SMAD4 and colorectal carcinoma: Examples include mouse models of CRC with haploinsufficiency of Tgfbr2, Smad4, and intercrosses between Smad3/4 with the adaptor Sptbn1 (Tgfbr2−/−, Smad4+/−Sptbn1+/−, and Smad3+/−Sptbn1+/− on a C57BL/6 background) (17, 18, 22, 23).