Novel TCAP mutation c.32C>A causing limb girdle muscular dystrophy 2G

TCAP encoded telethonin is a 19 kDa protein, which plays an important role in anchoring titin in Z disc of the sarcomere and is known to cause LGMD2G, a rare muscle disorder characterised by proximal and distal lower limb weakness, calf hypertrophy and loss of ambulation. A total of 300 individuals with ARLGMD were recruited for this study. Among these we identified 8 clinically well characterised LGMD2G cases from 7 unrelated Dravidian families. Clinical examination revealed predominantly proximo - distal form of weakness, scapular winging, muscle atrophy, calf hypertrophy and foot drop, immunoblot showed either complete absence or severe reduction of telethonin. Genetic analysis revealed a novel nonsense homozygous mutation c.32C>A, p.(Ser11*) in three patients of a consanguineous family and an 8 bp homozygous duplication c.26_33dupAGGTGTCG, p.(Arg12fs31*) in another patient. Both mutations possibly lead to truncated protein or nonsense mediated decay. We could not find any functionally significant TCAP mutation in the remaining 6 samples, except for two other polymorphisms, c.453A>C, p.( = ) and c.-178G>T, which were found in cases and controls. This is the first report from India to demonstrate TCAP association with LGMD2G

Congenital myasthenic syndrome with mild intellectual disability caused by a recurrent SLC25A1 variant

Abstract: Congenital myasthenic syndromes (CMS) are a clinically and genetically heterogeneous group of disorders caused by mutations which lead to impaired neuromuscular transmission. SLC25A1 encodes a mitochondrial citrate carrier, associated mainly with the severe neurometabolic disease combined D-2- and L-2-hydroxyglutaric aciduria (D/L-2-HGA). We previously reported a single family with a homozygous missense variant in SLC25A1 with a phenotype restricted to relatively mild CMS with intellectual disability, but to date no additional cases of this CMS subtype had been reported. Here, we performed whole exome sequencing (WES) in three additional and unrelated families presenting with CMS and mild intellectual disability to identify the underlying causative gene. The WES analysis revealed the presence of a homozygous c.740G>A; p.(Arg247Gln) missense SLC25A1 variant, the same SLC25A1 variant as identified in the original family with this phenotype. Electron microscopy of muscle from two cases revealed enlarged and accumulated mitochondria. Haplotype analysis performed in two unrelated families suggested that this variant is a result of recurrent mutation and not a founder effect. This suggests that p.(Arg247Gln) is associated with a relatively mild CMS phenotype with subtle mitochondrial abnormalities, while other variants in this gene cause more severe neurometabolic disease. In conclusion, the p.(Arg247Gln) SLC25A1 variant should be considered in patients presenting with a presynaptic CMS phenotype, particularly with accompanying intellectual disability

TEFM variants impair mitochondrial transcription causing childhood-onset neurological disease

Mutations in the mitochondrial or nuclear genomes are associated with a diverse group of human disorders characterized by impaired mitochondrial respiration. Within this group, an increasing number of mutations have been identified in nuclear genes involved in mitochondrial RNA biology. The TEFM gene encodes the mitochondrial transcription elongation factor responsible for enhancing the processivity of mitochondrial RNA polymerase, POLRMT. We report for the first time that TEFM variants are associated with mitochondrial respiratory chain deficiency and a wide range of clinical presentations including mitochondrial myopathy with a treatable neuromuscular transmission defect. Mechanistically, we show muscle and primary fibroblasts from the affected individuals have reduced levels of promoter distal mitochondrial RNA transcripts. Finally, tefm knockdown in zebrafish embryos resulted in neuromuscular junction abnormalities and abnormal mitochondrial function, strengthening the genotype-phenotype correlation. Our study highlights that TEFM regulates mitochondrial transcription elongation and its defect results in variable, tissue-specific neurological and neuromuscular symptoms

Genetic landscape of congenital insensitivity to pain and hereditary sensory and autonomic neuropathies

Congenital insensitivity to pain (CIP) and hereditary sensory and autonomic neuropathies (HSAN) are clinically and genetically heterogeneous disorders exclusively or predominantly affecting the sensory and autonomic neurons. Due to the rarity of the diseases and findings based mainly on single case reports or small case series, knowledge about these disorders is limited. Here, we describe the molecular workup of a large international cohort of CIP/HSAN patients including patients from normally under-represented countries. We identify 80 previously unreported pathogenic or likely pathogenic variants in a total of 73 families in the >20 known CIP/HSAN-associated genes. The data expand the spectrum of disease-relevant alterations in CIP/HSAN, including novel variants in previously rarely recognized entities such as ATL3-, FLVCR1- and NGF-associated neuropathies and previously under-recognized mutation types such as larger deletions. In silico predictions, heterologous expression studies, segregation analyses and metabolic tests helped to overcome limitations of current variant classification schemes that often fail to categorize a variant as disease-related or benign. The study sheds light on the genetic causes and disease-relevant changes within individual genes in CIP/HSAN. This is becoming increasingly important with emerging clinical trials investigating subtype or gene-specific treatment strategies

