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1.
bioRxiv ; 2024 May 08.
Article in English | MEDLINE | ID: mdl-38903061

ABSTRACT

Pathogenic variants in HMGCR were recently linked to a limb-girdle muscular dystrophy (LGMD) phenotype. The protein product HMG CoA reductase (HMGCR) catalyzes a key component of the cholesterol synthesis pathway. The two other muscle diseases associated with HMGCR, statin-associated myopathy (SAM) and autoimmune anti-HMGCR myopathy, are not inherited in a Mendelian pattern. The mechanism linking pathogenic variants in HMGCR with skeletal muscle dysfunction is unclear. We knocked down Hmgcr in mouse skeletal myoblasts, knocked down hmgcr in Drosophila, and expressed three pathogenic HMGCR variants (c.1327C>T, p.Arg443Trp; c.1522_1524delTCT, p.Ser508del; and c.1621G>A, p.Ala541Thr) in Hmgcr knockdown mouse myoblasts. Hmgcr deficiency was associated with decreased proliferation, increased apoptosis, and impaired myotube fusion. Transcriptome sequencing of Hmgcr knockdown versus control myoblasts revealed differential expression involving mitochondrial function, with corresponding differences in cellular oxygen consumption rates. Both ubiquitous and muscle-specific knockdown of hmgcr in Drosophila led to lethality. Overexpression of reference HMGCR cDNA rescued myotube fusion in knockdown cells, whereas overexpression of the pathogenic variants of HMGCR cDNA did not. These results suggest that the three HMGCR-related muscle diseases share disease mechanisms related to skeletal muscle development.

2.
Mov Disord ; 2024 Apr 15.
Article in English | MEDLINE | ID: mdl-38619077

ABSTRACT

Status dystonicus is the most severe form of dystonia with life-threatening complications if not treated promptly. We present consensus recommendations for the initial management of acutely worsening dystonia (including pre-status dystonicus and status dystonicus), as well as refractory status dystonicus in children. This guideline provides a stepwise approach to assessment, triage, interdisciplinary treatment, and monitoring of status dystonicus. The clinical pathways aim to: (1) facilitate timely recognition/triage of worsening dystonia, (2) standardize supportive and dystonia-directed therapies, (3) provide structure for interdisciplinary cooperation, (4) integrate advances in genomics and neuromodulation, (5) enable multicenter quality improvement and research, and (6) improve outcomes. © 2024 International Parkinson and Movement Disorder Society.

3.
Am J Hum Genet ; 110(6): 989-997, 2023 06 01.
Article in English | MEDLINE | ID: mdl-37167966

ABSTRACT

Statins are a mainstay intervention for cardiovascular disease prevention, yet their use can cause rare severe myopathy. HMG-CoA reductase, an essential enzyme in the mevalonate pathway, is the target of statins. We identified nine individuals from five unrelated families with unexplained limb-girdle like muscular dystrophy and bi-allelic variants in HMGCR via clinical and research exome sequencing. The clinical features resembled other genetic causes of muscular dystrophy with incidental high CPK levels (>1,000 U/L), proximal muscle weakness, variable age of onset, and progression leading to impaired ambulation. Muscle biopsies in most affected individuals showed non-specific dystrophic changes with non-diagnostic immunohistochemistry. Molecular modeling analyses revealed variants to be destabilizing and affecting protein oligomerization. Protein activity studies using three variants (p.Asp623Asn, p.Tyr792Cys, and p.Arg443Gln) identified in affected individuals confirmed decreased enzymatic activity and reduced protein stability. In summary, we showed that individuals with bi-allelic amorphic (i.e., null and/or hypomorphic) variants in HMGCR display phenotypes that resemble non-genetic causes of myopathy involving this reductase. This study expands our knowledge regarding the mechanisms leading to muscular dystrophy through dysregulation of the mevalonate pathway, autoimmune myopathy, and statin-induced myopathy.


