KLF4 and cerebral cavernous malformation: To establish ERK5‐mediated KLF4 upregulation and KLF4‐dependent EndMT as common molecular nodes in CCM, we analyzed ERK5 activation, KLF4 amount, and EndMT marker expression in WT, CCM2 KO, or CCM3 KO ECs treated with XMD8‐92 or vehicle as control.