Neuromuscular disease genetics in under-represented populations: increasing data diversity

Neuromuscular diseases (NMDs) affect ∼15 million people globally. In high income settings DNA-based diagnosis has transformed care pathways and led to gene-specific therapies. However, most affected families are in low-to-middle income countries (LMICs) with limited access to DNA-based diagnosis. Most (86%) published genetic data is derived from European ancestry. This marked genetic data inequality hampers understanding of genetic diversity and hinders accurate genetic diagnosis in all income settings. We developed a cloud-based transcontinental partnership to build diverse, deeply-phenotyped and genetically characterized cohorts to improve genetic architecture knowledge, and potentially advance diagnosis and clinical management. We connected 18 centres in Brazil, India, South Africa, Turkey, Zambia, Netherlands and the UK. We co-developed a cloud-based data solution and trained 17 international neurology fellows in clinical genomic data interpretation. Single gene and whole exome data were analysed via a bespoke bioinformatics pipeline and reviewed alongside clinical and phenotypic data in global webinars to inform genetic outcome decisions. We recruited 6001 participants in the first 43 months. Initial genetic analyses ‘solved’ or ‘possibly solved’ ∼56% probands overall. In-depth genetic data review of the four commonest clinical categories (limb girdle muscular dystrophy, inherited peripheral neuropathies, congenital myopathy/muscular dystrophies and Duchenne/Becker muscular dystrophy) delivered a ∼59% ‘solved’ and ∼13% ‘possibly solved’ outcome. Almost 29% of disease causing variants were novel, increasing diverse pathogenic variant knowledge. Unsolved participants represent a new discovery cohort. The dataset provides a large resource from under-represented populations for genetic and translational research. In conclusion, we established a remote transcontinental partnership to assess genetic architecture of NMDs across diverse populations. It supported DNA-based diagnosis, potentially enabling genetic counselling, care pathways and eligibility for gene-specific trials. Similar virtual partnerships could be adopted by other areas of global genomic neurological practice to reduce genetic data inequality and benefit patients globally

Neuromuscular disease genetics in underrepresented populations : increasing data diversity