Subject(s)
Hydroxymethylglutaryl-CoA Reductase Inhibitors , Muscular Diseases , Muscular Dystrophies, Limb-Girdle , Muscular Dystrophies , Humans , Hydroxymethylglutaryl-CoA Reductase Inhibitors/therapeutic use , Mevalonic Acid , Muscular Dystrophies, Limb-Girdle/genetics , Muscular Dystrophies, Limb-Girdle/diagnosis , Muscular Diseases/genetics , Oxidoreductases , Hydroxymethylglutaryl CoA Reductases/genetics , Hydroxymethylglutaryl CoA Reductases/adverse effects
4.
Adv Genet (Hoboken) ; 4(1): 2200013, 2023 Mar.
Article in English | MEDLINE | ID: mdl-36910591

ABSTRACT

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic pain disorder causing symptoms of urinary frequency, urgency, and bladder discomfort or pain. Although this condition affects a large population, little is known about its etiology. Genetic analyses of whole exome sequencing are performed on 109 individuals with IC/BPS. One family has a previously reported SIX5 variant (ENST00000317578.6:c.472G>A, p.Ala158Thr), consistent with Branchiootorenal syndrome 2 (BOR2). A likely pathogenic heterozygous variant in ATP2A2 (ENST00000539276.2:c.235G>A, p.Glu79Lys) is identified in two unrelated probands, indicating possible Darier-White disease. Two private heterozygous variants are identified in ATP2C1 (ENST00000393221.4:c.2358A>T, p.Glu786Asp (VUS/Likely Pathogenic) and ENST00000393221.4:c.989C>G, p.Thr330Ser (likely pathogenic)), indicative of Hailey-Hailey Disease. Sequence kernel association test analysis finds an increased burden of rare ATP2C1 variants in the IC/BPS cases versus a control cohort (p = 0.03, OR = 6.76), though does not survive Bonferroni correction. The data suggest that some individuals with IC/BPS may have unrecognized Mendelian syndromes. Comprehensive phenotyping and genotyping aid in understanding the range of diagnoses in the population-based IC/BPS cohort. Conversely, ATP2C1, ATP2A2, and SIX5 may be candidate genes for IC/BPS. Further evaluation with larger numbers is needed. Genetically screening individuals with IC/BPS may help diagnose and treat this painful disorder due to its heterogeneous nature.

5.
Acta Neuropathol ; 145(4): 479-496, 2023 04.
Article in English | MEDLINE | ID: mdl-36799992

ABSTRACT

DTNA encodes α-dystrobrevin, a component of the macromolecular dystrophin-glycoprotein complex (DGC) that binds to dystrophin/utrophin and α-syntrophin. Mice lacking α-dystrobrevin have a muscular dystrophy phenotype, but variants in DTNA have not previously been associated with human skeletal muscle disease. We present 12 individuals from four unrelated families with two different monoallelic DTNA variants affecting the coiled-coil domain of α-dystrobrevin. The five affected individuals from family A harbor a c.1585G > A; p.Glu529Lys variant, while the recurrent c.1567_1587del; p.Gln523_Glu529del DTNA variant was identified in the other three families (family B: four affected individuals, family C: one affected individual, and family D: two affected individuals). Myalgia and exercise intolerance, with variable ages of onset, were reported in 10 of 12 affected individuals. Proximal lower limb weakness with onset in the first decade of life was noted in three individuals. Persistent elevations of serum creatine kinase (CK) levels were detected in 11 of 12 affected individuals, 1 of whom had an episode of rhabdomyolysis at 20 years of age. Autism spectrum disorder or learning disabilities were reported in four individuals with the c.1567_1587 deletion. Muscle biopsies in eight affected individuals showed mixed myopathic and dystrophic findings, characterized by fiber size variability, internalized nuclei, and slightly increased extracellular connective tissue and inflammation. Immunofluorescence analysis of biopsies from five affected individuals showed reduced α-dystrobrevin immunoreactivity and variably reduced immunoreactivity of other DGC proteins: dystrophin, α, ß, δ and γ-sarcoglycans, and α and ß-dystroglycans. The DTNA deletion disrupted an interaction between α-dystrobrevin and syntrophin. Specific variants in the coiled-coil domain of DTNA cause skeletal muscle disease with variable penetrance. Affected individuals show a spectrum of clinical manifestations, with severity ranging from hyperCKemia, myalgias, and exercise intolerance to childhood-onset proximal muscle weakness. Our findings expand the molecular etiologies of both muscular dystrophy and paucisymptomatic hyperCKemia, to now include monoallelic DTNA variants as a novel cause of skeletal muscle disease in humans.


