Arrows indicate IRSp53 and F-actin at the luminal side of the cyst. Scale bar, 18 µm. b Five days old 3D cysts of MDCK control cells (IRSp53 Ctr) or IRSp53-KO obtained by CRISPR/Cas9, or MDCK control (MDCK Ctr) or IRSp53-KD (not shown). Left: the cysts were stained ...