigold therapeutic strategies for myotonic dystrophy. ELSEVIER B.V. 2012: 87-94
Randomized, blinded trial of weekend vs daily prednisone in Duchenne muscular dystrophy NEUROLOGY 2011; 77 (5): 444-452
To perform a double-blind, randomized study comparing efficacy and safety of daily and weekend prednisone in boys with Duchenne muscular dystrophy (DMD).A total of 64 boys with DMD who were between 4 and 10 years of age were randomized at 1 of 12 centers of the Cooperative International Neuromuscular Research Group. Efficacy and safety of 2 prednisone schedules (daily 0.75 mg/kg/day and weekend 10 mg/kg/wk) were evaluated over 12 months.Equivalence was met for weekend and daily dosing of prednisone for the primary outcomes of quantitative muscle testing (QMT) arm score and QMT leg score. Secondary strength scores for QMT elbow flexors also showed equivalence between the 2 treatment groups. Overall side effect profiles of height and weight, bone density, cataract formation, blood pressure, and behavior, analyzed at 12 months, did not differ between weekend and daily dosing of prednisone.Weekend dosing of prednisone is equally beneficial to the standard daily dosing of prednisone. Analysis of side effect profiles demonstrated overall tolerability of both dosing regimens.This study provides Class I evidence that weekend prednisone dosing is as safe and effective as daily prednisone in preserving muscle strength and preventing body mass index increases in boys with DMD over a 12-month period.
View details for DOI 10.1212/WNL.0b013e318227b164
View details for Web of Science ID 000293383100012
View details for PubMedID 21753160
Misregulation of miR-1 processing is associated with heart defects in myotonic dystrophy NATURE STRUCTURAL & MOLECULAR BIOLOGY 2011; 18 (7): 840-U120
Myotonic dystrophy is an RNA gain-of-function disease caused by expanded CUG or CCUG repeats, which sequester the RNA binding protein MBNL1. Here we describe a newly discovered function for MBNL1 as a regulator of pre-miR-1 biogenesis and find that miR-1 processing is altered in heart samples from people with myotonic dystrophy. MBNL1 binds to a UGC motif located within the loop of pre-miR-1 and competes for the binding of LIN28, which promotes pre-miR-1 uridylation by ZCCHC11 (TUT4) and blocks Dicer processing. As a consequence of miR-1 loss, expression of GJA1 (connexin 43) and CACNA1C (Cav1.2), which are targets of miR-1, is increased in both DM1- and DM2-affected hearts. CACNA1C and GJA1 encode the main calcium- and gap-junction channels in heart, respectively, and we propose that their misregulation may contribute to the cardiac dysfunctions observed in affected persons.
View details for DOI 10.1038/nsmb.2067
View details for Web of Science ID 000292507500013
View details for PubMedID 21685920
Nonsense Mutation-Associated Becker Muscular Dystrophy: Interplay Between Exon Definition and Splicing Regulatory Elements within the DMD Gene HUMAN MUTATION 2011; 32 (3): 299-308
Nonsense mutations are usually predicted to function as null alleles due to premature termination of protein translation. However, nonsense mutations in the DMD gene, encoding the dystrophin protein, have been associated with both the severe Duchenne Muscular Dystrophy (DMD) and milder Becker Muscular Dystrophy (BMD) phenotypes. In a large survey, we identified 243 unique nonsense mutations in the DMD gene, and for 210 of these we could establish definitive phenotypes. We analyzed the reading frame predicted by exons flanking those in which nonsense mutations were found, and present evidence that nonsense mutations resulting in BMD likely do so by inducing exon skipping, confirming that exonic point mutations affecting exon definition have played a significant role in determining phenotype. We present a new model based on the combination of exon definition and intronic splicing regulatory elements for the selective association of BMD nonsense mutations with a subset of DMD exons prone to mutation-induced exon skipping.
View details for DOI 10.1002/humu.21426
View details for Web of Science ID 000288034100007
View details for PubMedID 21972111
White matter abnormalities and neurocognitive correlates in children and adolescents with myotonic dystrophy type 1: A diffusion tensor imaging study NEUROMUSCULAR DISORDERS 2011; 21 (2): 89-96
Diffusion tensor imaging was used to evaluate cerebral white matter in eight patients (ages 10-17), with myotonic dystrophy type 1 (3 congenital-onset, 5 juvenile-onset) compared to eight controls matched for age and sex. Four regions of interest were examined: inferior frontal, superior frontal, supracallosal, and occipital. The myotonic dystrophy group showed white matter abnormalities compared to controls in all regions. All indices of white matter integrity were abnormal: fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. With no evidence of regional variation, correlations between whole cerebrum white matter fractional anisotropy and neurocognitive functioning were examined in the patients. Strong correlations were observed between whole cerebrum fractional anisotropy and full-scale intelligence and a measure of executive functioning. Results indicate that significant white matter abnormality is characteristic of young patients with myotonic dystrophy type 1 and that the white matter abnormality seen with neuroimaging has implications for cognitive functioning.
View details for DOI 10.1016/j.nmd.2010.11.013
View details for Web of Science ID 000290245200002
View details for PubMedID 21169018
TRAUMA, TDP-43, AND AMYOTROPHIC LATERAL SCLEROSIS MUSCLE & NERVE 2010; 42 (6): 851-852
Targeting parents for the treatment of pediatric obesity in boys with Duchenne muscular dystrophy: A case series EATING AND WEIGHT DISORDERS-STUDIES ON ANOREXIA BULIMIA AND OBESITY 2010; 15 (3): E161-E165
Obesity is a major public health concern in children. Obesity occurs frequently in boys with Duchenne muscular dystrophy (DMD), complicating treatment and impairing functioning. Parent-focused interventions to facilitate weight loss have been successful in other pediatric samples but have not been studied with this population. The current investigation examined the feasibility and potential efficacy of parent-focused treatment to improve healthy eating and physical activity of parents and eating and weight in their sons with DMD. Three families participated in this case series. Resulting changes in body weight among boys with DMD were an outcome variable. Findings indicate inconsistent changes in boys' weight, decreases in parent weight, increases in healthy foods available in the home, and increases in children's perceived quality of life. Participant ratings of treatment suitability and satisfaction were generally favorable. These preliminary findings support the use of parent-focused psychoeducation for the treatment of obesity in children with DMD.
