Dystrophin and Dp71, two products of the DMD gene, show a different pattern of expression during embryonic development in zebrafish

Dystrophin, the protein defective in Duchenne muscular dystrophy (DMD), plays a critical role in the formation and maintenance of the neuromuscular junction. In addition to dystrophin, activation of internal promoters of the DMD gene leads to the production of several short products. Among these, Dp71, which consists of the C-terminal domain of dystrophin, is the most abundant product of the gene in non-muscle tissues and brain. In this report, we compare the temporal and regional expression patterns of dystrophin and Dp71 at different stages of embryonic development and during retinal differentiation in zebrafish. The Dp71 transcripts are the earliest to be expressed at 9-10 h post-fertilization (hpf) in the axial mesoderm. As development proceeds, intense Dp71 staining is observed in the notochord, the developing brain, the marginal regions of the somites and the eye primordium. At the completion of retinal differentiation, Dp71 is expressed in the ganglion and inner nuclear layers. Transcripts encoding dystrophin have a slightly later onset of expression, 13-14 hpf, and remain restricted to the transverse myosepta through all the developmental stages examined. The complementary patterns of expression of dystrophin and Dp71 suggest that these two proteins exert different functions during embryonic development in zebrafish.