Meiotic drive at the myotonic dystrophy locus

Gennarelli, MD, B.; Baiget, M.; Martorell, L.; Novelli, G.,  Journal of Medical Genetics,  31:980-980. 1994.

The mutation underlying myotonic dystrophy (DM, MIM* 160900) is the expansion of a CTG trinucleotide repeat sequence at the 3′ untranslated region of a protein kinase gene (MT-PK).’ The kinetics of this process is influenced by the sex of the transmitting parent and size of the parental allele.2 Congenital DM (CDM) occurs almost always with maternal transmission. Only two patients with CDM have proven paternal inheritance.5′ Maternal transmission is considered to be the result of a large intergenerational increase of the CTG repeat size,7 while repeat length contractions are more likely inherited if the mutated allele is of paternal origin.8 However, the range of expansions is wider for alleles transmitted by fathers with fewer than 100 repeats (range 41 to 95).9 This has suggested a male bias in the generation of new contracted or expanded DM alleles.’° Carey et all’ described an unusual segregation of the MT-PK alleles with a CTG number > 19 in healthy persons heterozygous for repeats in the wild type size range, and suggested the possibility of meiotic drive at the DM locus