View details for Web of Science ID 000286027100006
View details for PubMedID 21150251
Mutational Spectrum of DMD Mutations in Dystrophinopathy Patients: Application of Modern Diagnostic Techniques to a Large Cohort HUMAN MUTATION 2009; 30 (12): 1657-1666
Mutations in the DMD gene, encoding the dystrophin protein, are responsible for the dystrophinopathies Duchenne Muscular Dystrophy (DMD), Becker Muscular Dystrophy (BMD), and X-linked Dilated Cardiomyopathy (XLDC). Mutation analysis has traditionally been challenging, due to the large gene size (79 exons over 2.2 Mb of genomic DNA). We report a very large aggregate data set comprised of DMD mutations detected in samples from patients enrolled in the United Dystrophinopathy Project, a multicenter research consortium, and in referral samples submitted for mutation analysis with a diagnosis of dystrophinopathy. We report 1,111 mutations in the DMD gene, including 891 mutations with associated phenotypes. These results encompass 506 point mutations (including 294 nonsense mutations) and significantly expand the number of mutations associated with the dystrophinopathies, highlighting the utility of modern diagnostic techniques. Our data supports the uniform hypermutability of CGA>TGA mutations, establishes the frequency of polymorphic muscle (Dp427m) protein isoforms and reveals unique genomic haplotypes associated with "private" mutations. We note that 60% of these patients would be predicted to benefit from skipping of a single DMD exon using antisense oligonucleotide therapy, and 62% would be predicted to benefit from an inclusive multiexonskipping approach directed toward exons 45 through 55.
View details for DOI 10.1002/humu.21114
View details for Web of Science ID 000272796400007
View details for PubMedID 19937601
SNP Haplotype Mapping in a Small ALS Family PLOS ONE 2009; 4 (5)
The identification of genes for monogenic disorders has proven to be highly effective for understanding disease mechanisms, pathways and gene function in humans. Nevertheless, while thousands of Mendelian disorders have not yet been mapped there has been a trend away from studying single-gene disorders. In part, this is due to the fact that many of the remaining single-gene families are not large enough to map the disease locus to a single site in the genome. New tools and approaches are needed to allow researchers to effectively tap into this genetic gold-mine. Towards this goal, we have used haploid cell lines to experimentally validate the use of high-density single nucleotide polymorphism (SNP) arrays to define genome-wide haplotypes and candidate regions, using a small amyotrophic lateral sclerosis (ALS) family as a prototype. Specifically, we used haploid-cell lines to determine if high-density SNP arrays accurately predict haplotypes across entire chromosomes and show that haplotype information significantly enhances the genetic information in small families. Panels of haploid-cell lines were generated and a 5 centimorgan (cM) short tandem repeat polymorphism (STRP) genome scan was performed. Experimentally derived haplotypes for entire chromosomes were used to directly identify regions of the genome identical-by-descent in 5 affected individuals. Comparisons between experimentally determined and in silico haplotypes predicted from SNP arrays demonstrate that SNP analysis of diploid DNA accurately predicted chromosomal haplotypes. These methods precisely identified 12 candidate intervals, which are shared by all 5 affected individuals. Our study illustrates how genetic information can be maximized using readily available tools as a first step in mapping single-gene disorders in small families.
View details for DOI 10.1371/journal.pone.0005687
View details for Web of Science ID 000266331700014
View details for PubMedID 19479031
Congenital muscular dystrophy in a new age NEUROLOGY 2008; 71 (5): 308-309
Myotonic dystrophy type 2 in Japan: ancestral origin distinct from Caucasian families NEUROGENETICS 2008; 9 (1): 61-63
Myotonic dystrophy type 2 (DM2) is caused by expansion of a tetranucleotide CCTG repeat in intron 1 of the ZNF9 gene on chromosome 3q21. All studied DM2 mutations have been reported in Caucasians and share an identical haplotype, suggesting a common founder. We identified a Japanese patient with DM2 and showed that the affected haplotype is distinct from the previously identified DM2 haplotype shared among Caucasians. These data strongly suggest that DM2 expansion mutations originate from separate founders in Europe and Japan and are more widely distributed than previously recognized.
View details for DOI 10.1007/s10048-007-0110-4
View details for Web of Science ID 000252638800007
View details for PubMedID 18057971
Heterozygosity for a protein truncation mutation of sodium channel SCN8A in a patient with cerebellar atrophy, ataxia, and mental retardation JOURNAL OF MEDICAL GENETICS 2006; 43 (6): 527-530
The SCN8A gene on chromosome 12q13 encodes the voltage gated sodium channel Na(v)1.6, which is widely expressed in neurons of the CNS and PNS. Mutations in the mouse ortholog of SCN8A result in ataxia and other movement disorders.We screened the 26 coding exons of SCN8A in 151 patients with inherited or sporadic ataxia.A 2 bp deletion in exon 24 was identified in a 9 year old boy with mental retardation, pancerebellar atrophy, and ataxia. This mutation, Pro1719ArgfsX6, introduces a translation termination codon into the pore loop of domain 4, resulting in removal of the C-terminal cytoplasmic domain and predicted loss of channel function. Three additional heterozygotes in the family exhibit milder cognitive and behavioural deficits including attention deficit hyperactivity disorder (ADHD). No additional occurrences of this mutation were observed in 625 unrelated DNA samples (1250 chromosomes).The phenotypes of the heterozygous individuals suggest that mutations in SCN8A may result in motor and cognitive deficits of variable expressivity, but the study was limited by lack of segregation in the small pedigree and incomplete information about family members. Identification of additional families will be required to confirm the contribution of the SCN8A mutation to the clinical features in ataxia, cognition and behaviour disorders.
View details for DOI 10.1136/jmg.2005.035667
View details for Web of Science ID 000237973300011
View details for PubMedID 16236810
DM2 intronic expansions: evidence for CCUG accumulation without flanking sequence or effects on ZNF9 mRNA processing or protein expression HUMAN MOLECULAR GENETICS 2006; 15 (11): 1808-1815
Myotonic dystrophy type 2 (DM2) is caused by a CCTG expansion mutation in intron 1 of the zinc finger protein 9 (ZNF9) gene. The mean expansion size in patients is larger than for DM1 or any previously reported disorder (mean=5000 CCTGs; range=75-11 000), and similar to DM1, repeats containing ribonuclear inclusions accumulate in affected DM2 tissue. Although an RNA gain-of-function mechanism involving DM1 CUG or DM2 CCUG expansion transcripts is now well established, still debated are the potential role that flanking sequences within the DMPK 3'-UTR may have on disease pathogenesis and whether or not decreased expression of DMPK, ZNF9 or neighboring genes at these loci contribute to disease. To address these questions in DM2, we have examined the nucleic acid content of the ribonuclear inclusions and the effects of these large expansions on ZNF9 expression. Using cell lines either haploid or homozygous for the expansion, as well as skeletal muscle biopsy tissue, we demonstrate that pre-mRNAs containing large CCUG expansions are normally spliced and exported from the nucleus, that the expansions do not decrease ZNF9 expression at the mRNA or protein level, and that the ribonuclear inclusions are enriched for the CCUG expansion, but not intronic flanking sequences. These data suggest that the downstream molecular effects of the DM2 mutation are triggered by the accumulation of CCUG repeat tract alone.
