FIG. 2.

PTK6 expression in the small and large intestines. A. PTK6 protein expression is highest in the neonatal colon and adult ileum. Immunoblotting was performed to examine PTK6 protein expression in wild-type and Ptk6^−/− small and large intestines. Lysates from three wild-type and three Ptk6^−/− neonatal (14-day-old) and adult (8-week-old) animals were probed with anti-mouse PTK6 (Sik) antibodies. No PTK6 was detected in the Ptk6^−/− lysates. As a control, blots were also probed with antibodies specific for β-actin. B. PTK6 is expressed in nondividing differentiated cells of the small intestine and colon. The boxed region is magnified, and the arrows denote cells with reduced immunoreactivity in the villus epithelium of the jejunum. The colon lacks villi (V), and differentiation and cell cycle exit occur in the upper regions of the crypt (C). Immunohistochemistry was performed with adult wild-type jejunum and colon, using anti-PTK6 antibodies or anti-rabbit immunoglobulin G (IgG) antibodies as controls and DAB as a substrate (brown). Bar, 50 μm.