Molecular analysis of Huntington's disease and linked polymorphisms in the Indian population

Objectives - To understand the population variation and haplotypes of Huntington's disease (HD) in India we have analysed CAG repeats at the HD locus together with closely linked polymorphisms in both HD patients and normal controls. Materials and methods - The CAG repeat and linked polymorphisms were analysed in 30 Indian HD families together with 250 ethnically matched controls using fluorescent polymerase chain reaction (PCR) based size estimation. Results - CAG repeats at the HD locus in the normal population showed a mean size of 17.99 +/- 2.66 repeats ( range nine to 33 repeats). The HD mutation in our families did not show any significant association with either the (CCG)(7) or (CCG)(10) allele while haplotype analysis suggested the over-representation of the 7-2-I (CCG-D4s127-Delta2642 loci) haplotype in a subset of families. Conclusion - The distribution of CAG repeats in the normal population suggests a higher prevalence of HD, closer to that seen in Western Europe. Haplotype analysis suggests the presence of a founder mutation in a subset of families and provides evidence for multiple and geographically distinct origins for the HD mutation in India.