MAPK3 and cervical squamous intraepithelial neoplasia: Indeed, the crypts of jejunum/ileum of the Mad2f/ −; Cre-ERT2 and Mad2f/f; p533f/f; Cre-ERT2 mice show many apoptotic cells (zoomed-in sections Fig. 2A), indicating that these cells indeed cope very poorly with CIN.