Subject(s)
Autism Spectrum Disorder , Muscular Dystrophies , Neuropeptides , Mice , Humans , Animals , Child , Dystrophin/genetics , Dystrophin/metabolism , Autism Spectrum Disorder/metabolism , Muscular Dystrophies/metabolism , Dystroglycans/metabolism , Alternative Splicing , Muscle, Skeletal/pathology , Neuropeptides/genetics , Neuropeptides/metabolism , Dystrophin-Associated Proteins/genetics , Dystrophin-Associated Proteins/metabolism
6.
Am J Med Genet A ; 188(12): 3531-3534, 2022 12.
Article in English | MEDLINE | ID: mdl-35975723

ABSTRACT

Bi-allelic loss-of-function variants in Von Willebrand factor type A (VWA1) were recently discovered to lead to an early onset motor neuropathy or neuromyopathy. What makes this discovery particularly notable is the high frequency of one of the VWA1 (NM_022834.5) founder variants, c.62_71dup (p.Gly25ArgfsTer74), which nears 0.01% in European populations, and suggests that there may be a wide spectrum of disease features and severity. Here, we report two cases from nonconsanguineous families in North America that presented in early childhood with lower extremity weakness and prominent foot deformities, and were found to carry bi-allelic variants in VWA1. We draw focus to upper motor neuron signs and abnormal gait phenotypes as presenting symptoms in VWA1-related disorder and expand the clinical and molecular spectrum.


Subject(s)
Loss of Heterozygosity , Motor Neurons , Child, Preschool , Humans , Alleles , Phenotype , Gait/genetics , Extracellular Matrix Proteins
7.
Ann Clin Transl Neurol ; 9(8): 1302-1309, 2022 08.
Article in English | MEDLINE | ID: mdl-35734998

ABSTRACT

Many individuals with muscular dystrophies remain genetically undiagnosed despite clinical diagnostic testing, including exome sequencing. Some may harbor previously undetected structural variants (SVs) or cryptic splice sites. We enrolled 10 unrelated families: nine had muscular dystrophy but lacked complete genetic diagnoses and one had an asymptomatic DMD duplication. Nanopore genomic long-read sequencing identified previously undetected pathogenic variants in four individuals: an SV in DMD, an SV in LAMA2, and two single nucleotide variants in DMD that alter splicing. The DMD duplication in the asymptomatic individual was in tandem. Nanopore sequencing may help streamline genetic diagnostic approaches for muscular dystrophy.


Subject(s)
Muscular Dystrophy, Duchenne , Nanopore Sequencing , Nanopores , Humans , Muscular Dystrophy, Duchenne/diagnosis , Muscular Dystrophy, Duchenne/genetics , Exome Sequencing
8.
J Genet Couns ; 31(3): 803-814, 2022 06.
Article in English | MEDLINE | ID: mdl-35037741

ABSTRACT

Spinal muscular atrophy (SMA) is an autosomal recessive genetic disease characterized by muscle weakness and atrophy with usually typical cognition. The first disease-modifying therapy for SMA, nusinersen, was approved by the United States Food and Drug Administration (FDA) in 2016 and leads to improved outcomes, especially when administered presymptomatically. Population-wide carrier screening and newborn screening (NBS) are now recommended by several professional organizations to promote reproductive autonomy, early diagnosis, and treatment. Prenatal genetic counselors (GCs) are important providers of the SMA screening and diagnosis process, but the possible impact of nusinersen on their practice has not been explored. A survey of 182 prenatal GCs in the United States (US) assessed baseline knowledge of nusinersen and likelihood of discussing this option with prospective parents. The majority of GCs (94.5%) were aware of this drug, and almost all (87.3%) felt that this information would affect pregnancy management decisions. However, less than half of GCs (49.2%) felt confident discussing nusinersen, 45.1% were unaware if this treatment was available in their practice setting, and one in five (19.3%) did not know where to find information about SMA treatments. Participants were more confident and knowledgeable about NBS for SMA, and several indicated that NBS would reduce their emphasis on carrier screening and diagnostic testing, not recognizing that an early prenatal diagnosis can enable preparations for complex, time-sensitive treatment. Only 5.0% of participants felt that a prenatal GC should discuss nusinersen with prospective parents. However, encouragingly, nearly all GCs who felt confident discussing this treatment option (86.4%) reported using this information weekly in their real-world practice. These data highlight an opportunity to provide up-to-date education about SMA treatments, as well as the significant impacts of early diagnosis. Additionally, interdisciplinary communication and care may be appropriate to clarify healthcare resources available and support a variety of patient needs. Increasing awareness and confidence about available options can help prenatal GCs empower patient autonomy and shared decision-making in the new era of disease-modifying treatment for SMA.


