Actin, alpha, skeletal muscle 1 (ACTA1) gene encodes skeletal muscle alpha-actin, which is the predominant actin isoform in the sarcomeric thin filaments of adult skeletal muscle, and essential, along with myosin, for muscle contraction. 1 Actin alpha 1 which is expressed in skeletal muscle is one of six different actin isoforms which have been identified. Actins are highly conserved proteins that are involved in cell motility, structure and integrity. Alpha actins are a major constituent of the contractile apparatus. 2 Alpha-skeletal actin can activate a regulatory pathway linking a subset of muscle genes that operates independently of normal differentiation and withdrawal from the cell cycle. 3