Readjusting the localization of merosin (laminin alpha 2-chain) deficient congenital muscular dystrophy locus on chromosome 6q2.

The laminin alpha 2-chain gene mutations (LAMA2) are responsible for about 50% of the cases of classical congenital muscular dystrophy. These patients form a clinically homogenous group presenting merosin (laminin alpha 2-chain) deficiency in muscle biopsies. The LAMA2 gene has been previously localized on 6q22-23 and the disease locus mapped in a 16 cM interval in 6q2 by homozygosity mapping. In the present report we establish, by haplotyping additional microsatellites markers in 18 consanguineous families, that LAMA2 gene is more centromeric than previously thought: between the flanking markers, D6S407 and D6S1705, distant of 3 cM. In this interval the microsatellite D6S1620 is homozygous for all the patients. The localization of LAMA2 gene was confirmed by radiation hybrid mapping. The 3 new highly informative markers can be very useful for prenatal diagnosis.