부산대학교 도서관

Vertebrate muscle development begins with the patterning of the paraxial mesoderm by inductive signals from midline tissues, resulting in myotome formation. Subsequently, growth occurs as new muscle fibers are added. We show that in zebrafish new slow muscle fibers are first added at the end of the segmentation period in growth zones near the dorsal and ventral extremes of the myotome. We have tested whether these newly added slow muscle fibers require an architecture of embryonic slow muscle fibers to support their development and whether their fate is regulated by the same mechanisms that regulate embryonic muscle fates. We previously demonstrated that Hedgehog signaling through the slow-muscle-omitted gene product is required for the specification of embryonic slow muscle fibers. Here, we show that in the absence of Hh signaling, new slow muscle fibers differentiate in the larva at the correct time and place, despite the complete absence of embryonic slow muscle fibers to serve as a scaffold for the addition of new slow muscle fibers. We conclude that the mechanisms regulating the slow muscle cell fate during the embryonic and larval periods are different.