ABSTRACT
INTRODUCTION: Progressive bulbar motor neuropathy is primarily caused by bulbar-onset ALS. Hereditary amyloidosis type IV also presents with a bulbar neuropathy that mimics motor neuron disease. The disease is prevalent in Finland only and is not commonly included in the differential diagnosis of ALS. METHODS: We studied 18 members of a family in which some had bulbar motor neuropathy, and we performed exome sequencing. RESULTS: Five affected family members were found to have a D187Y substitution in the GSN gene known to cause hereditary amyloidosis type IV. CONCLUSIONS: This American family presented with progressive bulbar neuropathy due to a gelsolin mutation not found in Finland. Hereditary amyloidosis type IV presents with bulbar motor neuropathy and not with peripheral neuropathy as occurs with common forms of amyloidosis. This report demonstrates the power of exome sequencing to determine the cause of rare hereditary diseases with incomplete or atypical phenotypes. Muscle Nerve 56: 1001-1005, 2017.
Subject(s)
Amyloidosis, Familial/genetics , Bulbar Palsy, Progressive/genetics , Family Health , Gelsolin/genetics , Mutation/genetics , Aged, 80 and over , Amyloidosis, Familial/complications , Bulbar Palsy, Progressive/complications , DNA Mutational Analysis , Female , Humans , Middle AgedABSTRACT
BACKGROUND: The autosomal dominant spinocerebellar ataxias are most commonly caused by nucleotide repeat expansions followed by base-pair changes in functionally important genes. Structural variation has recently been shown to underlie spinocerebellar ataxia types 15 and 20. METHODS: We applied single-nucleotide polymorphism (SNP) genotyping to determine whether structural variation causes spinocerebellar ataxia in a family from France. RESULTS: We identified an approximately 7.5-megabasepair duplication on chromosome 11q21-11q22.3 that segregates with disease. This duplication contains an estimated 44 genes. Duplications at this locus were not found in control individuals. CONCLUSIONS: We have identified a new spastic ataxia syndrome caused by a genomic duplication, which we have denoted as spinocerebellar ataxia type 39. Finding additional families with this phenotype will be important to identify the genetic lesion underlying disease.
Subject(s)
Genetic Linkage , Genetic Predisposition to Disease , Intellectual Disability/genetics , Muscle Spasticity/genetics , Optic Atrophy/genetics , Spinocerebellar Ataxias/genetics , Trisomy , Chromosome Mapping , Chromosomes, Human, Pair 11 , France , Genotype , Humans , Male , Middle Aged , Pedigree , Phenotype , Polymorphism, Single Nucleotide/geneticsABSTRACT
We report here the genetic basis for a form of progressive hereditary spastic paraplegia (SPG43) previously described in two Malian sisters. Exome sequencing revealed a homozygous missense variant (c.187G>C; p.Ala63Pro) in C19orf12, a gene recently implicated in neurodegeneration with brain iron accumulation (NBIA). The same mutation was subsequently also found in a Brazilian family with features of NBIA, and we identified another NBIA patient with a three-nucleotide deletion (c.197_199del; p.Gly66del). Haplotype analysis revealed that the p.Ala63Pro mutations have a common origin, but MRI scans showed no brain iron deposition in the Malian SPG43 subjects. Heterologous expression of these SPG43 and NBIA variants resulted in similar alterations in the subcellular distribution of C19orf12. The SPG43 and NBIA variants reported here as well as the most common C19orf12 missense mutation reported in NBIA patients are found within a highly conserved, extended hydrophobic domain in C19orf12, underscoring the functional importance of this domain.
