Carrier detection in non-deletional Duchenne/Becker muscular dystrophy families using polymorphic dinucleotide (CA) repeat loci of dystrophin gene.

ABSTRACT

BACKGROUND & OBJECTIVES: Carrier detection and prenatal diagnosis is of great importance for families with one or more sons affected with Duchenne/Becker muscular dystrophy (D/BMD). In about 35-40 per cent of these patients, the causative mutation does not involve gross rearrangement in the structure of dystrophin gene. In these non-deletional families, genetic counselling can be provided only by linkage analysis. The aim of the present study was to determine the carrier status of female relatives in north Indian families with non-deletional D/BMD using highly polymorphic intragenic dinucleotide (CA) repeat markers. METHODS: Six short tandem repeats (STRs) spanning 5' (1), central (4) and 3' regions of the dystrophin gene were used to analyse 14 unrelated families comprising 68 individuals with 12 female siblings at risk of being carriers. RESULTS: Five female siblings inherited at risk STR haplotype, six inherited normal haplotype and one had meiotic recombination. The intragenic recombinations were observed in three families at the central region STR loci and in one family between the proximal and central regions of the gene. INTERPRETATION & CONCLUSIONS: Our study suggested that at least 6 STR markers spanning 5', central and 3' regions of the dystrophin gene are essential to ascertain one or more informative loci and to rule out recombinations in non-deletional D/BMD families for carrier analysis.