Smad5 is efficiently deleted inMxCre;Smad5^fl/flconditional knockout mice. (A) Representative figure of a PCR screening of individual hematopoietic colonies from induced and uninduced MxCre;Smad5^fl/fl and wt mice. The primer pairs 1 and 2 and 1 and 3 were used to detect wt (235 bp), floxed (349 bp), and excised (387 bp) alleles, respectively, as previously described.¹⁷  Lane 1 shows DNA from an uninduced Smad5^fl/+ mouse lacking Cre (identical bands when induced; not shown); lanes 2 and 3, DNA from 2 different uninduced MxCre;Smad5^fl/fl mice; lanes 4 through 9, colony DNA from the same MxCre;Smad5^fl/fl mice after induction of Cre recombination (3 representative colonies/mouse); and lane 10, negative control. Exon 2 was deleted in more than 98% of all colonies tested (n = 446). (B) Western blot analysis of Smad5 protein in CD45⁺ BM cells from 3 different induced MxCre;Smad5^fl/fl and wt mice, demonstrating the lack of Smad5 protein in Cre-recombined cells. Actin was used as loading control.