PITX2 and coloboma: Mice heterozygous for Pitx2 display multiple anterior segment defects similar to ARS, including corneal endoderm and iris stroma agenesis, corneal mesothelial thickening, coloboma formation, and shortened ventral retina, and Pitx2−/− mice are embryonic lethal due to incomplete closure of the ventral body wall [46, 47].