These differences in spatial and temporal expression are considered explanations for the exclusive association of skeletal muscle abnormalities (i.e., nemaline myopathy [MIM: 161800], actin accumulation myopathy [MIM: 161800], congenital fiber-type disproportion [MIM: 255310], intranuclear rod myopathy [MIM: 161800], etc.)with pathogenic ACTA1 variants and cardiac abnormalities (autosomal dominant atrial septal defects [MIM: 612794],44 dilated [MIM: 613424]45 and hypertrophic [MIM: 612098]46 cardiomyopathy, and left ventricular noncompaction [MIM: 613424]47) with pathogenic variants in ACTC1. The gene discussed is ACTC1; the disease is left ventricular noncompaction.