ACTN3 Gene and Skeletal Muscle.

The alpha-actinin is actin-binding protein. In skeletal muscle, alpha-actinins-2 (ACTN2) and alpha-actinins-3 (ACTN3) isoforms are playing an important role as structural component of the Z-lines that anchor the actin-containing thin filaments and maintain the spatial relationship between myofilaments. ACTN3 is expressed only in type II muscle fibers while the ACTN2 is found in all muscle fibers. A common nonsense mutation in ACTN3 (R577X) results in ACTN3 deficiency that appears to be non-pathogenic and it is postulated that ACTN2 compensates for the deficiency. Therefore, it is hypothesized that ACTN3 genotype (RR, RX, XX) may influence variation in muscle function in humans and many studies have confirmed that the presence of the ACTN3 protein, or RR genotype is associated with greater success in activities requiring sprint or power performance. In contrast to the findings in power athletes, it is controversial that a lack of ACTN3 protein, or XX genotype is beneficial to endurance athletes. And associations of ACTN3 genotype with trainability, exercise-induced muscle damage and age-related changes of muscular function have been studied. However, these results are different among the studies because of differences of human race, age, sex, and physical activity level and so on. To clarify roles of ACTN3 genotype on skeletal muscle functions and their mechanisms, further studies with genetically modified animal models would be useful. [ABSTRACT FROM AUTHOR]