Many amino acid substitutions in, or near, this region exhibit different effects, for example I64N, T66I, G268C, D286G, and D291V in human skeletal actin ACTA1 exhibited reduced or completely lost polymerization capability, and resulted in various congenital myopathies (Feng and Marston, 2009). Here, ACTA1 is linked to congenital myopathy.