Long-range genomic map of the Duchenne muscular dystrophy (DMD) gene: isolation and use of J66 (DXS268), a distal intragenic marker.

By cloning the endpoints of a DMD-associated deletion, we have "jumped" 1100 kb from pERT87-1 (DSX164) to a new locus designated J66 (DXS268), mapping distally within the Duchenne muscular dystrophy (DMD) gene. Both J66 and JBir are mapped by field-inversion gel electrophoresis and detect abnormal SfiI fragments in DMD patients and distal DMD-associated X; autosome translocations. Our long-range map extends the physical map of the DMD gene from 800 to 2000 kb (2 Mb) and increases the mapped portion of Xp21 to approximately 8 Mb. The position of the glycerol kinase gene and the adrenal hypoplasia locus are further confined to the region between J66 and the nearest distal probe L1-4. This region spans at least 1.5 Mb. The multiallelic J66 polymorphism has immediate application in the diagnosis of DMD and generally appears to be distal to DMD mutations.