View details for DOI 10.1093/hmg/ddl103
View details for Web of Science ID 000237696700007
View details for PubMedID 16624843
Spectrin mutations cause spinocerebellar ataxia type 5 NATURE GENETICS 2006; 38 (2): 184-190
We have discovered that beta-III spectrin (SPTBN2) mutations cause spinocerebellar ataxia type 5 (SCA5) in an 11-generation American kindred descended from President Lincoln's grandparents and two additional families. Two families have separate in-frame deletions of 39 and 15 bp, and a third family has a mutation in the actin/ARP1 binding region. Beta-III spectrin is highly expressed in Purkinje cells and has been shown to stabilize the glutamate transporter EAAT4 at the surface of the plasma membrane. We found marked differences in EAAT4 and GluRdelta2 by protein blot and cell fractionation in SCA5 autopsy tissue. Cell culture studies demonstrate that wild-type but not mutant beta-III spectrin stabilizes EAAT4 at the plasma membrane. Spectrin mutations are a previously unknown cause of ataxia and neurodegenerative disease that affect membrane proteins involved in glutamate signaling.
View details for DOI 10.1038/ng1728
View details for Web of Science ID 000234953200012
View details for PubMedID 16429157
Gene symbol: SCN8A. Disease: Ataxia. Accession #Hd0520. Human genetics 2006; 118 (6): 776-?
Dominant non-coding repeat expansions in human disease. Genome dynamics 2006; 1: 67-83
The general model that dominant diseases are caused by mutations that result in a gain or change in function of the corresponding protein was challenged by the discovery that the myotonic dystrophy type 1 mutation is a CTG expansion located in the 3' untranslated portion of a kinase gene. The subsequent discovery that a similar transcribed but untranslated CCTG expansion in an intron causes the same multisystemic features in myotonic dystrophy type 2 (DM2), along with other developments in the DM1 field, demonstrate a mechanism in which these expansion mutations cause disease through a gain of function mechanism triggered by the accumulation of transcripts containing CUG or CCUG repeat expansions. A similar RNA gain of function mechanism has also been implicated in fragile X tremor ataxia syndrome (FXTAS) and may play a role in pathogenesis of other non-coding repeat expansion diseases, including spinocerebellar ataxia type 8 (SCA8), SCA10, SCA12 and Huntington disease-like 2.
View details for DOI 10.1159/000092501
View details for PubMedID 18724054
Genetics and molecular pathogenesis of the myotonic dystrophies. Current neurology and neuroscience reports 2005; 5 (1): 55-59
Pathogenic repeat expansions were initially identified as causing either a loss of gene product, such as in fragile X mental retardation, or an expansion of a polyglutamine region of a protein, as was first shown in spinobulbar muscular atrophy (Kennedy's disease). The pathogenic effect of the repeat expansion in myotonic dystrophy type 1, however, has been controversial because it does not encode a protein but nonetheless results in a highly penetrant dominant disease. Clinical and molecular characterization of myotonic dystrophy types 1 and 2 have now demonstrated a novel disease mechanism involving pathogenic effects of repeat expansions that are expressed in RNA but are not translated into protein.
View details for PubMedID 15676109
RNA pathogenesis of the myotonic dystrophies NEUROMUSCULAR DISORDERS 2005; 15 (1): 5-16
Myotonic dystrophy (dystrophia myotonica, DM) is the most common form of muscular dystrophy in adults. The presence of two genetic forms of this complex multisystemic disease (DM1 and DM2) was unrecognized until the genetic cause of DM1 was identified in 1992. The fact that the DM1 mutation is an untranslated CTG expansion led to extended controversy about the molecular pathophysiology of this disease. When the DM2 mutation was identified in 2001 as being a similarly untranslated CCTG expansion, the molecular and clinical parallels between DM1 and DM2 substantiated the role of a novel mechanism in generating the unusual constellation of clinical features seen in these diseases: the repeat expansions expressed at the RNA level alter RNA processing, at least in part by interfering with alternative splicing of other genes. For example, in both DM1 and DM2, altered splicing of chloride channel and insulin receptor transcripts leads to myotonia and insulin resistance, respectively. Although other mechanisms may underlie the differences between DM1 and DM2, the pathogenic effects of the RNA mechanism are now clear, which will facilitate development of appropriate treatments.
View details for DOI 10.1016/j.nmd.2004.09.012
View details for Web of Science ID 000226567900002
View details for PubMedID 15639115
Sudden cardiac death in myotonic dystrophy type 2 NEUROLOGY 2004; 63 (12): 2402-2404
Medical records and follow-up data were reviewed in 297 genetically proven myotonic dystrophy type 2 (DM2) patients. Patients were selected by the criteria of cardiac sudden death before age 45. Sudden death occurred in four patients, three of whom were cardiological asymptomatic, and one with a history of heart failure. Cardiac histopathology showed dilated cardiomyopathy in all, and conduction system fibrosis in two patients. Pathogenetic CCUG ribonuclear inclusions were demonstrable in cardiomyocytes.
