Spatiotemporal Expression of Connexin 39 and -43 During Myoblast Differentiation in Cultured Cells and in the Mouse Embryo

Connexin39 (Cx39) and connexin43 (Cx43) are known to be expressed during development of skeletal muscles. Here we have compared the expression pattern of both connexins during differentiation of established C₂C₁₂ mouse myoblasts and in the mouse embryo. Cx43 is highly abundant in undifferentiated myoblasts, but no Cx39 protein was detected in these cells. Upon differentiation into myotubes, Cx39 expression increased. The consecutive expression of these connexins was also observed in the mouse embryo. Cx39 and Cx43 were found in different plaques in accordance with the notion that Cx43 is exclusively expressed in myoblasts and Cx39 in myotubes. Thus, differentiating C₂C₁₂ cells in culture can serve to study the involvement of gap junctions in myogenesis, since expression of corresponding Cx39 and Cx43 proteins appears to be very similar as in the mouse embryo.