ACTIVATION OF THE GENE ENCODING THE GLYCOLYTIC ENZYME BETA-ENOLASE DURING EARLY MYOGENESIS PRECEDES AN INCREASED EXPRESSION DURING FETAL MUSCLE DEVELOPMENT

We define the spatial and temporal patterns of expression of the gene encoding the glycolytic enzyme, beta-enolase, during mouse ontogenesis. Transcripts were detected by in situ hybridization using S-35 labelled cRNA probes. The beta-enolase gene is expressed only in striated muscles. It is first detected in the embryo, in the cardiac tube and in newly formed myotomes. In the muscle masses of the limb, beta-gene expression occurs at a low level in primary fibers, and subsequently greatly increases at a time which corresponds to the onset of innervation and secondary fiber formation. Later in development, it becomes undetectable in slow-twitch fibers. Our results demonstrate the multistep regulation of the beta-enolase gene. The regulation of this muscle-specific gene in somites is discussed in terms of the myogenic sequences of the MyoD family shown to be present when it is activated.