View details for Web of Science ID 000226010000039
View details for PubMedID 15623712
Spinocerebellar ataxia type 8: Molecular genetic comparisons and haplotype analysis of 37 families with ataxia AMERICAN JOURNAL OF HUMAN GENETICS 2004; 75 (1): 3-16
We reported elsewhere that an untranslated CTG expansion causes the dominantly inherited neurodegenerative disorder spinocerebellar ataxia type 8 (SCA8). SCA8 shows a complex inheritance pattern with extremes of incomplete penetrance, in which often only one or two affected individuals are found in a given family. SCA8 expansions have also been found in control chromosomes, indicating that separate genetic or environmental factors increase disease penetrance among SCA8-expansion-carrying patients with ataxia. We describe the molecular genetic features and disease penetrance of 37 different families with SCA8 ataxia from the United States, Canada, Japan, and Mexico. Haplotype analysis using 17 STR markers spanning an approximately 1-Mb region was performed on the families with ataxia, on a group of expansion carriers in the general population, and on psychiatric patients, to clarify the genetic basis of the reduced penetrance and to investigate whether CTG expansions among different populations share a common ancestral background. Two major ancestrally related haplotypes (A and A') were found among white families with ataxia, normal controls, and patients with major psychosis, indicating a common ancestral origin of both pathogenic and nonpathogenic SCA8 expansions among whites. Two additional and distinct haplotypes were found among a group of Japanese families with ataxia (haplotype B) and a Mexican family with ataxia (haplotype C). Our finding that SCA8 expansions on three independently arising haplotypes are found among patients with ataxia and cosegregate with ataxia when multiple family members are affected further supports the direct role of the CTG expansion in disease pathogenesis.
View details for Web of Science ID 000222031300002
View details for PubMedID 15152344
Myotonic dystrophy: RNA pathogenesis comes into focus AMERICAN JOURNAL OF HUMAN GENETICS 2004; 74 (5): 793-804
Myotonic dystrophy (DM)--the most common form of muscular dystrophy in adults, affecting 1/8000 individuals--is a dominantly inherited disorder with a peculiar and rare pattern of multisystemic clinical features affecting skeletal muscle, the heart, the eye, and the endocrine system. Two genetic loci have been associated with the DM phenotype: DM1, on chromosome 19, and DM2, on chromosome 3. In 1992, the mutation responsible for DM1 was identified as a CTG expansion located in the 3' untranslated region of the dystrophia myotonica-protein kinase gene (DMPK). How this untranslated CTG expansion causes myotonic dystrophy type 1(DM1) has been controversial. The recent discovery that myotonic dystrophy type 2 (DM2) is caused by an untranslated CCTG expansion, along with other discoveries on DM1 pathogenesis, indicate that the clinical features common to both diseases are caused by a gain-of-function RNA mechanism in which the CUG and CCUG repeats alter cellular function, including alternative splicing of various genes. We discuss the pathogenic mechanisms that have been proposed for the myotonic dystrophies, the clinical and molecular features of DM1 and DM2, and the characterization of murine and cell-culture models that have been generated to better understand these diseases.
View details for Web of Science ID 000220926100002
View details for PubMedID 15065017
Rapid resolution of quadriplegic CIDP by combined plasmapheresis and IVIg NEUROLOGY 2004; 62 (1): 155-156
Myotonic dystrophy type 2: Human founder haplotype and evolutionary conservation of the repeat tract AMERICAN JOURNAL OF HUMAN GENETICS 2003; 73 (4): 849-862
Myotonic dystrophy (DM), the most common form of muscular dystrophy in adults, can be caused by a mutation on either chromosome 19 (DM1) or 3 (DM2). In 2001, we demonstrated that DM2 is caused by a CCTG expansion in intron 1 of the zinc finger protein 9 (ZNF9) gene. To investigate the ancestral origins of the DM2 expansion, we compared haplotypes for 71 families with genetically confirmed DM2, using 19 short tandem repeat markers that we developed that flank the repeat tract. All of the families are white, with the majority of Northern European/German descent and a single family from Afghanistan. Several conserved haplotypes spanning >700 kb appear to converge into a single haplotype near the repeat tract. The common interval that is shared by all families with DM2 immediately flanks the repeat, extending up to 216 kb telomeric and 119 kb centromeric of the CCTG expansion. The DM2 repeat tract contains the complex repeat motif (TG)(n)(TCTG)(n)(CCTG)(n). The CCTG portion of the repeat tract is interrupted on normal alleles, but, as in other expansion disorders, these interruptions are lost on affected alleles. We examined haplotypes of 228 control chromosomes and identified a potential premutation allele with an uninterrupted (CCTG)(20) on a haplotype that was identical to the most common affected haplotype. Our data suggest that the predominant Northern European ancestry of families with DM2 resulted from a common founder and that the loss of interruptions within the CCTG portion of the repeat tract may predispose alleles to further expansion. To gain insight into possible function of the repeat tract, we looked for evolutionary conservation. The complex repeat motif and flanking sequences within intron 1 are conserved among human, chimpanzee, gorilla, mouse, and rat, suggesting a conserved biological function.
View details for Web of Science ID 000185676100012
View details for PubMedID 14505273
Autoimmune rippling muscle NEUROLOGY 2003; 61 (6): 869-870
Myotonic dystrophy type 2 - Molecular, diagnostic and clinical spectrum NEUROLOGY 2003; 60 (4): 657-664
Myotonic dystrophy types 1 (DM1) and 2 (DM2/proximal myotonic myopathy PROMM) are dominantly inherited disorders with unusual multisystemic clinical features. The authors have characterized the clinical and molecular features of DM2/PROMM, which is caused by a CCTG repeat expansion in intron 1 of the zinc finger protein 9 (ZNF9) gene.Three-hundred and seventy-nine individuals from 133 DM2/PROMM families were evaluated genetically, and in 234 individuals clinical and molecular features were compared.Among affected individuals 90% had electrical myotonia, 82% weakness, 61% cataracts, 23% diabetes, and 19% cardiac involvement. Because of the repeat tract's unprecedented size (mean approximately 5,000 CCTGs) and somatic instability, expansions were detectable by Southern analysis in only 80% of known carriers. The authors developed a repeat assay that increased the molecular detection rate to 99%. Only 30% of the positive samples had single sizeable expansions by Southern analysis, and 70% showed multiple bands or smears. Among the 101 individuals with single expansions, repeat size did not correlate with age at disease onset. Affected offspring had markedly shorter expansions than their affected parents, with a mean size difference of -17 kb (-4,250 CCTGs).DM2 is present in a large number of families of northern European ancestry. Clinically, DM2 resembles adult-onset DM1, with myotonia, muscular dystrophy, cataracts, diabetes, testicular failure, hypogammaglobulinemia, and cardiac conduction defects. An important distinction is the lack of a congenital form of DM2. The clinical and molecular parallels between DM1 and DM2 indicate that the multisystemic features common to both diseases are caused by CUG or CCUG expansions expressed at the RNA level.
