CTNNB1 and adenoma: The most extensive intestinal hyperproliferation and adenoma formation resulted from Cre-mediated excision of exon 3 (encoding amino acids 5-80) of the endogenous ctnnb1 gene throughout the intestinal mucosa, thereby deleting all the regulatory serine and threonine residues that control the turnover of the β-catenin protein (Harada et al., 1999; Leedham et al., 2013).