Subject(s)
Mitochondrial Proteins/genetics , Mutation , Spastic Paraplegia, Hereditary/diagnosis , Spastic Paraplegia, Hereditary/genetics , Adolescent , Amino Acid Sequence , Brain/metabolism , Brain/pathology , Homozygote , Humans , Intracellular Space/metabolism , Magnetic Resonance Imaging , Male , Mitochondrial Proteins/chemistry , Mitochondrial Proteins/metabolism , Molecular Sequence Data , Protein Transport , Sequence Alignment , Sequence Deletion , Spastic Paraplegia, Hereditary/metabolismABSTRACT
Brown-Vialetto-Van Laere syndrome was first described in 1894 as a rare neurodegenerative disorder characterized by progressive sensorineural deafness in combination with childhood amyotrophic lateral sclerosis. Mutations in the gene, SLC52A3 (formerly C20orf54), one of three known riboflavin transporter genes, have recently been shown to underlie a number of severe cases of Brown-Vialetto-Van Laere syndrome; however, cases and families with this disease exist that do not appear to be caused by SLC52A3 mutations. We used a combination of linkage and exome sequencing to identify the disease causing mutation in an extended Lebanese Brown-Vialetto-Van Laere kindred, whose affected members were negative for SLC52A3 mutations. We identified a novel mutation in a second member of the riboflavin transporter gene family (gene symbol: SLC52A2) as the cause of disease in this family. The same mutation was identified in one additional subject, from 44 screened. Within this group of 44 patients, we also identified two additional cases with SLC52A3 mutations, but none with mutations in the remaining member of this gene family, SLC52A1. We believe this strongly supports the notion that defective riboflavin transport plays an important role in Brown-Vialetto-Van Laere syndrome. Initial work has indicated that patients with SLC52A3 defects respond to riboflavin treatment clinically and biochemically. Clearly, this makes an excellent candidate therapy for the SLC52A2 mutation-positive patients identified here. Initial riboflavin treatment of one of these patients shows promising results.
Subject(s)
Bulbar Palsy, Progressive/genetics , Exome , Hearing Loss, Sensorineural/genetics , Motor Neuron Disease/genetics , Mutation , Receptors, G-Protein-Coupled/genetics , Alleles , Child , Child, Preschool , Female , Gene Frequency , Genotype , Humans , Male , Pedigree , Polymorphism, Single NucleotideABSTRACT
It was recently reported that rs1541160 on chromosome 1q24.2 has a marked effect on survival of amyotrophic lateral sclerosis (ALS) patients by influencing KIFAP3 expression. The cohorts used in that study were collected from ALS specialty clinics. We attempted to replicate these findings in a population-based cohort of 504 Italian ALS patients. None of 140 SNPs genotyped within the KIFAP3 locus (including rs1541160) had an effect on survival (log-rank P value for rs1541160 = 0.47) or on gene expression in that region. These data illustrate the complexities associated with analyzing ALS phenotypes for association.
Subject(s)
Adaptor Proteins, Signal Transducing/genetics , Amyotrophic Lateral Sclerosis/genetics , Cytoskeletal Proteins/genetics , Polymorphism, Single Nucleotide , Adaptor Proteins, Signal Transducing/metabolism , Amyotrophic Lateral Sclerosis/metabolism , Blotting, Western , Brain/metabolism , Brain/pathology , Chromosomes, Human, Pair 1/genetics , Cohort Studies , Cytoskeletal Proteins/metabolism , Gene Expression Profiling/statistics & numerical data , Gene Frequency , Genetic Predisposition to Disease , Genotype , Humans , Italy , Kaplan-Meier Estimate , Phenotype , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
The vacuolar H+-ATPase is a large multi-subunit proton pump, composed of an integral membrane V0 domain, involved in proton translocation, and a peripheral V1 domain, catalysing ATP hydrolysis. This complex is widely distributed on the membrane of various subcellular organelles, such as endosomes and lysosomes, and plays a critical role in cellular processes ranging from autophagy to protein trafficking and endocytosis. Variants in ATP6V0A1, the brain-enriched isoform in the V0 domain, have been recently associated with developmental delay and epilepsy in four individuals. Here, we identified 17 individuals from 14 unrelated families with both with new and previously characterized variants in this gene, representing the largest cohort to date. Five affected subjects with biallelic variants in this gene presented with a phenotype of early-onset progressive myoclonus epilepsy with ataxia, while 12 individuals carried de novo missense variants and showed severe developmental and epileptic encephalopathy. The R740Q mutation, which alone accounts for almost 50% of the mutations identified among our cases, leads to failure of lysosomal hydrolysis by directly impairing acidification of the endolysosomal compartment, causing autophagic dysfunction and severe developmental defect in Caenorhabditis elegans. Altogether, our findings further expand the neurological phenotype associated with variants in this gene and provide a direct link with endolysosomal acidification in the pathophysiology of ATP6V0A1-related conditions.
