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Over 100 genetically distinct causal known loci for hereditary ataxia phenotype poses a challenge for diagnostic work‐up for ataxia patients in a clinically relevant time and precision. In the present study using next‐generation sequencing, we have investigated pathogenic variants in early‐onset cerebellar ataxia cases using whole exome sequencing in singleton/family‐designed and targeted gene‐panel sequencing. A total of 98 index patients were clinically and genetically (whole exome sequencing (WES) in 16 patients and targeted gene panel of 41 ataxia causing genes in 82 patients) evaluated. Four families underwent WES in family based design. Overall, we have identified 24 variants comprising 20 pathogenic and four likely‐pathogenic both rare/novel, variations in 21 early onset cerebellar ataxia patients. Among the identified variations, SACS (n = 7) and SETX (n = 6) were frequent, while ATM (n = 2), TTPA (n = 2) and other rare loci were observed. We have prioritized novel pathogenic variants in RARS2 and FA2H loci through family based design in two out of four families.

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Autosomal Dominant Cortical Tremor, Myoclonus and Epilepsy is a non-progressive disorder characterized by distal tremors. Autosomal Dominant Cortical Tremor, Myoclonus and Epilepsy has been reported globally with different genetic predispositions of autosomal dominant inheritance with a high degree of penetrance. In south India, Autosomal Dominant Cortical Tremor, Myoclonus and Epilepsy has been reported in a large cohort of 48 families, in which the genetic defect was not identified. This report pertains to the whole-genome analysis of four individuals followed by repeat-primed PCR for 102 patients from a familial cohort of 325 individuals. All the patients underwent extensive clinical evaluation including neuropsychological examinations. The whole-genome sequencing was done for two affected and two unaffected individuals, belonging to two different families. The whole-genome sequencing analysis revealed the repeat expansion of TTTTA and TTTCA in intron 4 of the SAMD12 gene located on chromosome 8 in the patients affected with Autosomal Dominant Cortical Tremor, Myoclonus and Epilepsy, whereas the unaffected family members were negative for the similar expansion. Further, the repeat-primed PCR analysis of 102 patients showed the expansion of the TTTCA repeats in the intron 4 of SAMD12 gene. All patients registered for this study belong to a single community called “Nadar” whose nativity is confined to the southern districts of India, with reported unique genetic characteristics. This is the largest and most comprehensive single report on clinically and genetically characterized Autosomal Dominant Cortical Tremor, Myoclonus and Epilepsy patients belonging to a unique ethnic group worldwide.

BackgroundGenetic factors may play a role in the susceptibility of Ischemic stroke (IS). Previous studies have shown that Tumour necrosis factor-α (TNF-α) gene polymorphisms were associated with the risk of IS in multiple ethnicities. The present case–control study tested the hypothesis that genetic polymorphisms of the TNF-α gene may affect the risk of IS in North Indian population. We investigated the association of four single nucleotide polymorphisms (− 308G/A, + 488G/A, − 857C/T and -1031 T/C) within TNF-α gene promoter and their haplotypes with the risk of IS.MethodsIS was classified using the Trial of Org 10,172 in Acute Stroke Treatment (TOAST) classification. Genotyping was performed for 250 IS patients and 250 age- and sex-matched IS free controls by using SNaPshot technique. Multivariate logistic regression was used to control the confounding effects of demographic and risk factor variables. Haplotype analyses were done by using PHASE software and Linkage disequilibrium (LD) analyses were done by using Haploview version 4.2 software.ResultsAn independent association between TNF-α + 488G/A (OR = 2.59; 95%CI 1.46 to 4.60; p = 0.001) and -857C/T (OR = 1.77; 95%CI 1.01 to 3.11; p < 0.04) and risk of IS was observed under dominant model. However, no significant association between -308G/A and -1031 T/C gene polymorphisms and risk of IS was observed. Haplotype analysis showed that A308-G488-C857-T1031 haplotypes were significantly associated with the increased risk of IS [OR = 1.66; 95%CI 1.02 to 2.71; p = 0.003]. Strong linkage disequilibrium (LD) was observed for + 488G/A and -857C/T (D’ = 0.41, r2 = 0.004).ConclusionsTwo SNPs (+ 488G/A and -857C/T) of TNF-α gene and their haplotypes are significantly associated with the risk of IS in the population enrolled from North India. Our findings indicate that polymorphisms and haplotypes of TNF-α gene may be used as a genetic marker for identifying individuals at increased risk for developing IS.

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The aim of this study was to assess the prevalence of pathogenic variants in the <i>SRD5A2</i> gene in children with 46,XY disorders of sex development (DSD) with normal to high serum testosterone levels and absence of Müllerian structures on imaging and to evaluate the genotype-phenotype correlation. Seventy-five patients with 46,XY DSD and probable clinical diagnosis of 5α-reductase 2 deficiency or androgen insensitivity syndrome were enrolled. Genetic analysis was done for pathogenic variants in <i>SRD5A2</i>, and the genotype-phenotype correlation was studied. As a result, 10 pathogenic or likely pathogenic biallelic variants in <i>SRD5A2, </i>either homozygous or compound heterozygous, were identified in 25 of 75 (33.3%) patients. The hCG stimulated testosterone: dihydrotestosterone (T:DHT) ratio was elevated in all patients with pathogenic variants in <i>SRD5A2</i> and in nearly 90% of those without pathogenic variants in <i>SRD5A2</i> in whom this was assessed. The missense pathogenic variant p.R246Q was a hotspot. One novel pathogenic variant p.Y178*, and a variant p.F194I, not previously reported in patients with 5α-reductase 2 deficiency, were identified. The missense variant p.F194I was predicted as deleterious and damaging by in silico analysis and as likely to reduce the enzyme activity by protein modeling. In conclusion, pathogenic variants in <i>SRD5A2 </i>can be detected in a wide spectrum of Indian patients with 46,XY DSD. Molecular genetic analysis should be considered as a first-line test as the T:DHT ratio lacks specificity and a hotspot variant is present in a vast majority.

Cerebellar ataxias (CAs) represent a group of autosomal dominant and recessive neurodegenerative disorders affecting cerebellum with or without spinal cord. Overall, CAs have preponderance for tandem nucleotide repeat expansions as an etiological factor (10 TREs explain nearly 30–40% of ataxia cohort globally). The experience of 10 years of common genetic ataxia subtypes for ≈5600 patients’ referrals (Pan‐India) received at a single center is shared herein. Frequencies (in %, n) of SCA types and FRDA in the sample cohort are observed as follows: SCA12 (8.6%, 490); SCA2 (8.5%, 482); SCA1 (4.8%, 272); SCA3 (2%, 113); SCA7 (0.5%, 28); SCA6 (0.1%, 05); SCA17 (0.1%, 05), and FRDA (2.2%, 127). A significant amount of variability in TRE lengths at each locus is observed, we noted presence of biallelic expansion, co‐occurrence of SCA‐subtypes, and the presence of premutable normal alleles. The frequency of mutated GAA‐FRDA allele in healthy controls is 1/158 (0.63%), thus an expected FRDA prevalence of 1:100 000 persons. The data of this study are relevant not only for clinical decision making but also for guidance in direction of genetic investigations, transancestral comparison of genotypes, and lastly provide insight for policy decision for the consideration of SCAs under rare disease category.