β1 Integrin Expression During Normal and Low Score Normal Avian Myogenesis1

ABSTRACT Skeletal muscle development is, in part, regulated by myoblast-extracellular matrix interactions mediated by the transmembrane integrin family of heter-odimeric 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 β1 integrin subunit was measured during normal and LSN Pectoralis major muscle development at 14, 16, and 18 d of embry-onic 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 throug