Transcription of the embryonic myosin light chain gene is restricted to type II muscle fibers in human adult masseter

Abstract

We have previously demonstrated that the embryonic myosin light chain (MLC1emb) isoform whose expression is restricted to the early fetal stages in most mammalian skeletal muscles, persists throughout development in human masseter muscle. In order to go further in this study, we have compared the developmental profile of MLC1emb gene transcription in human masseter and quadriceps muscles using both Northern blotting and in situ hybridization techniques. Interestingly, whereas expression of this gene was observed in all fibers during fetal stages in both muscles, transcription in adult masseter was found to be restricted to type II fibers. Existence of a masseter-specific pathway of muscle gene regulation is discussed.