MYL3,also named as MLC1v,is an essential light chain of myosin that is associated with muscle contraction. It is expressed in ventricular and slow skeletal muscle. MYL3 may serve as a target for caspase-3 in dying cardiomyocytes. Mutations of MYL3 gene cause hypertrophic cardiomyopathy. MYL3 has been identified as potential serum biomarker for drug induced myotoxicity. Great increase in MYL3 serum concentration has been observed in rats with cardiac and skeletal muscle injury.