Loss of LMOD1 impairs smooth muscle cytocontractility and causes megacystis microcolon intestinal hypoperistalsis syndrome in humans and mice

Proc Natl Acad Sci U S A. 2017 Mar 28;114(13):E2739-E2747. doi: 10.1073/pnas.1620507114. Epub 2017 Mar 14.


Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a congenital visceral myopathy characterized by severe dilation of the urinary bladder and defective intestinal motility. The genetic basis of MMIHS has been ascribed to spontaneous and autosomal dominant mutations in actin gamma 2 (ACTG2), a smooth muscle contractile gene. However, evidence suggesting a recessive origin of the disease also exists. Using combined homozygosity mapping and whole exome sequencing, a genetically isolated family was found to carry a premature termination codon in Leiomodin1 (LMOD1), a gene preferentially expressed in vascular and visceral smooth muscle cells. Parents heterozygous for the mutation exhibited no abnormalities, but a child homozygous for the premature termination codon displayed symptoms consistent with MMIHS. We used CRISPR-Cas9 (CRISPR-associated protein) genome editing of Lmod1 to generate a similar premature termination codon. Mice homozygous for the mutation showed loss of LMOD1 protein and pathology consistent with MMIHS, including late gestation expansion of the bladder, hydronephrosis, and rapid demise after parturition. Loss of LMOD1 resulted in a reduction of filamentous actin, elongated cytoskeletal dense bodies, and impaired intestinal smooth muscle contractility. These results define LMOD1 as a disease gene for MMIHS and suggest its role in establishing normal smooth muscle cytoskeletal-contractile coupling.

Keywords: CRISPR-Cas9; Leiomodin; genetics; myopathy; smooth muscle.

Publication types

  • Case Reports
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abnormalities, Multiple / genetics*
  • Animals
  • Autoantigens / genetics
  • Autoantigens / metabolism
  • Autoantigens / physiology*
  • Codon, Nonsense
  • Colon / abnormalities*
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism
  • Cytoskeletal Proteins / physiology*
  • Female
  • Humans
  • Infant, Newborn
  • Intestinal Pseudo-Obstruction / genetics*
  • Mice
  • Muscle Contraction / genetics
  • Muscle Proteins / genetics
  • Muscle Proteins / metabolism
  • Muscle Proteins / physiology*
  • Muscle, Smooth / physiology
  • Urinary Bladder / abnormalities*


  • Autoantigens
  • Codon, Nonsense
  • Cytoskeletal Proteins
  • LMOD1 protein, human
  • Muscle Proteins
  • leiomodin protein, mouse

Supplementary concepts

  • Megacystis microcolon intestinal hypoperistalsis syndrome