Subject(s)
Genetic Counseling , Muscular Atrophy, Spinal , Female , Humans , Infant, Newborn , Muscular Atrophy, Spinal/diagnosis , Muscular Atrophy, Spinal/genetics , Muscular Atrophy, Spinal/therapy , Neonatal Screening , Pregnancy , Prenatal Diagnosis , Prospective Studies
9.
Int J Neonatal Screen ; 7(2)2021 May 23.
Article in English | MEDLINE | ID: mdl-34071063

ABSTRACT

Massachusetts began newborn screening (NBS) for Spinal Muscular Atrophy (SMA) following the availability of new treatment options. The New England Newborn Screening Program developed, validated, and implemented a screening algorithm for the detection of SMA-affected infants who show absent SMN1 Exon 7 by Real-Time™ quantitative PCR (qPCR). We screened 179,467 neonates and identified 9 SMA-affected infants, all of whom were referred to a specialist by day of life 6 (average and median 4 days of life). Another ten SMN1 hybrids were observed but never referred. The nine referred infants who were confirmed to have SMA were entered into treatment protocols. Early data show that some SMA-affected children have remained asymptomatic and are meeting developmental milestones and some have mild to moderate delays. The Massachusetts experience demonstrates that SMA NBS is feasible, can be implemented on a population basis, and helps engage infants for early treatment to maximize benefit.

10.
Nat Commun ; 12(1): 1135, 2021 02 18.
Article in English | MEDLINE | ID: mdl-33602924

ABSTRACT

While >300 disease-causing variants have been identified in the mitochondrial DNA (mtDNA) polymerase γ, no mitochondrial phenotypes have been associated with POLRMT, the RNA polymerase responsible for transcription of the mitochondrial genome. Here, we characterise the clinical and molecular nature of POLRMT variants in eight individuals from seven unrelated families. Patients present with global developmental delay, hypotonia, short stature, and speech/intellectual disability in childhood; one subject displayed an indolent progressive external ophthalmoplegia phenotype. Massive parallel sequencing of all subjects identifies recessive and dominant variants in the POLRMT gene. Patient fibroblasts have a defect in mitochondrial mRNA synthesis, but no mtDNA deletions or copy number abnormalities. The in vitro characterisation of the recombinant POLRMT mutants reveals variable, but deleterious effects on mitochondrial transcription. Together, our in vivo and in vitro functional studies of POLRMT variants establish defective mitochondrial transcription as an important disease mechanism.


Subject(s)
DNA-Directed RNA Polymerases/genetics , Mitochondria/genetics , Mutation/genetics , Nervous System Diseases/genetics , Transcription, Genetic , Adolescent , Adult , Child , DNA, Mitochondrial/genetics , DNA-Directed RNA Polymerases/chemistry , Female , Fibroblasts/metabolism , Fibroblasts/pathology , Humans , Infant , Male , Nervous System Diseases/pathology , Oxidative Phosphorylation , Pedigree , Protein Domains , Protein Subunits/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Young Adult
12.
Neurol Genet ; 5(2): e312, 2019 Apr.
Article in English | MEDLINE | ID: mdl-31041394

