This functional relationship explains the phenotypic similarities between Multisystemic Smooth Muscle Dysfunction Syndrome caused by ACTA2 mutations, and Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome 2 caused by MYH11 mutations. The gene discussed is MYH11; the disease is megacystis-microcolon-intestinal hypoperistalsis syndrome 2.