KRIT1 and cerebrocostomandibular syndrome: Together, mutations in these genes account for over 85% of familial CCM syndromes, with Krit1/CCM1 and MGC4607/CCM2 accounting for the majority (each ~40%).[30] The current thought is that the CCM genes play a role in angiogenesis and vasculogenesis.[56] All three genes are expressed throughout the neuronal cell layers during development and adulthood as well as within the developing blood vessels by mid-gestation.[41] MGC4607/CCM2 and PDCD10/CCM3 in particular are robustly expressed within the meningeal and parenchymal cortical vessels post-natally.