Fig. 1. TAM injection induces epithelium-specific inactivation of Apc all along the crypt-villus axis. (A) Structure of the conditionally targeted allele of Apc. Exons 11 to 15 are indicated as black bars. The positions of the primers used for the detection of each allele are indicated: 13F, 15R. In floxed mice, induction of Cre recombination by TAM injection induced exon 14 deletion, generating a frameshift mutation at codon 580 (appearance of the stop codon TAA). (B, left) Cre expression in the small intestine before (D0) and 2 days after (D2) TAM injection in mutant mice. (Middle) RT-PCR analyses on days 0 (D0), 2 (D2) and 4 (D4) in mutant mice reveal the floxed (Apc^lox) and deleted (Apc^ex14) Apc alleles. (Right) Immunostaining of APC on day 4 in control and mutant mice, showing loss of APC protein in the mutant mice.