View details for Web of Science ID 000182948000024
View details for PubMedID 12601109
Molecular genetics of spinocerebellar ataxia type 8 (SCA8) CYTOGENETIC AND GENOME RESEARCH 2003; 100 (1-4): 175-183
We previously reported that a transcribed but untranslated CTG expansion causes a novel form of ataxia, spinocerebellar ataxia type 8 (SCA8) (Koob et al., 1999). SCA8 was the first example of a dominant spinocerebellar ataxia that is not caused by the expansion of a CAG repeat translated into a polyglutamine tract. This slowly progressive form of ataxia is characterized by dramatic repeat instability and a high degree of reduced penetrance. The clinical and genetic features of the disease are discussed below.
View details for DOI 10.1159/000072852
View details for Web of Science ID 000186274900018
View details for PubMedID 14526178
Randomized, controlled trial of intravenous immunoglobulin in myasthenia gravis MUSCLE & NERVE 2002; 26 (4): 549-552
We initiated a randomized, double-blinded, placebo-controlled trial of intravenous immunoglobulin (IVIG) treatment in myasthenia gravis (MG). Patients received IVIG 2 gm/kg at induction and 1 gm/kg after 3 weeks vs. 5% albumin placebo. The primary efficacy measurement was the change in the quantitative MG Score (QMG) at day 42. Fifteen patients were enrolled (6 to IVIG; 9 to placebo) before the study was terminated because of insufficient IVIG inventories. At day 42, there was no significant difference in primary or secondary outcome measurements between the two groups. In a subsequent 6-week open-label study of IVIG, positive trends were observed.
View details for DOI 10.1002/mus.10224
View details for Web of Science ID 000178385500016
View details for PubMedID 12362423
Myotonic dystrophy: clinical and molecular parallels between myotonic dystrophy type 1 and type 2. Current neurology and neuroscience reports 2002; 2 (5): 465-470
Myotonic dystrophy (DM) is a dominantly inherited disorder with a peculiar pattern of multisystemic clinical features affecting skeletal muscle, the heart, the eye, and the endocrine system. Two genetic loci have been associated with the DM phenotype: DM1 on chromosome 19, and DM2 on chromosome 3. In 1992, the mutation responsible for DM1 was identified as a CTG expansion located in the 3' untranslated region of the dystrophica myotonica-protein kinase gene (DMPK). How this untranslated CTG expansion causes DM1 has been a matter of controversy. The recent discovery that DM2 is caused by an untranslated CCTG expansion, along with other discoveries on DM1 pathogenesis, indicate that the clinical features common to both diseases are caused by a gain of function RNA mechanism in which the CUG and CCUG repeats alter cellular function, including alternative splicing of various genes.
View details for PubMedID 12169228
Force assessment in periodic paralysis after electrical muscle stimulation MAYO CLINIC PROCEEDINGS 2002; 77 (3): 232-240
To obtain an objective measure of muscle force in periodic paralysis, we studied ankle dorsiflexion torque during induced paralytic attacks in hyperkalemic and hypokalemic patients. SUBJECTS, PATIENTS, AND METHODS: Dorsiflexor torque after peroneal nerve stimulation was recorded during provocative tests on 5 patients with hypokalemic or hyperkalemic disorders and on 2 control subjects (1995-2001). Manual strength assessment was simultaneously performed in a blinded fashion. Standardized provocation procedures were used.The loss of torque in hyperkalemic patients roughly paralleled the loss of clinically detectable strength, whereas in the hypokalemic patients, pronounced torque loss occurred well before observed clinical effects. No dramatic changes occurred in the control subjects. Torque amplitude decreased more than 70% in all patients during the provocation tests; such decreases were associated with alterations induced in serum potassium concentrations.Stimulated torque measurement offers several advantages in characterizing muscle dysfunction in periodic paralysis: (1) it is independent of patient effort; (2) it can show a definitely abnormal response early during provocative maneuvers; and (3) characteristics of muscle contraction can be measured that are unobservable during voluntary contraction. Stimulated torque measurements can characterize phenotypic muscle function in neuromuscular diseases.
View details for Web of Science ID 000174132800005
View details for PubMedID 11888026
Myotonic dystrophy type 2 caused by a CCTG expansion in intron 1 of ZNF9 SCIENCE 2001; 293 (5531): 864-867
Myotonic dystrophy (DM), the most common form of muscular dystrophy in adults, can be caused by a mutation on either chromosome 19q13 (DM1) or 3q21 (DM2/PROMM). DM1 is caused by a CTG expansion in the 3' untranslated region of the dystrophia myotonica-protein kinase gene (DMPK). Several mechanisms have been invoked to explain how this mutation, which does not alter the protein-coding portion of a gene, causes the specific constellation of clinical features characteristic of DM. We now report that DM2 is caused by a CCTG expansion (mean approximately 5000 repeats) located in intron 1 of the zinc finger protein 9 (ZNF9) gene. Parallels between these mutations indicate that microsatellite expansions in RNA can be pathogenic and cause the multisystemic features of DM1 and DM2.
View details for Web of Science ID 000170241000045
View details for PubMedID 11486088
Clinical illness due to parvovirus B19 infection after infusion of solvent/detergent-treated pooled plasma TRANSFUSION 2000; 40 (10): 1203-1206
Lipid-enveloped viruses such as HIV, HBV, and HCV can be inactivated by treatment with solvents and detergents. HAV and human parvovirus B19 lack lipid envelopes and are not inactivated. Solvent/detergent-treated pooled plasma (S/D plasma) contains neutralizing antibodies, but it is not known whether the parvovirus B19 antibody content is sufficient to prevent transmission of the disease. A patient is described who developed a clinical illness due to parvovirus B19 infection after the infusion of S/D plasma.A 36-year-old woman with myasthenia gravis underwent five plasma exchange procedures from January 15 to January 25, 1999, using albumin, except for 5 units of SD plasma given because of a low fibrinogen level. Four of the 5 units were implicated in a recall after high levels of parvovirus B19 DNA were found in several lots. Two weeks after the infusion, the patient developed fatigue, a rash, and severe polyarthralgias. Parvovirus B19 IgG and IgM antibody titers were consistent with an acute infection.Clinically apparent parvovirus B19 infection can follow the use of S/D plasma that contains high levels of parvovirus B19 DNA.
