RESUMO
BACKGROUND: The ethnic diversity of India provides a unique opportunity to study the history of the origin of mutations of genetic disorders. Spinocerebellar ataxia type 27B (SCA27B), a recently identified dominantly inherited cerebellar disorder is caused by GAA-repeat expansions in intron 1 of Fibroblast Growth Factor 14 (FGF14). Predominantly reported in the European population, we aimed to screen this mutation and study the founder haplotype of SCA27B in Indian ataxia patients. METHODS: We have undertaken screening of GAA repeats in a large Indian cohort of ~ 1400 uncharacterised ataxia patients and kindreds and long-read sequencing-based GAA repeat length assessment. High throughput genotyping-based haplotype analysis was also performed. We utilized ~ 1000 Indian genomes to study the GAA at-risk expansion alleles. FINDINGS: We report a high frequency of 1.83% (n = 23) of SCA27B in the uncharacterized Indian ataxia cohort. We observed several biallelic GAA expansion mutations (n = 5) with younger disease onset. We observed a risk haplotype (AATCCGTGG) flanking the FGF14-GAA locus over a 74 kb region in linkage disequilibrium. We further studied the frequency of this risk haplotype across diverse geographical population groups. The highest prevalence of the risk haplotype was observed in the European population (29.9%) followed by Indians (21.5%). The observed risk haplotype has existed through ~ 1100 generations (~ 22,000 years), assuming a correlated genealogy. INTERPRETATION: This study provides valuable insights into SCA27B and its Upper Paleolithic origin in the Indian subcontinent. The high occurrence of biallelic expansion is probably relevant to the endogamous nature of the Indian population.
RESUMO
Data are limited on the genetic profile of primary ciliary dyskinesia (PCD) from developing countries. Here, we report one of the first study on genetic profile of patients with suspected PCD from India. In this prospective cross-sectional study, we enrolled 162 children with suspected PCD. We recorded clinical features, relevant laboratory tests for PCD and performed whole exome sequencing (WES). We are reporting 67 patients here who had positive variant/s on WES. We had 117 variants in 40 genes among 67 patients. Among the 108 unique variants, 33 were categorized as pathogenic or likely pathogenic (P/LP). We had nine novel variants in out cohort. The 29 definite PCD cases, diagnosed by composite reference standards, had variants in 16 genes namely LRRC6/DNAAF11 (5), DNAH5 (3), CCDC39 (3), HYDIN (3), DNAH11 (2), CCDC40 (2), CCDC65 (2) and one each DNAAF3, DNAAF2, CFAP300, RPGR, CCDC103, CCDC114, SPAG1, DNAI1, and DNAH14. To conclude, we identified 108 unique variants in 40 genes among 67 patients. The common genes involved in definite cases of PCD in Indian patients were LRRC6, DNAH5, CCDC39, and HYDIN. Our findings suggest a need to develop a separate genetic panel for PCD in the Indian population.