ABSTRACT

OBJECTIVE: To identify the genetic cause of disease in a form of congenital spinal muscular atrophy and arthrogryposis (CSMAA). METHODS: A 2-year-old boy was diagnosed with arthrogryposis multiplex congenita, severe skeletal abnormalities, torticollis, vocal cord paralysis, and diminished lower limb movement. Whole-exome sequencing (WES) was performed on the proband and family members. In silico modeling of protein structure and heterologous protein expression and cytotoxicity assays were performed to validate pathogenicity of the identified variant. RESULTS: WES revealed a homozygous mutation in the TRPV4 gene (c.281C>T; p.S94L). The identification of a recessive mutation in TRPV4 extends the spectrum of mutations in recessive forms of the TRPV4-associated disease. p.S94L and other previously identified TRPV4 variants in different protein domains were compared in structural modeling and functional studies. In silico structural modeling suggests that the p.S94L mutation is in the disordered N-terminal region proximal to important regulatory binding sites for phosphoinositides and for PACSIN3, which could lead to alterations in trafficking and/or channel sensitivity. Functional studies by Western blot and immunohistochemical analysis show that p.S94L increased TRPV4 activity-based cytotoxicity and resultant decreased TRPV4 expression levels, therefore involves a gain-of-function mechanism. CONCLUSIONS: This study identifies a novel homozygous mutation in TRPV4 as a cause of the recessive form of CSMAA.

13.
Mol Genet Genomic Med ; 7(3): e552, 2019 03.
Article in English | MEDLINE | ID: mdl-30688039

ABSTRACT

BACKGROUND: Pathogenic mutations causing aberrant splicing are often difficult to detect. Standard variant analysis of next-generation sequence (NGS) data focuses on canonical splice sites. Noncanonical splice sites are more difficult to ascertain. METHODS: We developed a bioinformatics pipeline that screens existing NGS data for potentially aberrant novel essential splice sites (PANESS) and performed a pilot study on a family with a myotonic disorder. Further analyses were performed via qRT-PCR, immunoblotting, and immunohistochemistry. RNAi knockdown studies were performed in Drosophila to model the gene deficiency. RESULTS: The PANESS pipeline identified a homozygous ATP2A1 variant (NC_000016.9:g.28905928G>A; NM_004320.4:c.1287G>A:p.(Glu429=)) that was predicted to cause the omission of exon 11. Aberrant splicing of ATP2A1 was confirmed via qRT-PCR, and abnormal expression of the protein product sarcoplasmic/endoplasmic reticulum Ca++ ATPase 1 (SERCA1) was demonstrated in quadriceps femoris tissue from the proband. Ubiquitous knockdown of SERCA led to lethality in Drosophila, as did knockdown targeting differentiating or fusing myoblasts. CONCLUSIONS: This study confirms the potential of novel in silico algorithms to detect cryptic mutations in existing NGS data; expands the phenotypic spectrum of ATP2A1 mutations beyond classic Brody myopathy; and suggests that genetic testing of ATP2A1 should be considered in patients with clinical myotonia.


Subject(s)
Computational Biology/methods , Exome Sequencing/methods , Genetic Testing/methods , Myotonia Congenita/genetics , RNA Splice Sites/genetics , Sarcoplasmic Reticulum Calcium-Transporting ATPases/genetics , Algorithms , Animals , Cells, Cultured , Drosophila melanogaster , Humans , Male , Muscle, Skeletal/metabolism , Mutation , Myotonia Congenita/pathology , Phenotype , Sarcoplasmic Reticulum Calcium-Transporting ATPases/metabolism , Young Adult
14.
Physiol Genomics ; 50(11): 929-939, 2018 11 01.
Article in English | MEDLINE | ID: mdl-30345904