View details for Web of Science ID 000089844200011
View details for PubMedID 11061856
Spinocerebellar ataxia type 8 - Clinical features in a large family NEUROLOGY 2000; 55 (5): 649-657
To compare the clinical and genetic features of the seven-generation family (MN-A) used to define the spinocerebellar ataxia 8 (SCA8) locus.The authors recently described an untranslated CTG expansion that causes a novel form of SCA (SCA8) characterized by reduced penetrance and complex patterns of repeat instability.Clinical and molecular features of 82 members of the MN-A family were evaluated by neurologic examination, quantitative dexterity testing, and, in some individuals, MRI and sperm analyses.SCA8 is a slowly progressive, predominantly cerebellar ataxia with marked cerebellar atrophy, affecting gait, swallowing, speech, and limb and eye movements. CTG tracts are longer in affected (mean = 116 CTG repeats) than in unaffected expansion carriers (mean = 90, p < 10-8). Quantitative dexterity testing did not detect even subtle signs of ataxia in unaffected expansion carriers. Surprisingly, all 21 affected MN-A family members inherited an expansion from their mothers. The maternal penetrance bias is consistent with maternal repeat expansions yielding alleles above the pathogenic threshold in the family (>107 CTG) and paternal contractions resulting in shorter alleles. Consistent with the reduced penetrance of paternal transmissions, CTG tracts in all or nearly all sperm (84 to 99) are significantly shorter than in the blood (116) of an affected man.The biologic relationship between repeat length and ataxia indicates that the CTG repeat is directly involved in SCA8 pathogenesis. Diagnostic testing and genetic counseling are complicated by the reduced penetrance, which often makes the inheritance appear recessive or sporadic, and by interfamilial differences in the length of a stable (CTA)n tract preceding the CTG repeat.
View details for Web of Science ID 000089484700010
View details for PubMedID 10980728
SCA8 CTG repeat: en masse contractions in sperm and intergenerational sequence changes may play a role in reduced penetrance HUMAN MOLECULAR GENETICS 2000; 9 (14): 2125-2130
We recently described an untranslated CTG expansion that causes a previously undescribed form of spinocerebellar ataxia (SCA8). The SCA8 CTG repeat is preceded by a polymorphic but stable CTA tract, with the configuration (CTA)(1-21)(CTG)(n). The CTG portion of the repeat is elongated on pathogenic alleles, which nearly always change in size when transmitted from generation to generation. To better understand the reduced penetrance and maternal penetrance bias associated with SCA8 we analyzed the sequence configurations and instability patterns of the CTG repeat in affected and unaffected family members. In contrast to other triplet repeat diseases, expanded alleles found in affected SCA8 individuals can have either a pure uninterrupted CTG repeat tract or an allele with one or more CCG, CTA, CTC, CCA or CTT interruptions. Surprisingly, we found six different sequence configurations of the CTG repeat on expanded alleles in a seven generation family. In two instances duplication of CCG interruptions occurred over a single generation and in other instances duplications that had occurred in different branches of the family could be inferred. We also evaluated SCA8 instability in sperm samples from individuals with expansions ranging in size from 80 to 800 repeats in blood. Surprisingly the SCA8 repeat tract in sperm underwent contractions, with nearly all of the resulting expanded alleles having repeat lengths of <100 CTGs, a size that is not often associated with disease. These en masse repeat contractions in sperm likely underlie the reduced penetrance associated with paternal transmission.
View details for Web of Science ID 000089181300007
View details for PubMedID 10958651
New nomenclature and DNA testing guidelines for myotonic dystrophy type 1(DM1) NEUROLOGY 2000; 54 (6): 1218-1221
Adult-onset "infant" botulism: An unusual cause of weakness in the intensive care unit NEUROLOGY 1999; 53 (4): 891-891
Clinical and genetic characteristics of a five-generation family with a novel form of myotonic dystrophy (DM2) NEUROMUSCULAR DISORDERS 1999; 9 (1): 19-27
We report the clinical and genetic characteristics of a five-generation family (MN1) with an unusual form of myotonic dystrophy (DM). Affected individuals have clinical features that are similar to DM including myotonia, distal weakness, frontal balding, polychromatic cataracts, infertility and cardiac arrhythmias. Genetic analyses reveal that affected individuals do not have the CTG expansion associated with DM, nor is the disease locus linked to the DM region of chromosome 19. We have also excluded the MN1 disease locus from the chromosomal regions containing the genes for the muscle sodium (alpha- and beta-subunits) and chloride channels, both of which are involved in other myotonic disorders. We have recently mapped the disease locus (DM2) in this family to a 10 cM region of chromosome 3q [Ranum LPW, Rasmussen PF, Benzow KA, Koob MD, Day JW. Nat Genet 1998;19:196-198]. The genetically distinct form of myotonic dystrophy in the MN1 kindred shares some of the clinical features of previously reported families with proximal myotonic myopathy (PROMM). The size of the MN1 family (25 affected individuals) makes it a unique resource for both clinical and genetic studies. This second form of myotonic dystrophy may help resolve the confusion that remains about how the CTG repeat expansion in the 3' untranslated portion of the myotonin protein kinase gene causes the multisystem involvement of DM.
View details for Web of Science ID 000078636800004
View details for PubMedID 10063831
Genetic mapping of a second myotonic dystrophy locus NATURE GENETICS 1998; 19 (2): 196-198
We report the mapping of a second myotonic dystrophy locus, myotonic dystrophy type 2 (DM2). Myotonic dystrophy (DM) is a multi-system disease and the most common form of muscular dystrophy in adults. In 1992, DM was shown to be caused by an expanded CTG repeat in the 3' untranslated region of the dystrophia myotonica-protein kinase gene (DMPK) on chromosome 19 (refs 2-6). Although several theories have been put forth to explain how the CTG expansion causes the broad spectrum of clinical features associated with DM, it is not understood how this mutation, which does not alter the protein-coding region of a gene, causes an affect at the cellular level. We have identified a five-generation family (MN1) with a genetically distinct form of myotonic dystrophy. Affected members exhibit remarkable clinical similarity to DM (myotonia, proximal and distal limb weakness, frontal balding, cataracts and cardiac arrhythmias) but do not have the chromosome-19 D CTG expansion. We have mapped the disease locus (DM2) of the MN1 family to a 10-cM region of chromosome 3q. Understanding the common molecular features of two different forms of the disease should shed light on the mechanisms responsible for the broad constellation of seemingly unrelated clinical features present in both diseases.
