CDON and holoprosencephaly: Other down-regulated genes encoding adhesion molecules were: Jam3, a tight-junction protein essential for maintaining the integrity of the cerebrovascular endothelium [116]; Cdh6, which is expressed in the VZ where it may serve to assign the cortico-striatal boundary [117]; two additional IGSFM genes, Boc and Cdon, that are evident in the VZ, where they function in Sonic Hedgehog signaling and are implicated in forms of holoprosencephaly [118,119].