ABSTRACT

Next-generation sequencing is commonly used to screen for pathogenic mutations in families with Mendelian disorders, but due to the pace of discoveries, gaps have widened for some diseases between genetic and pathophysiological knowledge. We recruited and analyzed 16 families with limb-girdle muscular dystrophy (LGMD) of Arab descent from Saudi Arabia and Sudan who did not have confirmed genetic diagnoses. The analysis included both traditional and next-generation sequencing approaches. Cellular and metabolic studies were performed on Pyroxd1 siRNA C2C12 myoblasts and controls. Pathogenic mutations were identified in eight of the 16 families. One Sudanese family of Arab descent residing in Saudi Arabia harbored a homozygous c.464A>G, p.Asn155Ser mutation in PYROXD1, a gene recently reported in association with myofibrillar myopathy and whose protein product reduces thiol residues. Pyroxd1 deficiency in murine C2C12 myoblasts yielded evidence for impairments of cellular proliferation, migration, and differentiation, while CG10721 (Pyroxd1 fly homolog) knockdown in Drosophila yielded a lethal phenotype. Further investigations indicated that Pyroxd1 does not localize to mitochondria, yet Pyroxd1 deficiency is associated with decreased cellular respiration. This study identified pathogenic mutations in half of the LGMD families from the cohort, including one in PYROXD1. Developmental impairments were demonstrated in vitro for Pyroxd1 deficiency and in vivo for CG10721 deficiency, with reduced metabolic activity in vitro for Pyroxd1 deficiency.


Subject(s)
Muscular Dystrophies, Limb-Girdle/genetics , Mutation , Oxidoreductases Acting on Sulfur Group Donors/genetics , Adult , Animals , Animals, Genetically Modified , Cell Respiration/genetics , Cells, Cultured , Drosophila , Drosophila Proteins/genetics , Female , Humans , Male , Mice , Mitochondria, Muscle/genetics , Mitochondria, Muscle/metabolism , Mitochondria, Muscle/pathology , Muscular Dystrophies, Limb-Girdle/pathology , Myoblasts/pathology , Pedigree , Saudi Arabia , Sudan
15.
Sci Transl Med ; 9(386)2017 04 19.
Article in English | MEDLINE | ID: mdl-28424332

ABSTRACT

Exome and whole-genome sequencing are becoming increasingly routine approaches in Mendelian disease diagnosis. Despite their success, the current diagnostic rate for genomic analyses across a variety of rare diseases is approximately 25 to 50%. We explore the utility of transcriptome sequencing [RNA sequencing (RNA-seq)] as a complementary diagnostic tool in a cohort of 50 patients with genetically undiagnosed rare muscle disorders. We describe an integrated approach to analyze patient muscle RNA-seq, leveraging an analysis framework focused on the detection of transcript-level changes that are unique to the patient compared to more than 180 control skeletal muscle samples. We demonstrate the power of RNA-seq to validate candidate splice-disrupting mutations and to identify splice-altering variants in both exonic and deep intronic regions, yielding an overall diagnosis rate of 35%. We also report the discovery of a highly recurrent de novo intronic mutation in COL6A1 that results in a dominantly acting splice-gain event, disrupting the critical glycine repeat motif of the triple helical domain. We identify this pathogenic variant in a total of 27 genetically unsolved patients in an external collagen VI-like dystrophy cohort, thus explaining approximately 25% of patients clinically suggestive of having collagen VI dystrophy in whom prior genetic analysis is negative. Overall, this study represents a large systematic application of transcriptome sequencing to rare disease diagnosis and highlights its utility for the detection and interpretation of variants missed by current standard diagnostic approaches.


Subject(s)
High-Throughput Nucleotide Sequencing/methods , Transcriptome/genetics , Collagen Type VI/genetics , Collagen Type VI/metabolism , Humans , Muscular Diseases/genetics , Muscular Diseases/metabolism , Mutation
16.
J Hum Genet ; 62(2): 243-252, 2017 Feb.
Article in English | MEDLINE | ID: mdl-27708273

ABSTRACT

The current study characterizes a cohort of limb-girdle muscular dystrophy (LGMD) in the United States using whole-exome sequencing. Fifty-five families affected by LGMD were recruited using an institutionally approved protocol. Exome sequencing was performed on probands and selected parental samples. Pathogenic mutations and cosegregation patterns were confirmed by Sanger sequencing. Twenty-two families (40%) had novel and previously reported pathogenic mutations, primarily in LGMD genes, and also in genes for Duchenne muscular dystrophy, facioscapulohumeral muscular dystrophy, congenital myopathy, myofibrillar myopathy, inclusion body myopathy and Pompe disease. One family was diagnosed via clinical testing. Dominant mutations were identified in COL6A1, COL6A3, FLNC, LMNA, RYR1, SMCHD1 and VCP, recessive mutations in ANO5, CAPN3, GAA, LAMA2, SGCA and SGCG, and X-linked mutations in DMD. A previously reported variant in DMD was confirmed to be benign. Exome sequencing is a powerful diagnostic tool for LGMD. Despite careful phenotypic screening, pathogenic mutations were found in other muscle disease genes, largely accounting for the increased sensitivity of exome sequencing. Our experience suggests that broad sequencing panels are useful for these analyses because of the phenotypic overlap of many neuromuscular conditions. The confirmation of a benign DMD variant illustrates the potential of exome sequencing to help determine pathogenicity.


