Molecular anatomy of CTG expansion in myotonin protein kinase gene among myotonic dystrophy patients from eastern India

Abstract

We have studied the CTG repeat sizes in the DMPK gene and six biallelic markers which are in complete linkage disequlibrium with Caucasian DM patients, to identify any common founder haplotype in 30 clinically diagnosed unrelated DM patients from eastern India. Our results revealed that in 27 patients (90%), CTG expansion took place on a DraIII(-) - HhaI(-) - Alu(+) - HinfI(+) - Fnu4H I(-) - TaqI(+) haplotype (haplotype I), similar to what have been published for Caucasoid and other DM patients. However, in three patients (10%), the expansion of CTG repeat was on DraIII(+) - HhaI(+) - Alu(+) - HinfI(-) - Fnu4H I(+) - TaqI(-) background (haplotype II), indicating a new haplotype. The distribution of haplotypes in 52 normal individuals of eastern India revealed that percentage of haplotypes I and II were 23.1% and 7.7% respectively in normal chromosomes. Haplotype II is absent among Caucasian DM patients as well as normal individuals indicating that this particular haplotype may be characteristic of the Indian population. Hum Mutat 16:372, 2000.