ABSTRACT
Importance: Juvenile amyotrophic lateral sclerosis (ALS) is a rare form of ALS characterized by age of symptom onset less than 25 years and a variable presentation. Objective: To identify the genetic variants associated with juvenile ALS. Design, Setting, and Participants: In this multicenter family-based genetic study, trio whole-exome sequencing was performed to identify the disease-associated gene in a case series of unrelated patients diagnosed with juvenile ALS and severe growth retardation. The patients and their family members were enrolled at academic hospitals and a government research facility between March 1, 2016, and March 13, 2020, and were observed until October 1, 2020. Whole-exome sequencing was also performed in a series of patients with juvenile ALS. A total of 66 patients with juvenile ALS and 6258 adult patients with ALS participated in the study. Patients were selected for the study based on their diagnosis, and all eligible participants were enrolled in the study. None of the participants had a family history of neurological disorders, suggesting de novo variants as the underlying genetic mechanism. Main Outcomes and Measures: De novo variants present only in the index case and not in unaffected family members. Results: Trio whole-exome sequencing was performed in 3 patients diagnosed with juvenile ALS and their parents. An additional 63 patients with juvenile ALS and 6258 adult patients with ALS were subsequently screened for variants in the SPTLC1 gene. De novo variants in SPTLC1 (p.Ala20Ser in 2 patients and p.Ser331Tyr in 1 patient) were identified in 3 unrelated patients diagnosed with juvenile ALS and failure to thrive. A fourth variant (p.Leu39del) was identified in a patient with juvenile ALS where parental DNA was unavailable. Variants in this gene have been previously shown to be associated with autosomal-dominant hereditary sensory autonomic neuropathy, type 1A, by disrupting an essential enzyme complex in the sphingolipid synthesis pathway. Conclusions and Relevance: These data broaden the phenotype associated with SPTLC1 and suggest that patients presenting with juvenile ALS should be screened for variants in this gene.
Subject(s)
Amyotrophic Lateral Sclerosis/genetics , Genetic Predisposition to Disease/genetics , Serine C-Palmitoyltransferase/genetics , Adolescent , Adult , Child , Child, Preschool , Female , Humans , Mutation , Exome Sequencing , Young AdultABSTRACT
Notch signaling is a highly conserved intercellular pathway with tightly regulated and pleiotropic roles in normal tissue development and homeostasis. Dysregulated Notch signaling has also been implicated in human disease, including multiple forms of cancer, and represents an emerging therapeutic target. Successful development of such therapeutics requires a detailed understanding of potential on-target toxicities. Here, we identify autosomal dominant mutations of the canonical Notch ligand Jagged1 (or JAG1) as a cause of peripheral nerve disease in 2 unrelated families with the hereditary axonal neuropathy Charcot-Marie-Tooth disease type 2 (CMT2). Affected individuals in both families exhibited severe vocal fold paresis, a rare feature of peripheral nerve disease that can be life-threatening. Our studies of mutant protein posttranslational modification and localization indicated that the mutations (p.Ser577Arg, p.Ser650Pro) impair protein glycosylation and reduce JAG1 cell surface expression. Mice harboring heterozygous CMT2-associated mutations exhibited mild peripheral neuropathy, and homozygous expression resulted in embryonic lethality by midgestation. Together, our findings highlight a critical role for JAG1 in maintaining peripheral nerve integrity, particularly in the recurrent laryngeal nerve, and provide a basis for the evaluation of peripheral neuropathy as part of the clinical development of Notch pathway-modulating therapeutics.
