Haplotype analysis of genomic polymorphisms in and around the myotonic dystrophy locus in diverse populations of India

The frequencies of haplotypes based upon the (CTG)(n) repeat and three othe r biallelic markers in and around the myotonic dystrophy (DM) locus were es timated in 13 ethnically, linguistically and geographically diverse sub-pop ulations of India. The range of CTG repeats in caste populations was 5-31, while in tribal populations the range was shorter (5-23). Extensive variati on in frequencies of large (CTG)(n) alleles (greater than or equal to 18 re peats) was found in Indian populations. The implications of this finding on DM epidemiology are discussed. Haplotype diversity was found to be very hi gh in most populations. The majority of the Indian DM patients carried a ha plotype that is commonly found among DM patients globally; this is the most common haplotype in the class of large (greater than or equal to 18 repeat s) CTG alleles. However, one haplotype was found to be present in particula rly high frequency in Indian populations; this haplotype was also found amo ng Indian DM patients. This haplotype may be a characteristic of Indian and possibly of other East Asian populations.