Subject(s)
Exome/genetics , Genetic Testing/methods , Muscular Dystrophies, Limb-Girdle/diagnosis , Muscular Dystrophies, Limb-Girdle/genetics , Base Sequence , Distal Myopathies/diagnosis , Distal Myopathies/genetics , Female , Glycogen Storage Disease Type II/diagnosis , Glycogen Storage Disease Type II/genetics , Humans , Male , Muscular Dystrophy, Duchenne/diagnosis , Muscular Dystrophy, Duchenne/genetics , Muscular Dystrophy, Facioscapulohumeral/diagnosis , Muscular Dystrophy, Facioscapulohumeral/genetics , Mutation/genetics , Myopathies, Structural, Congenital/diagnosis , Myopathies, Structural, Congenital/genetics , Sequence Analysis, DNA/methods , United States
17.
Cell Stem Cell ; 19(6): 800-807, 2016 12 01.
Article in English | MEDLINE | ID: mdl-27641304

ABSTRACT

Cell-surface markers for prospective isolation of stem cells from human skeletal muscle have been difficult to identify. Such markers would be powerful tools for studying satellite cell function during homeostasis and in pathogenesis of diseases such as muscular dystrophies. In this study, we show that the tetraspanin KAI/CD82 is an excellent marker for prospectively isolating stem cells from human fetal and adult skeletal muscle. Human CD82+ muscle cells robustly engraft into a mouse model of muscular dystrophy. shRNA knockdown of CD82 in myogenic cells reduces myoblast proliferation, suggesting it is functionally involved in muscle homeostasis. CD82 physically interacts with alpha7beta1 integrin (α7ß1-ITG) and with α-sarcoglycan, a member of the Dystrophin-Associated Glycoprotein Complex (DAPC), both of which have been linked to muscular dystrophies. Consistently, CD82 expression is decreased in Duchenne muscular dystrophy patients. Together, these findings suggest that CD82 function may be important for muscle stem cell function in muscular disorders.


Subject(s)
Cell Separation/methods , Kangai-1 Protein/metabolism , Muscular Dystrophies/metabolism , Muscular Dystrophies/pathology , Satellite Cells, Skeletal Muscle/metabolism , Adult , Animals , Antigens, CD/metabolism , Biomarkers/metabolism , CD146 Antigen/metabolism , HEK293 Cells , Humans , Immunoprecipitation , Integrin alpha Chains/metabolism , Mice, SCID , Muscular Dystrophy, Animal/pathology , Sarcoglycans/metabolism
18.
Muscle Nerve ; 54(4): 690-5, 2016 10.
Article in English | MEDLINE | ID: mdl-26934379

ABSTRACT

INTRODUCTION: The genetic causes of limb-girdle muscular dystrophy (LGMD) have been studied in numerous countries, but such investigations have been limited in Egypt. METHODS: A cohort of 30 families with suspected LGMD from Assiut, Egypt, was studied using immunohistochemistry, homozygosity mapping, Sanger sequencing, and whole exome sequencing. RESULTS: Six families were confirmed to have pathogenic mutations, 4 in SGCA and 2 in DMD. Of these, 3 families harbored a single nonsense mutation in SGCA, suggesting that this may be a common mutation in Assiut, Egypt, originating from a founder effect. CONCLUSIONS: The Assiut region in Egypt appears to share at least several of the common LGMD genes found in other parts of the world. It is notable that 4 of the 6 mutations were ascertained by means of whole exome sequencing, even though it was the last approach adopted. This illustrates the power of this technique for identifying causative mutations for muscular dystrophies. Muscle Nerve 54: 690-695, 2016.


