beta 1 integrin expression during normal and low score normal avian myogenesis

Skeletal muscle development is, in part, regulated by myoblast-extracellula r matrix interactions mediated by the transmembrane integrin family of hete rodimeric receptors. The avian genetic muscle weakness, low score normal (L SN), exhibits modified myotube and sarcomere structure that may be associat ed with altered integrin expression. Protein expression of the beta 1 integ rin subunit was measured during normal and LSN Pectoralis major muscle deve lopment at 14, 16, and 18 d of embryonic development, and 1 d and 1 and 6 w k posthatch. During embryonic development, integrin expression was downregu lated. However, by 1 wk posthatch, integrin levels were upregulated and rem ained elevated. through 6 wk posthatch. This pattern was observed in both n ormal and LSN muscle development. Overall, beta 1 integrin levels were lowe r in the LSN P. major muscle. In normal and LSN satellite cell cultures, be ta 1 integrin expression was low during proliferation. In early differentia tion, beta 1 integrin expression increased and was then downregulated. As o bserved in the muscle extracts, LSN beta 1 integrin expression was signific antly lower during differentiation. These results suggest that the regulati on of beta 1 integrin expression is critical to the progression of myogenes is, and, during LSN myogenesis, decreased expression of pi integrin may be associated with modifications in muscle structure.