View details for Web of Science ID 000073865100032
View details for PubMedID 9620781
Genetic manipulation of AChR responses suggests multiple causes of weakness in slow-channel syndrome. Annals of the New York Academy of Sciences 1998; 841: 167-180
Rapid cloning of expanded trinucleotide repeat sequences from genomic DNA NATURE GENETICS 1998; 18 (1): 72-75
Trinucleotide repeat expansions have been shown to cause a number of neurodegenerative diseases. A hallmark of most of these diseases is the presence of anticipation, a decrease in the age at onset in consecutive generations due to the tendency of the unstable trinucleotide repeat to lengthen when passed from one generation to the next. The involvement of trinucleotide repeat expansions in a number of other diseases--including familial spastic paraplegia, schizophrenia, bipolar affective disorder and spinocerebellar ataxia type 7 (SCA7; ref. 10)--is suggested both by the presence of anticipation and by repeat expansion detection (RED) analysis of genomic DNA samples. The involvement of trinucleotide expansions in these diseases, however, can be conclusively confirmed only by the isolation of the expansions present in these populations and detailed analysis to assess each expansion as a possible pathogenic mutation. We describe a novel procedure for quick isolation of expanded trinucleotide repeats and the corresponding flanking nucleotide sequence directly from small amounts of genomic DNA by a process of Repeat Analysis, Pooled Isolation and Detection of individual clones containing expanded trinucleotide repeats (RAPID cloning). We have used this technique to clone the pathogenic SCA7 CAG expansion from an archived DNA sample of an individual affected with ataxia and retinal degeneration.
View details for Web of Science ID 000071259600026
View details for PubMedID 9425905
Desensitization of mutant acetylcholine receptors in transgenic mice reduces the amplitude of neuromuscular synaptic currents SYNAPSE 1997; 27 (4): 367-377
While the slow onset of desensitization of nicotinic acetylcholine receptors (AChRs), relative to the rate of acetylcholine removal, excludes this kinetic state from shaping synaptic responses in normal neuromuscular transmission, its role in neuromuscular disorders has not been examined. The slow-channel congenital myasthenic syndrome (SCCMS) is a disorder caused by point mutations in the AChR subunit-encoding genes leading to kinetically abnormal (slow) channels, reduced miniature endplate current amplitudes (MEPCs), and degeneration of the postsynaptic membrane. Because of this complicated picture of kinetic and structural change in the neuromuscular junction, it is difficult to assess the importance of the multiple factors that may be responsible for the reduced endplate current amplitudes, and ultimately the clinical syndrome. In order to address this we have used a transgenic mouse model for the SCCMS that has slow AChR ion channels and reduced endplate responsiveness in the absence of any of the degenerative changes. We found that the reduction in MEPC amplitudes in these mice could not be explained by either reduced AChR number or by reduced AChR channel conductance. Rather, we found that the mutant AChRs in situ manifested an activity-dependent reduction in sensitivity that caused diminished MEPC and endplate current amplitude with nerve stimulation. This observation demonstrates that the basis for the reduction in MEPC amplitudes in the SCCMS may be multifactorial. Moreover, these findings demonstrate that, under conditions that alter their rate of desensitization, the kinetic properties of nicotinic AChRs can control the strength of synaptic responses.
View details for Web of Science ID A1997YE82600010
View details for PubMedID 9372559
Slow-channel transgenic mice: A model of postsynaptic organellar degeneration at the neuromuscular junction JOURNAL OF NEUROSCIENCE 1997; 17 (11): 4170-4179
The slow-channel congenital myasthenic syndrome (SCCMS) is a dominantly inherited disorder of neuromuscular transmission characterized by delayed closure of the skeletal muscle acetylcholine receptor (AChR) ion channel and degeneration of the neuromuscular junction. The identification of a series of AChR subunit mutations in the SCCMS supports the hypothesis that the altered kinetics of the endplate currents in this disease are attributable to inherited abnormalities of the AChR. To investigate the role of these mutant AChR subunits in the development of the synaptic degeneration seen in the SCCMS, we have studied the properties of the AChR mutation, epsilonL269F, found in a family with SCCMS, using both in vitro and in vivo expression systems. The mutation causes a sixfold increase in the open time of AChRs expressed in vitro, similar to the phenotype of other reported mutants. Transgenic mice expressing this mutant develop a syndrome that is highly reminiscent of the SCCMS. Mice have fatigability of limb muscles, electrophysiological evidence of slow AChR ion channels, and defective neuromuscular transmission. Pathologically, the motor endplates show focal accumulation of calcium and striking ultrastructural changes, including enlargement and degeneration of the subsynaptic mitochondria and nuclei. These findings clearly demonstrate the role of this mutation in the spectrum of abnormalities associated with the SCCMS and point to the subsynaptic organelles as principal targets in this disease. These transgenic mice provide a useful model for the study of excitotoxic synaptic degeneration.
View details for Web of Science ID A1997XA05600021
View details for PubMedID 9151734
An improved method for muscle force neuromuscular disease assessment JOURNAL OF MEDICAL ENGINEERING & TECHNOLOGY 1996; 20 (2): 67-74
We describe here the reliability and validity of methods to quantify involuntary muscle torque induced by non-invasive nerve stimulation. A rigid apparatus was used to hold the subject's limb in a predetermined position and confine movement to a specific direction (i.e. ankle dorsiflexion or thumb adduction). An incorporated strain gauge was used to measure isometric torque, and all data were recorded by a data acquisition program. The innervating nerves were stimulated by surface electrodes, using either single stimuli to generate a twitch, or short trains of stimuli to produce tetanic contraction of the individual muscle under study. The average peak tetanic torque generated by the dorsiflexor muscles in healthy control was 20.4 +/- 3.8 Nm and varied by 3.7% with repeated testing. The mean torque generated by the adductor pollicis muscle in controls was 1.5 +/- 0.4 Nm and varied by 4.6% with repeated testing. In patient populations significant changes in activated torque were readily quantified, and the effects of treatment can be easily assessed. Furthermore, several specific parameters of recorded isometric contractions were measured; e.g. time between stimulus and torque onset, peak rate of torque development, time to peak torque, half-relaxation time, and others (none of which are measurable when using voluntary contraction of muscle). Compared to current assessment methods, monitoring muscle torque generated by nerve stimulation improves objectivity, reliability, and quantitative capabilities. The presented method has significant potential both in diagnosing neuromuscular disorders and determining treatment efficacy.
