Molecular Biology of CCM

Cerebral cavernous malformations (CCMs) are slow-flow neurovascular anomalies of the central nervous system characterized by collections of enlarged and structurally irregular capillaries which exhibit dilated, thin and leaky walls. CCMs can occur either sporadically or as a familial autosomal disorder caused by a germline mutation with variable clinical and neuroradiological penetrance. Despite similar neurological manifestations, prevalence of patients harboring multiple cavernous malformations is much higher in the inherited form. Familial CCMs in humans result from loss-of-function mutations in any one of the three CCM genes encoding KRIT1 (also known as CCM1), CCM2 (also known as MGC4607 or malcaverin), or PDCD10 (also known as CCM3). The proteins encoded by the CCM genes are partly co-localized in a trimeric complex involved in number of partially interconnected signaling pathways controlling endothelial permeability and angiogenesis. Additionally, each of the CCM proteins have their own biological roles in a range of basic cellular processes including apoptosis, migration, polarization, and cell adhesion. Mutations in PDCD10 tend to result in a more aggressive form of the disease than those in KRIT1 or CCM2 suggesting potential differences in the signaling pathways in which PDCD10 is involved. No doubt the discovery of the CCM protein architectures has been invaluable towards the understanding of the CCM biology. However, to gain deeper insight into their cellular functions, interaction patterns, and cross-talks, further studies are necessary.