Expression of the putative Duchenne muscular dystrophy gene in differentiated myogenic cell cultures and in the brain.

Duchenne muscular dystrophy (DMD), a sex-linked degenerative disorder of the muscle, is one of the most common lethal genetic diseases in man. It affects about one male in 3,500, with an estimated one-third of cases being caused by new mutations. A less severe disease, Becker's muscular dystrophy (BMD), maps to the same chromosomal locus and is most probably an allelic form of DMD. Both diseases are sometimes associated with various degrees of mental retardation; the molecular basis of these phenotypes is unknown (for review, see ref. 1). The giant DMD gene spans approximately 2,000 kilobases (kb) (0.05% of the human genome) and encodes a 14-kb mRNA. The tissue-specificity of its expression has not been precisely determined. Monaco et al., using Northern blots, reported expression of the gene in human fetal skeletal muscle and small intestine but not in human fetal brain, or in human cultured myoblasts and transformed B and T cells. More recently, expression was detected in mouse skeletal and cardiac muscle, but not in mouse brain. Here we show, using a ribonuclease protection assay, that the DMD gene is developmentally regulated in rat and mouse myogenic cell cultures, and that it is expressed in rat and mouse striated muscle, in mouse smooth muscle and in rat, mouse and rabbit brain. We could not detect transcripts in other non-muscle tissues.