LOCALIZATION OF MEROSIN-NEGATIVE CONGENITAL MUSCULAR-DYSTROPHY TO CHROMOSOME 6Q2 BY HOMOZYGOSITY MAPPING

Congenital muscular dystrophies (CMD) are autosomal recessive, heterog eneous disorders. The commonest forms are the Fukuyama CMD (FCMD), ass ociated with mental retardation and structural brain anomalies, and cl assical (occidental) CMD, with pure muscle expression. FCMD has been l ocalized to chromosome 9q31 - q33. Following the discovery of merosin deficiency in some CMD cases, we have localized, by homozygosity mappi ng and linkage analysis(Zmax = 5.6; theta = 0.0 for marker AFM127xb2) in four merosin-negative families a CMD gene in a 16 cM region of chro mosome 6q2 in the region of the laminin M chain gene. In three consang uineous, merosin-positive, CMD families there was no linkage to either chromosome 6q2 or 9q31 - q33.