Subject(s)
Charcot-Marie-Tooth Disease , Genes, Dominant , Jagged-1 Protein , Mutation, Missense , Signal Transduction/genetics , Amino Acid Substitution , Animals , Charcot-Marie-Tooth Disease/genetics , Charcot-Marie-Tooth Disease/metabolism , Female , Glycosylation , Humans , Jagged-1 Protein/genetics , Jagged-1 Protein/metabolism , Male , Mice , Receptors, Notch/genetics , Receptors, Notch/metabolismSubject(s)
Abnormalities, Multiple/genetics , Bulbar Palsy, Progressive/genetics , Membrane Transport Proteins/genetics , Mutation, Missense , Abnormalities, Multiple/pathology , Adolescent , Base Sequence , Bulbar Palsy, Progressive/pathology , Child , Child, Preschool , Fatal Outcome , Female , Heterozygote , Humans , Male , Molecular Sequence Data , Pedigree , Polymorphism, Single Nucleotide/genetics , Respiratory Insufficiency/genetics , Respiratory Insufficiency/pathology , Sequence Analysis, DNA , SyndromeABSTRACT
There are indications that both familial amyotrophic lateral sclerosis (ALS) and sporadic ALS phenotype and prognosis are partly regulated by genetic and environmental factors, supporting the theory that ALS is a multifactorial disease. The aim of this article was to assess the role of ATXN2 intermediate length repeats in a large series of Italian and Sardinian ALS patients and controls carrying a pathogenetic C9ORF72 GGGGCC hexanucleotide repeat. A total of 1972 ALS cases were identified through the database of the Italian ALS Genetic consortium, a collaborative effort including 18 ALS centers throughout Italy. The study population included: (1) 276 Italian and 57 Sardinian ALS cases who carried the C9ORF72 expansion; (2) 1340 Italian and 299 Sardinian ALS cases not carrying the C9ORF72 expansion. A total of healthy 1043 controls were also assessed. Most Italian and Sardinian cases and controls were homozygous for 22/22 or 23/23 repeats or heterozygous for 22/23 repeats of the ATXN2 gene. ATXN2 intermediate length repeats alleles (≥28) were detected in 3 (0.6%) Italian ALS cases carrying the C9ORF72 expansion, in none of the Sardinian ALS cases carrying the expansion, in 60 (4.3%) Italian cases not carrying the expansion, and in 6 (2.0%) Sardinian ALS cases without C9ORF72 expansion. Intermediate length repeat alleles were found in 12 (1.5%) Italian controls and 1 (0.84%) Sardinian controls. Therefore, ALS patients with C9ORF72 expansion showed a lower frequency of ATXN2 polyQ intermediate length repeats than both controls (Italian cases, p = 0.137; Sardinian cases, p = 0.0001) and ALS patients without C9ORF72 expansion (Italian cases, p = 0.005; Sardinian cases, p = 0.178). In our large study on Italian and Sardinian ALS patients with C9ORF72 GGGGCC hexanucleotide repeat expansion, compared to age-, gender- and ethnic-matched controls, ATXN2 polyQ intermediate length does not represent a modifier of ALS risk, differently from non-C9ORF72 mutated patients.
Subject(s)
Amyotrophic Lateral Sclerosis/genetics , Ataxin-2/genetics , DNA Repeat Expansion/genetics , Genetic Association Studies , Proteins/genetics , Aged , C9orf72 Protein , Female , Humans , Italy , Male , Middle AgedABSTRACT
Frontotemporal lobar degeneration is a highly familial disease and the most common known genetic cause is the repeat expansion mutation in the gene C9orf72. We have identified 2 brothers with an expansion mutation in C9orf72 using Southern blotting that is undetectable using repeat-primed polymerase chain reaction. Sequencing using high concentrations of DNA denaturants of a bacterial artificial chromosome clone obtained from one of the brothers identified a 10-base pair deletion adjacent to the expansion that presumably confers strong secondary structure that interferes with the genotyping. Using an alternative method, we have identified missed expansion carriers in our cohort, and this number has increased by approximately 25%. This observation has important implications for patients undergoing genetic testing for C9orf72.
