Fibre type-specific and nerve-dependent regulation of myosin light chain 1 slow promoter in regenerating muscle

The regulation of a slow muscle gene, the myosinlight chain 1 slow/ventricular gene, has been studied by in vivotransfection into regenerating rat skeletal muscle. Constructscontaining portions of the myosin light chain 1 slow/ventricularpromoter linked to reporter genes were injected into fast andslow muscles 3 days after muscle injury by bupivacaine injection,and reporter gene activity was analysed after 10 days. We reportthat a sequence in the 5′ flanking region of the myosinlight chain 1 slow/ventricular gene is able to direct slowmuscle-specific regulation of reporter genes, and that theexpression of the transgene, like that of the correspondingendogenous gene, is dependent on intact nerve. This studyvalidates the use of regenerating muscle as a model for studyingmuscle gene regulation and is the first demonstration of a myosingene promoter regulated by nerve activity