Developmental regulation of M‐cadherin in the terminal differentiation of skeletal myoblasts

Abstract

Cadherins form a large family of membrane glycoproteins which mediate homophilic calcium‐dependent cell adhesion. They are thought to mediate the initial calcium‐dependent cell adhesion which precedes the plasma membrane fusion of skeletal myoblasts. Two cadherin subtypes are known to be expressed in mammalian skeletal myoblasts: muscle cadherin (M‐cadherin) and neural cadherin (N‐cadherin). In the present study we demonstrate that (1) the expression of M‐ and N‐cadherin is differentially regulated during myoblast differentiation in vitro, (2) the expression of M‐cadherin but not N‐cadherin is inhibited by 5‐bromo‐2′‐deoxyuridine (BUdR), an agent which selectively inhibits skeletal myoblast differentiation, and (3) fusion and differentiation‐competent rat L6 myoblasts do not express detectable levels of N‐cadherin mRNA. In vivo, M‐cadherin mRNA was detectable exclusively in skeletal muscle. M‐cadherin mRNA levels peaked during the secondary myogenic wave in rat hindlimb muscle, becoming barely detectable in 1‐week‐old and adult rats. These observations indicate that M‐cadherin is unique in two ways: It is the first cadherin to be included in the family of skeletal muscle‐specific genes, and its shows peak leels of expression in developing skeletal muscle tissue. Taken together, these results suggest that M‐cadherin plays an important role in skeletal myogenesis. © 1994 Wiley‐Liss, Inc. Copyright © 1994 Wiley‐Liss, Inc.