Subject(s)
DNA Repeat Expansion/genetics , Frontotemporal Lobar Degeneration/genetics , Gene Deletion , Heterozygote , Mutation/genetics , Proteins/genetics , Adult , Aged , Aged, 80 and over , C9orf72 Protein , Cohort Studies , Female , Frontotemporal Lobar Degeneration/epidemiology , Genetic Testing/methods , Humans , Male , Middle Aged , Polymerase Chain Reaction/methods , Sequence Analysis, DNA/methods , Young AdultABSTRACT
IMPORTANCE: The family of genes implicated in hereditary spastic paraplegias (HSPs) is quickly expanding, mostly owing to the widespread availability of next-generation DNA sequencing methods. Nevertheless, a genetic diagnosis remains unavailable for many patients. OBJECTIVE: To identify the genetic cause for a novel form of pure autosomal dominant HSP. DESIGN, SETTING, AND PARTICIPANTS: We examined and followed up with a family presenting to a tertiary referral center for evaluation of HSP for a decade until August 2014. Whole-exome sequencing was performed in 4 patients from the same family and was integrated with linkage analysis. Sanger sequencing was used to confirm the presence of the candidate variant in the remaining affected and unaffected members of the family and screen the additional patients with HSP. Five affected and 6 unaffected participants from a 3-generation family with pure adult-onset autosomal dominant HSP of unknown genetic origin were included. Additionally, 163 unrelated participants with pure HSP of unknown genetic cause were screened. MAIN OUTCOME AND MEASURE: Mutation in the neuronal isoform of carnitine palmitoyl-transferase (CPT1C) gene. RESULTS: We identified the nucleotide substitution c.109C>T in exon 3 of CPT1C, which determined the base substitution of an evolutionarily conserved Cys residue for an Arg in the gene product. This variant strictly cosegregated with the disease phenotype and was absent in online single-nucleotide polymorphism databases and in 712 additional exomes of control participants. We showed that CPT1C, which localizes to the endoplasmic reticulum, is expressed in motor neurons and interacts with atlastin-1, an endoplasmic reticulum protein encoded by the ATL1 gene known to be mutated in pure HSPs. The mutation, as indicated by nuclear magnetic resonance spectroscopy studies, alters the protein conformation and reduces the mean (SD) number (213.0 [46.99] vs 81.9 [14.2]; P < .01) and size (0.29 [0.01] vs 0.26 [0.01]; P < .05) of lipid droplets on overexpression in cells. We also observed a reduction of mean (SD) lipid droplets in primary cortical neurons isolated from Cpt1c-/- mice as compared with wild-type mice (1.0 [0.12] vs 0.44 [0.05]; P < .001), suggesting a dominant negative mechanism for the mutation. CONCLUSIONS AND RELEVANCE: This study expands the genetics of autosomal dominant HSP and is the first, to our knowledge, to link mutation in CPT1C with a human disease. The association of the CPT1C mutation with changes in lipid droplet biogenesis supports a role for altered lipid-mediated signal transduction in HSP pathogenesis.
Subject(s)
Carnitine O-Palmitoyltransferase/genetics , Spastic Paraplegia, Hereditary/genetics , Adult , Animals , Humans , Italy , Mice , Mice, Knockout , Middle Aged , Mutation/genetics , PedigreeABSTRACT
Mutations in CHCHD10 have recently been described as a cause of frontotemporal dementia (FTD) comorbid with amyotrophic lateral sclerosis (ALS). The aim of this study was to assess the frequency and clinical characteristics of CHCHD10 mutations in Italian patients diagnosed with familial (n = 64) and apparently sporadic ALS (n = 224). Three apparently sporadic patients were found to carry c.100C>T (p.Pro34Ser) heterozygous variant in the exon 2 of CHCHD10. This mutation had been previously described in 2 unrelated French patients with FTD-ALS. However, our patients had a typical ALS, without evidence of FTD, cerebellar or extrapyramidal signs, or sensorineural deficits. We confirm that CHCHD10 mutations account for â¼ 1% of Italian ALS patients and are a cause of disease in subjects without dementia or other atypical clinical signs.
