KRIT1 and cerebral cavernous malformation: Using CRISPR/Cas9 genome editing, we inactivated the CCM1 wild-type allele in CCM1+/− BOECs or induced biallelic frameshift variants in CCM1+/+ CI-huVECs and thereby generated pairs of CCM1+/− and CCM1−/− BOECs (hereditary CCM model) or CCM1+/+ and CCM1−/− CI-huVECs (sporadic CCM model), respectively.