Beta1 integrin expression during normal and low score normal avian myogenesis.

Skeletal muscle development is, in part, regulated by myoblast-extracellular matrix interactions mediated by the transmembrane integrin family of heterodimeric receptors. The avian genetic muscle weakness, low score normal (LSN), exhibits modified myotube and sarcomere structure that may be associated with altered integrin expression. Protein expression of the beta1 integrin subunit was measured during normal and LSN Pectoralis major muscle development at 14, 16, and 18 d of embryonic development, and 1 d and 1 and 6 wk posthatch. During embryonic development, integrin expression was downregulated. However, by 1 wk posthatch, integrin levels were upregulated and remained elevated through 6 wk posthatch. This pattern was observed in both normal and LSN muscle development. Overall, beta1 integrin levels were lower in the LSN P. major muscle. In normal and LSN satellite cell cultures, beta1 integrin expression was low during proliferation. In early differentiation, beta1 integrin expression increased and was then downregulated. As observed in the muscle extracts, LSN beta1 integrin expression was significantly lower during differentiation. These results suggest that the regulation of beta1 integrin expression is critical to the progression of myogenesis, and, during LSN myogenesis, decreased expression of beta1 integrin may be associated with modifications in muscle structure.