Although no cardiovascular malformations were observed in the identified AOS patients carrying heterozygous gain-of-function mutations in the CdGAP gene33, 34, 46, our results demonstrate here that the complete loss of CdGAP expression in mouse embryos leads to hypovascularization, vascular defects and incomplete embryonic/perinatal lethality. The gene discussed is ARHGAP31; the disease is Adams-Oliver syndrome.