SummarySpinocerebellar ataxia type 12 (SCA12) is an autosomal dominant cerebellar ataxia associated with the expansion of an unstable CAG repeat in the 5 region of the PPP2R2B gene on chromosome 5q31-5q32. We found that it accounts for ∼ 16% (20/124) of all the autosomal dominant ataxia cases diagnosed in AIIMS, a major tertiary referral centre in North India. The length of the expanded allele in this population ranges from 51-69 CAG triplets. Interestingly, all the affected families belong to an endogamous population, which originated in the state of Haryana, India. We identified four novel SNPs and a dinucleotide marker spanning ∼ 137 kb downstream of CAG repeat in the PPP2R2B gene. Analysis of 20 Indian SCA12 families and ethnically matched normal unrelated individuals revealed one haplotype to be significantly associated with the affected alleles (P = 0.000), clearly indicating the presence of a common founder for SCA12 in the Indian population. This haplotype was not shared by the American pedigree with SCA12. Therefore, the SCA12 expansion appears to have originated at least twice.

Twenty autosomal markers, including linked markers at two gene markers, are used to understand the genomic similarity and diversity among three tribal (Paite, Thadou, and Kom) and one nontribal communities of Manipur (Northeast India). Two of the markers (CD4 and HB9) are monomorphic in Paite and one (the CD4 marker) in Kom. Data suggest the Meitei (nontribal groups) stand apart from the three tribal groups with respect to higher heterozygosity (0.366) and presence of the highest ancestor haplotypes of DRD2 markers (0.228); this is also supported by principal co-ordinate analysis. These populations are found to be genomically closer to the Chinese population than to other Indian populations.

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Although the presently studied populations of Andhra Pradesh have heterozygosity similar to that of Nilgiri hill populations, the former are more closely placed on the PCO plot than the latter, who are more scattered. Also the gene differentiation (Gst) of the former is much lower than that of the latter, indicating considerable regional variation in the inflow of genes from diverse ethnic groups within south India.

Families of 20 probands with atlanto-occipital fusion were studied, and the neurological complications in these patients described. In X-ray studies of 115 close relatives, 4 additional cases (3.5%) with the same anomaly were detected. In a comparison of adult patients with closely related age- and sex-matched controls, all anthropological measurements except length and breadth of the head tended to be smaller in the patients; for height, weight, leg and foot length, and the robusticity index, these differences were statistically significant.

The present study analyses the potential role of MTHFR gene polymorphism, folate supplementation and dietary pattern among the mothers of NTD neonates and controls in heterogeneous populations of North India, with the special focus on their ethnic labels. Results indicated significant increased risk for neural tube defects with respect to low folic acid supplementation and vegetarian diet in univariate and multivariate analyses. There was no significant difference in the genotypic or allelic distribution of MTHFR C677T polymorphism, however, high frequency of CT genotype, as observed, among controls suggests heterozygous advantage probably due to supplementary folate. Among the two communities, Muslim NTD mothers had higher TT genotype showing increased risk for neural tube defects (adjusted OR: 12.9; 95% CI: 1.21-136.8) and lower folic acid supplementation (adjusted OR: 3.5; 95% CI: 1.18-10.22). Whereas, marginal increased risk for NTDs with vegetarian diet was observed among Hindus. Cultural and ethnic variation in the risk factors for neural tube defects is highlighted in the study.

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Methylenetetrahydrofolate reductase (MTHFR) is a vital enzyme catalyzing the nicotinamide adenine dinucleotide phosphate (NADPH) linked reduction of 5,10-methylenetetrahydrofolate to 5-methylenetetrahydrofolate, which serves as cofactor in methylation of homocysteine to methionine. Three clinically important mutations of the MTHFR gene namely C677T, A1298C, and T1317C are reported to be associated with various pathological conditions. The present study deals with the screening of C677T mutation among two endogamous groups viz. Ahirs and Jats of Haryana (India). The mutation is reported to be significantly associated with thrombosis, hypertension, stroke and myocardial infraction, neural tube defects (NTDs), and recurrent pregnancy loss. The T allele among Jats is found to be more frequent (0.06) than Ahirs (0.03). Moreover, the Jats population shows a significant deviation from Hardy-Weinberg equilibrium with respect to C677T mutation. This could probably be due to some selection pressure operating in the population.