Subject(s)
Codon, Nonsense/genetics , Homozygote , Muscular Dystrophies, Limb-Girdle/epidemiology , Muscular Dystrophies, Limb-Girdle/genetics , Sarcoglycans/genetics , Egypt/epidemiology , Female , Humans , Male , Muscular Dystrophies, Limb-Girdle/diagnosis , Pedigree
19.
Am J Hum Genet ; 96(4): 612-22, 2015 Apr 02.
Article in English | MEDLINE | ID: mdl-25817016

ABSTRACT

Robinow syndrome is a genetically heterogeneous disorder characterized by mesomelic limb shortening, genital hypoplasia, and distinctive facial features and for which both autosomal-recessive and autosomal-dominant inheritance patterns have been described. Causative variants in the non-canonical signaling gene WNT5A underlie a subset of autosomal-dominant Robinow syndrome (DRS) cases, but most individuals with DRS remain without a molecular diagnosis. We performed whole-exome sequencing in four unrelated DRS-affected individuals without coding mutations in WNT5A and found heterozygous DVL1 exon 14 mutations in three of them. Targeted Sanger sequencing in additional subjects with DRS uncovered DVL1 exon 14 mutations in five individuals, including a pair of monozygotic twins. In total, six distinct frameshift mutations were found in eight subjects, and all were heterozygous truncating variants within the penultimate exon of DVL1. In five families in which samples from unaffected parents were available, the variants were demonstrated to represent de novo mutations. All variant alleles are predicted to result in a premature termination codon within the last exon, escape nonsense-mediated decay (NMD), and most likely generate a C-terminally truncated protein with a distinct -1 reading-frame terminus. Study of the transcripts extracted from affected subjects' leukocytes confirmed expression of both wild-type and variant alleles, supporting the hypothesis that mutant mRNA escapes NMD. Genomic variants identified in our study suggest that truncation of the C-terminal domain of DVL1, a protein hypothesized to have a downstream role in the Wnt-5a non-canonical pathway, is a common cause of DRS.


Subject(s)
Adaptor Proteins, Signal Transducing/genetics , Craniofacial Abnormalities/genetics , Dwarfism/genetics , Frameshift Mutation/genetics , Limb Deformities, Congenital/genetics , Phosphoproteins/genetics , Urogenital Abnormalities/genetics , Amino Acid Sequence , Base Sequence , DNA Primers/genetics , Dishevelled Proteins , Exome/genetics , Exons/genetics , Gene Components , Humans , Molecular Sequence Data , Sequence Analysis, DNA
20.
J Genet Couns ; 24(2): 325-35, 2015 Apr.
Article in English | MEDLINE | ID: mdl-25277096

ABSTRACT

The pediatric diagnostic odyssey is a period of uncertainty and emotional turmoil for families, often characterized by multiple minor medical procedures (such as venipuncture) that children may find distressing. Interventions to reduce distress are rarely offered, despite evidence that this is crucial both for avoiding anticipatory anxiety before future procedures and for improving healthcare compliance in adulthood. We interviewed ten mothers of children with neuromuscular disorders, asking about their perceptions of their child's experiences with different medical procedures, the emotional impact of the diagnostic odyssey, implications of obtaining a diagnosis, and interactions with healthcare providers. We coded interviews in ATLAS.ti (version 7.0) based on a priori and emergent themes, and analyzed them based on the principles of interpretive description. We found that predicting and assessing children's reactions to procedures is challenging; parents reported non-invasive procedures such as x-rays were distressing for some children, and that providers did not detect subtle indicators of distress. Parents valued obtaining a diagnosis because it validated their concerns, enabled planning for the child's future healthcare needs, and allowed access to established support networks. This study suggests that healthcare providers can improve the experience of the diagnostic odyssey by validating family concerns and connecting them to support services that are available without a diagnosis.


Subject(s)
Genetic Counseling/psychology , Mothers/psychology , Neuromuscular Diseases/diagnosis , Stress, Psychological/psychology , Adolescent , Adult , Child , Child, Preschool , Emotions , Female , Humans , Male , Neuromuscular Diseases/diagnostic imaging , Neuromuscular Diseases/genetics , Perception , Radiography
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