Apoptotic functions of PDCD10/CCM3, the gene mutated in cerebral cavernous malformation 3

Background and Purpose - Mutations in the Programmed Cell Death 10 (PDCD10) gene cause autosomal dominant familial cerebral cavernous malformations (CCM3). To date, little is known about the function of this gene and its role in disease pathogenesis. Methods - We examined the effects of overexpression of wild-type and 2 human disease-causing variants of PDCD10 on cell death using 3 different methods (TUNEL and MTT assays and caspase-3 activation). We analyzed expression of CCM3, activated caspase-3, and p38 in endothelial cell lines using the serum deprivation model of apoptosis induction. Finally, we assayed the effects of siRNA-mediated inhibition of endogenous PDCD10 expression on cell death in endothelial cell cultures. Results - Overexpression of wild-type CCM3, but not disease-linked mutant forms, induced apoptosis as confirmed by TUNEL and increased levels of activated caspase-3. Serum starvation of endothelial cells, an inducer of apoptosis, led to increased expression of CCM3 and activation of p38 and ultimately activated caspase-3. siRNA-mediated inhibition of CCM3 expression resulted in decreased levels of p38 and activated caspase-3, and decreased cell death. Conclusions - CCM3 is both necessary and sufficient to induce apoptosis in vitro in well-defined cell culture systems. Even though it is currently unclear whether this effect on apoptosis is direct or indirect through modulation of cell cycle, these results led to the novel hypothesis that CCM lesions may form as a consequence of aberrant apoptosis, potentially altering the balance between the endothelium and neural cells within the neurovascular unit.