Subject(s)
Amyotrophic Lateral Sclerosis/genetics , Genetic Association Studies , Genetic Predisposition to Disease/genetics , Mitochondrial Proteins/genetics , Mutation , Aged , Cohort Studies , Female , Frontotemporal Dementia , Humans , Italy , Male , Middle AgedABSTRACT
IMPORTANCE: New genomic strategies can now be applied to identify a diagnosis in patients and families with previously undiagnosed rare genetic conditions. The large family evaluated in the present study was described in 1966 and now expands the phenotype of a known neuromuscular gene. OBJECTIVE: To determine the genetic cause of a slowly progressive, autosomal dominant, scapuloperoneal neuromuscular disorder by using linkage and exome sequencing. DESIGN, SETTING, AND PARTICIPANTS: Fourteen affected individuals in a 6-generation family with a progressive scapuloperoneal disorder were evaluated. Participants were examined at pediatric, neuromuscular, and research clinics from March 1, 2005, to May 31, 2014. Exome and linkage were performed in genetics laboratories of research institutions. MAIN OUTCOMES AND MEASURES: Examination and evaluation by magnetic resonance imaging, ultrasonography, electrodiagnostic studies, and muscle biopsies (n = 3). Genetic analysis included linkage analysis (n = 17) with exome sequencing (n = 7). RESULTS: Clinical findings included progressive muscle weakness in an initially scapuloperoneal and distal distribution, including wrist extensor weakness, finger and foot drop, scapular winging, mild facial weakness, Achilles tendon contractures, and diminished or absent deep tendon reflexes. Both age at onset and progression of the disease showed clinical variability within the family. Muscle biopsy specimens demonstrated type I fiber atrophy and trabeculated fibers without nemaline rods. Analysis of exome sequences within the linkage region (4.8 megabases) revealed missense mutation c.591C>A p.Glu197Asp in a highly conserved residue in exon 4 of ACTA1. The mutation cosegregated with disease in all tested individuals and was not present in unaffected individuals. CONCLUSIONS AND RELEVANCE: This family defines a new scapuloperoneal phenotype associated with an ACTA1 mutation. A highly conserved protein, ACTA1 is implicated in multiple muscle diseases, including nemaline myopathy, actin aggregate myopathy, fiber-type disproportion, and rod-core myopathy. To our knowledge, mutations in Glu197 have not been reported previously. This residue is highly conserved and located in an exposed position in the protein; the mutation affects the intermolecular and intramolecular electrostatic interactions as shown by structural modeling. The mutation in this residue does not appear to lead to rod formation or actin accumulation in vitro or in vivo, suggesting a different molecular mechanism from that of other ACTA1 diseases.
Subject(s)
Actins/genetics , Muscular Dystrophy, Emery-Dreifuss/genetics , Muscular Dystrophy, Emery-Dreifuss/physiopathology , Adult , Age of Onset , Child , Disease Progression , Exome/genetics , Genetic Linkage , Humans , Male , Muscular Dystrophy, Emery-Dreifuss/pathology , Mutation, Missense/genetics , Myopathies, Nemaline , Pedigree , PhenotypeABSTRACT
It has been recently reported that the p.His63Asp polymorphism of the HFE gene accelerates disease progression both in the SOD1 transgenic mouse and in amyotrophic lateral sclerosis (ALS) patients. We have evaluated the effect of HFE p.His63Asp polymorphism on the phenotype in 1351 Italian ALS patients (232 of Sardinian ancestry). Patients were genotyped for the HFE p.His63Asp polymorphism (CC, GC, and GG). All patients were also assessed for C9ORF72, TARDBP, SOD1, and FUS mutations. Of the 1351 ALS patients, 363 (29.2%) were heterozygous (GC) for the p.His63Asp polymorphism and 30 (2.2%) were homozygous for the minor allele (GG). Patients with CC, GC, and GG polymorphisms did not significantly differ by age at onset, site of onset of symptoms, and survival; however, in SOD1 patients with CG or GG polymorphism had a significantly longer survival than those with a CC polymorphism. Differently from what observed in the mouse model of ALS, the HFE p.His63Asp polymorphism has no effect on ALS phenotype in this large series of Italian ALS patients.
