Oral-facial-digital type I protein is required for primary cilia formation and left-right axis specification.

The oral-facial-digital type I (OFD1) syndrome (OMIM 311200) is a human developmental disorder; affected individuals have craniofacial and digital abnormalities and, in 15% of cases, polycystic kidney. The disease is inherited as an X-linked dominant male-lethal trait. Using a Cre-loxP system, we generated knockout animals lacking Ofd1 and reproduced the main features of the disease, albeit with increased severity, possibly owing to differences of X inactivation patterns between human and mouse. We found failure of left-right axis specification in mutant male embryos, and ultrastructural analysis showed a lack of cilia in the embryonic node. Formation of cilia was defective in cystic kidneys from heterozygous females, implicating ciliogenesis as a mechanism underlying cyst development. In addition, we found impaired patterning of the neural tube and altered expression of the 5' Hoxa and Hoxd genes in the limb buds of mice lacking Ofd1, suggesting that Ofd1 could have a role beyond primary cilium organization and assembly.