Cadherins Promote Skeletal Muscle Differentiation in Three-dimensional Cultures

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Abstract
The cell–cell adhesion molecule N-cadherin, with its associated catenins, is expressed by differentiating skeletal muscle and its precursors. Although N-cadherin's role in later events of skeletal myogenesis such as adhesion during myoblast fusion is well established, less is known about its role in earlier events such as commitment and differentiation. Using an in vitro model system, we have determined that N-cadherin– mediated adhesion enhances skeletal muscle differentiation in three-dimensional cell aggregates. We transfected the cadherin-negative BHK fibroblastlike cell line with N-cadherin. Expression of exogenous N-cadherin upregulated endogenous β-catenin and induced strong cell–cell adhesion. When BHK cells were cultured as three-dimensional aggregates, N-cadherin enhanced withdrawal from the cell cycle and stimulated differentiation into skeletal muscle as measured by increased expression of sarcomeric myosin and the 12/101 antigen. In contrast, N-cadherin did not stimulate differentiation of BHK cells in monolayer cultures. The effect of N-cadherin was not unique since E-cadherin also increased the level of sarcomeric myosin in BHK aggregates. However, a nonfunctional mutant N-cadherin that increased the level of β-catenin failed to promote skeletal muscle differentiation suggesting an adhesion-competent cadherin is required. Our results suggest that cadherin-mediated cell–cell interactions during embryogenesis can dramatically influence skeletal myogenesis.