Subject(s)
Amyotrophic Lateral Sclerosis/genetics , Amyotrophic Lateral Sclerosis/mortality , Genetic Association Studies , Histocompatibility Antigens Class I/genetics , Membrane Proteins/genetics , Phenotype , Polymorphism, Genetic/genetics , Aged , Alleles , Animals , Disease Progression , Female , Hemochromatosis Protein , Humans , Italy/epidemiology , Male , Mice , Middle Aged , Superoxide Dismutase/genetics , Superoxide Dismutase-1 , Survival RateABSTRACT
IMPORTANCE: Myasthenia gravis is a chronic, autoimmune, neuromuscular disease characterized by fluctuating weakness of voluntary muscle groups. Although genetic factors are known to play a role in this neuroimmunological condition, the genetic etiology underlying myasthenia gravis is not well understood. OBJECTIVE: To identify genetic variants that alter susceptibility to myasthenia gravis, we performed a genome-wide association study. DESIGN, SETTING, AND PARTICIPANTS: DNA was obtained from 1032 white individuals from North America diagnosed as having acetylcholine receptor antibody-positive myasthenia gravis and 1998 race/ethnicity-matched control individuals from January 2010 to January 2011. These samples were genotyped on Illumina OmniExpress single-nucleotide polymorphism arrays. An independent cohort of 423 Italian cases and 467 Italian control individuals were used for replication. MAIN OUTCOMES AND MEASURES: We calculated P values for association between 8,114,394 genotyped and imputed variants across the genome and risk for developing myasthenia gravis using logistic regression modeling. A threshold P value of 5.0×10(-8) was set for genome-wide significance after Bonferroni correction for multiple testing. RESULTS: In the overall case-control cohort, we identified association signals at CTLA4 (rs231770; P=3.98×10(-8); odds ratio, 1.37; 95% CI, 1.25-1.49), HLA-DQA1 (rs9271871; P=1.08×10(-8); odds ratio, 2.31; 95% CI, 2.02-2.60), and TNFRSF11A (rs4263037; P=1.60×10(-9); odds ratio, 1.41; 95% CI, 1.29-1.53). These findings replicated for CTLA4 and HLA-DQA1 in an independent cohort of Italian cases and control individuals. Further analysis revealed distinct, but overlapping, disease-associated loci for early- and late-onset forms of myasthenia gravis. In the late-onset cases, we identified 2 association peaks: one was located in TNFRSF11A (rs4263037; P=1.32×10(-12); odds ratio, 1.56; 95% CI, 1.44-1.68) and the other was detected in the major histocompatibility complex on chromosome 6p21 (HLA-DQA1; rs9271871; P=7.02×10(-18); odds ratio, 4.27; 95% CI, 3.92-4.62). Association within the major histocompatibility complex region was also observed in early-onset cases (HLA-DQA1; rs601006; P=2.52×10(-11); odds ratio, 4.0; 95% CI, 3.57-4.43), although the set of single-nucleotide polymorphisms was different from that implicated among late-onset cases. CONCLUSIONS AND RELEVANCE: Our genetic data provide insights into aberrant cellular mechanisms responsible for this prototypical autoimmune disorder. They also suggest that clinical trials of immunomodulatory drugs related to CTLA4 and that are already Food and Drug Administration approved as therapies for other autoimmune diseases could be considered for patients with refractory disease.
