Global deletion of SM RLC can cause postnatal lethality in mice, with a similar phenotype as megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) patients who have homologous MYL9 mutations (Moreno et al., 2018). This evidence concerns the gene MYL9 and megacystis-microcolon-intestinal hypoperistalsis syndrome 1.