In vitro transdifferentiation of striated muscle to smooth muscle cells of a medusa.

Mononucleated striated muscle cells can be isolated from anthomedusae and cultivated in artificial seawater. In the cultivated muscle the differentiated state is maintained and DNA synthesis is not observed. The isolated striated muscle can be activated by collagenase treatment to transdifferentiate into various new cell types. Between the second and third day following collagenase treatment DNA synthesis is initiated, and mitosis and de novo flagellum formation occur in the isolated muscle. Under these circumstances all isolated striated muscle fragments produce both smooth muscle cells and y-cells (Schmid and Alder, 1984). In experiments, in which either transcription (actinomycin D) or translation (cycloheximide) is inhibited, the activated striated muscle cells do not transdifferentiate but maintain their differentiated state. Inhibition of DNA replication (aphidicolin), however, results in uniform transdifferentiation of striated muscle to smooth muscle cells in the absence of y-cell types (Schmid and Alder, 1984). The fluorescence stain NBD-phallacidin is used to monitor the characteristic change of F-actin pattern of these isolates.