Subject(s)
Genetic Predisposition to Disease , Genome-Wide Association Study , HLA-DQ alpha-Chains/genetics , Myasthenia Gravis/genetics , Adult , Age of Onset , CTLA-4 Antigen/genetics , Case-Control Studies , Female , Gene Frequency , Genotype , Humans , Male , Middle Aged , Polymorphism, Single Nucleotide/genetics , United StatesABSTRACT
MATR3 is an RNA- and DNA-binding protein that interacts with TDP-43, a disease protein linked to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Using exome sequencing, we identified mutations in MATR3 in ALS kindreds. We also observed MATR3 pathology in ALS-affected spinal cords with and without MATR3 mutations. Our data provide more evidence supporting the role of aberrant RNA processing in motor neuron degeneration.
Subject(s)
Amyotrophic Lateral Sclerosis/genetics , Family Health , Genetic Predisposition to Disease/genetics , Mutation/genetics , Nuclear Matrix-Associated Proteins/genetics , RNA-Binding Proteins/genetics , Aged , Aged, 80 and over , Amyotrophic Lateral Sclerosis/pathology , Computational Biology , DNA Mutational Analysis , DNA-Binding Proteins/metabolism , Female , Genotype , Humans , Male , Middle Aged , Muscle, Skeletal/metabolism , Muscle, Skeletal/pathology , Neurologic Examination , Nuclear Matrix-Associated Proteins/metabolism , RNA-Binding Proteins/metabolism , Spinal Cord/metabolism , Spinal Cord/pathologyABSTRACT
We recently reported that mutations in the valosin-containing protein (VCP) gene are a cause of 1%-2% of familial amyotrophic lateral sclerosis (ALS) cases, but their role in the pathogenesis of sporadic ALS is unclear. We undertook mutational screening of VCP in 701 sporadic ALS cases. Three pathogenic variants (p.Arg159Cys, p.Asn387Thr, and p.R662C) were found in three U.S. cases, each of whom presented with progressive upper and lower motor neuron signs consistent with definite ALS by El Escorial diagnostic criteria. Our data indicate that VCP mutations may underlie apparently sporadic ALS but account for <1% of this form of disease.
Subject(s)
Adenosine Triphosphatases/genetics , Amyotrophic Lateral Sclerosis/genetics , Cell Cycle Proteins/genetics , Mutation/genetics , Aged , Amyotrophic Lateral Sclerosis/epidemiology , Amyotrophic Lateral Sclerosis/physiopathology , DNA Mutational Analysis , Female , Humans , Italy , Male , Middle Aged , United States , Valosin Containing ProteinABSTRACT
OBJECTIVE: Genetic heterogeneity is common in many neurologic disorders. This is particularly true for the hereditary ataxias where at least 36 disease genes or loci have been described for spinocerebellar ataxia and over 100 genes for neurologic disorders that present primarily with ataxia. Traditional genetic testing of a large number of candidate genes delays diagnosis and is expensive. In contrast, recently developed genomic techniques, such as exome sequencing that targets only the coding portion of the genome, offer an alternative strategy to rapidly sequence all genes in a comprehensive manner. Here we describe the use of exome sequencing to investigate a large, 5-generational British kindred with an autosomal dominant, progressive cerebellar ataxia in which conventional genetic testing had not revealed a causal etiology. METHODS: Twenty family members were seen and examined; 2 affected individuals were clinically investigated in detail without a genetic or acquired cause being identified. Exome sequencing was performed in one patient where coverage was comprehensive across the known ataxia genes, excluding the known repeat loci which should be examined using conventional analysis. RESULTS: A novel p.Arg26Gly change in the PRKCG gene, mutated in SCA14, was identified. This variant was confirmed using Sanger sequencing and showed segregation with disease in the entire family. CONCLUSIONS: This work demonstrates the utility of exome sequencing to rapidly screen heterogeneous genetic disorders such as the ataxias. Exome sequencing is more comprehensive, faster, and significantly cheaper than conventional Sanger sequencing, and thus represents a superior diagnostic screening tool in clinical practice.