View details for Web of Science ID A1996UY85000003
View details for PubMedID 8836925
Transgenic mouse model of the slow-channel syndrome MUSCLE & NERVE 1996; 19 (1): 79-87
To investigate the effect of acetylcholine receptor (AChR) mutations on neuromuscular transmission and to develop a model for the human neuromuscular disease, the slow-channel syndrome, we generated transgenic mice with abnormal AChRs using a delta subunit with a mutation in the ion channel domain. In three transgenic lines, nerve-evoked end-plate currents and spontaneous miniature end-plate currents (MEPCs) had prolonged decay phases and MEPC amplitudes were reduced by 33%. Single nerve stimuli elicited repetitive compound muscle action potentials in vivo. Transgenic mice were abnormally sensitive to the neuromuscular blocker, curare. These observations demonstrate that we can predictably alter AChR function, synaptic responses, and muscle fiber excitation in vivo by overexpressing subunits containing well-defined mutations. Furthermore these data support the hypothesis that the electrophysiological findings in the neuromuscular disorder, the slow-channel syndrome, are due to mutant AChRs.
View details for Web of Science ID A1996TM00100013
View details for PubMedID 8538674
NICOTINIC ACETYLCHOLINE-RECEPTOR DESENSITIZATION IS REGULATED BY ACTIVATION-INDUCED EXTRACELLULAR ADENOSINE ACCUMULATION JOURNAL OF NEUROSCIENCE 1992; 12 (11): 4540-4544
Adenosine modulation of nicotinic ACh receptor (nAChR) function was studied in primary cultures of rat skeletal muscle. Activation of the nAChR by carbachol increased extracellular adenosine concentration in a dose-dependent manner. Furthermore, carbachol activation of the nicotinic receptor resulted in a twofold increase in cAMP levels in the muscle cells. The carbachol-dependent increase in cAMP levels was inhibited by adenosine receptor antagonists as well as by nicotinic receptor antagonists. These results suggest that the increased cAMP levels were due to adenosine receptor activation by the extracellular adenosine accumulated on nAChR activation. Others have shown that desensitization of the nAChR by agonist is mediated, in part, by phosphorylation. Since we found that nicotinic cholinergic agonists also cause adenosine accumulation with concomitant cAMP increases, we determined whether the accumulated adenosine has a role in desensitization. We found that the adenosine receptor antagonist, BW1434U, significantly inhibited carbachol-induced nAChR desensitization, indicating that extracellular adenosine is involved in nAChR desensitization. Our data suggest that nAChR function is regulated via a feedback mechanism mediated by adenosine released from muscle on activation of the nAChR.
View details for Web of Science ID A1992JY18800034
View details for PubMedID 1331363
NORMOCALCEMIC TETANY ABOLISHED BY CALCIUM INFUSION ANNALS OF NEUROLOGY 1990; 27 (4): 438-440
Tetany is a disorder of increased neuronal excitability usually associated with hypocalcemia. We studied a patient with typical tetanic cramps that responded to intravenous infusion of calcium despite normal serum concentrations of total and ionized calcium. Three generations were affected by similar symptoms, suggesting that this is a dominantly inherited disorder of neuronal hyperirritability.
View details for Web of Science ID A1990CZ77200012
View details for PubMedID 2353799
THUNDERCLAP HEADACHE - SYMPTOM OF UNRUPTURED CEREBRAL ANEURYSM LANCET 1986; 2 (8518): 1247-1248
Many patients with a ruptured berry aneurysm report an intense sentinel headache of sudden onset in the weeks before rupture. Such headaches have been attributed to a leak of blood, which implies that partial rupture has occurred. A case is reported of a patient who had severe headaches which seemed to be caused by an unruptured cerebral aneurysm, accompanied by diffuse cerebral vasospasm. Headache episodes with the thunderclap profile may require angiography for diagnosis even if the cerebrospinal fluid is bloodless.
View details for Web of Science ID A1986E984600005
View details for PubMedID 2878133
TIME COURSE OF MINIATURE POSTSYNAPTIC POTENTIALS AT THE MAUTHNER FIBER GIANT SYNAPSE OF THE HATCHETFISH BRAIN RESEARCH 1985; 325 (1-2): 115-128
The hatchetfish Mauthner fiber is presynaptic to 8-14 large myelinated axons in the medulla; the large ('giant') synapses formed by these fibers appear to be nicotinic cholinergic. Miniature postsynaptic potentials (mPSPs) were recorded from single identified synapses. The mPSPs were averaged to more accurately determine their shape; the rise time was approximately 70 microseconds, and the fall usually was biphasic with time constants of decay for the two phases of 280 and 800 microseconds. In 25% of the records analyzed a third, slow tail of decay was seen which had an average decay constant of 4.2 ms. The biphasic decay of mPSPs largely accounts for the similar shape of the postsynaptic current following a presynaptic impulse, which is described in the accompanying paper.
View details for Web of Science ID A1985ABG2900013
View details for PubMedID 2983824
POSTSYNAPTIC CURRENTS AT THE MAUTHNER FIBER GIANT SYNAPSE OF THE HATCHETFISH BRAIN RESEARCH 1985; 325 (1-2): 129-141
Postsynaptic currents (PSCs) at the giant synapse between Mauthner and giant fibers of the hatchetfish Gasteropelecus were studied under voltage clamp. This axo-axonic synapse lies in the central nervous system beneath the floor of the 4th ventricle where electrodes can be closely positioned both pre- and postsynaptically. Transmission is nicotonic cholinergic. The PSCs produced by Mauthner fiber impulses rise rapidly to a peak and decay in two phases; an early more rapid phase is followed by a late slower phase. The slope conductance of the peak amplitude of the PSCs declines at more inside positive potentials. The late phase of decay is exponential and voltage dependent, becoming faster for PSCs evoked at more inside positive potentials. At potentials positive to about -40 mV the late phase merges with the early phase. The decay rate constant of the slowest phase is exponentially related to voltage for potentials negative to about -10 mV, but becomes less voltage dependent for more positive potentials. The peak current is independent of whether it is evoked during inward or outward active currents of the electrically excitable membrane, and two phase decays are observed in PSCs of reduced quantal content. Thus, changes in slope conductance and two phase decays are not due to series resistance or interactions between quanta. PSCs can be modeled by a 3 state reaction scheme in which closed channels open when they bind transmitter and then can pass to a second closed state with receptor still bound such that they must return through the open state before losing their transmitter and returning to the resting, closed state.
View details for Web of Science ID A1985ABG2900014
View details for PubMedID 2983825
POSTSYNAPTIC DEPRESSION OF MAUTHNER CELL-MEDIATED STARTLE REFLEX, A POSSIBLE CONTRIBUTOR TO HABITUATION BRAIN RESEARCH 1980; 188 (1): 261-268