DATA AVAILABILITY : At the end of the study, participants de-identified exome and genome data will be archived in the European Molecular Biology Laboratory European Bioinformatics Institute’s European Genome-Phenome Archive (EMBL EBI EGA), with community access to this and selected de-identified REDCap data managed via an ICGNMD Data Access Committee.Neuromuscular diseases (NMDs) affect ∼15 million people globally. In high income settings DNA-based diagnosis has transformed care pathways and led to gene-specific therapies. However, most affected families are in low-to-middle income countries (LMICs) with limited access to DNA-based diagnosis. Most (86%) published genetic data is derived from European ancestry. This marked genetic data inequality hampers understanding of genetic diversity and hinders accurate genetic diagnosis in all income settings. We developed a cloud-based transcontinental partnership to build diverse, deeply-phenotyped and genetically characterized cohorts to improve genetic architecture knowledge, and potentially advance diagnosis and clinical management. We connected 18 centres in Brazil, India, South Africa, Turkey, Zambia, Netherlands and the UK. We co-developed a cloud-based data solution and trained 17 international neurology fellows in clinical genomic data interpretation. Single gene and whole exome data were analysed via a bespoke bioinformatics pipeline and reviewed alongside clinical and phenotypic data in global webinars to inform genetic outcome decisions. We recruited 6001 participants in the first 43 months. Initial genetic analyses 'solved' or 'possibly solved' ∼56% probands overall. In-depth genetic data review of the four commonest clinical categories (limb girdle muscular dystrophy, inherited peripheral neuropathies, congenital myopathy/muscular dystrophies and Duchenne/Becker muscular dystrophy) delivered a ∼59% 'solved' and ∼13% 'possibly solved' outcome. Almost 29% of disease causing variants were novel, increasing diverse pathogenic variant knowledge. Unsolved participants represent a new discovery cohort. The dataset provides a large resource from under-represented populations for genetic and translational research. In conclusion, we established a remote transcontinental partnership to assess genetic architecture of NMDs across diverse populations. It supported DNA-based diagnosis, potentially enabling genetic counselling, care pathways and eligibility for gene-specific trials. Similar virtual partnerships could be adopted by other areas of global genomic neurological practice to reduce genetic data inequality and benefit patients globally.This work was supported by a Medical Research Council strategic award to establish an International Centre for Genomic Medicine in Neuromuscular Diseases (ICGNMD) MR/S005021/1. Additional ICGNMD support including travel and subsistence costs was received from the National Brain Appeal (UK Charity 290173) and University College London Global Engagement Funds. Fellowships for R.S.S.F. and K.N. were funded by the Guarantors of Brain (UK Charity 1197319). The authors acknowledge and are grateful for: conference bursaries from the World Muscle Society to R.S.S.F. S.R., K.N., O.Y.K., P.J.T., V.V.Y. S.V.D.M. and R.L. are members of the European Reference Network for Rare Neuromuscular Diseases (ERN EURO-MND). M.P.K.: National Institute of Neurological Disorders and Stroke (1K23NS112463), American Association of Neuromuscular & Electrodiagnostic Medicine Development Award and Allen Foundation. D.B.: National Institute of Neurological Disorders and Stroke (K23NS117310) and support from Biogen for the KCTN1 Natural History Study. G.M.R.: University College London and UCLH Biomedical Research Centre funding, Health Education England and University College London Hospitals NHS Foundation Trust Innovation Fund. R.M.F., R.W.T. and K.P.: Wellcome core support (203105/Z/16/Z). R.M.F. received additional support from the Lily Foundation and the Leigh Syndrome International Consortium. A.T.: EU Horizon 2020 research and innovation Solve-RD project, No. 779257. F.H.W., M.S., M.B. and A.V.: South African Medical Research Council award ‘The genetics of Neuromuscular Diseases in South African patient populations: the ICGNMD study’. K.T. is funded by a J. C. Bose Fellowship, Science and Engineering Research Board (SERB) Department of Science and Technology, India. P.G. is supported by the Centre for DNA Fingerprinting and Diagnostics (CDFD) Core Research Grant, Department of Biotechnology, Government of India. R.H.: Wellcome award 109915/Z/15/Z, UK Medical Research Council award MR/N025431/1, the Lily Foundation, Evelyn Trust Research Grant (Ref 19/14), Action for A-T and UK Research and Innovation Newton Fund (MR/NO27302/1). P.F.C.: Wellcome awards 212219/Z/18/Z and 224486/Z/21/Z, UK Medical Research Council awards MC_PC_21046, MR/S035699/1 and MR/ S01165X/1, LifeArc Philanthropic Fund, NIHR BioResource for Translational Research in Common and Rare Diseases, Alzheimer’s Society, NIHR BioResource for Genes and Cognition and Leverhulme Trust. R.D.S.P.: UK Medical Research Council MR/ S002065/1 and MC_PC_21046, and the Lily Foundation. H.H.: UK Medical Research Council, Wellcome, UCLH Biomedical Research Centre (NIHR-BRC), Rosetrees Trust, and SOLVE-RD. M.M.R.: Wellcome grant G104817, National Institute of Neurological Disorders and Stroke and Office of Rare Diseases grants U54NS065712 and 1UOINS109403-01 and Muscular Dystrophy Association grant.https://www.edusoft.ro/brain/index.php/brainam2024Paediatrics and Child HealthSDG-03:Good heatlh and well-bein

Neuropsychological deficits in amyotrophic lateral sclerosis (ALS): a South India experience

ALS is a terminal progressive degenerative neurological disorder studies suggest that approximately 35% to 52% of ALS patients experience cognitive deficits which may be identified early in the course of the disease. Cognitive deficits being the integral part of the disease has not been studied in the Indian setting. This is one of the first studies assessing the pattern of cognitive impairment in ALS in the Indian condition. The objective is to examine the neuropsychological profile of amyotrophic lateral sclerosis. Cognitive function was studied in 20 ALS patients: mean age 45.85±13.9 years (22-65). Neuropsychological test battery was administered. In all 21 test were administered individually in 4-5 sessions which lasted for 7-8 hours. The results show that the majority of patients were from lower/middle socio-economic background. Scores were compared with gender, age and education specific norms, wherein scores falling below 15th percentile of the normative data were treated as deficits. ALS-associated cognitive impairments include deficiencies in visual attention, working memory, fluency, cognitive flexibility, response inhibition, planning, problem solving, and visual-perceptual skills.These impairments indicate executive dysfunction. In conclusion ALS is a disease that affects higher cognitive frontal functions, especially the EF