Myosin light chain 3 synthesis during chick pectoralis muscle development in ovo.

The level of myosin light chain 3 (LC3) in vertebrate skeletal muscle is developmentally regulated in a tissue-specific manner. We have used the RNA-cDNA hybridization assay to quantitate LC3 mRNA levels at various stages of chick pectoralis muscle development in ovo. The LC3 mRNA was found significantly in breast muscle only on Day 16 in ovo and later, the level of mRNA ranging from about 30 to 32% of that present in adult tissue. These values are in good agreement with the corresponding levels of LC3 in embryonic muscle. These results do not support the earlier reports that the protein and mRNA for LC3 accumulate in a noncoordinate manner in embryonic pectoralis muscle and they suggest that LC3 synthesis in ovo is regulated primarily at the transcriptional level.