Figure 1.
Expression of Cre recombinase in Col3.6-Cre–transgenic mice. (A) PCR performed using Cre primers on reverse-transcribed RNA isolated from adult Col3.6-Cre–transgenic mice. Primers to GAPDH were used as a positive control in the RT-PCR, whereas non–reverse-transcribed (No RT) rib bone RNA, liver RNA, and water (H20) were used as negative controls for the PCR. Cre expression is readily detected in the rib and femur of these mice. (B) Whole-mount staining of lacZ expression in Col3.6-Cre–transgenic R26R embryos at E10, -12.5, and -15.5 during development. Expression of the Cre recombinase as detected by β-galactosidase activity is detected in surface ectoderm and in the caudal portion of the embryo at E10, with the highest levels found in the tail bud (arrow). Between E12.5 and -15.5, the Col3.6-Cre transgene undergoes robust activation with the formation of connective tissue. (C) Staining for β-galactosidase activity in sagital sections of R26R/Col3.6-Cre embryos indicates that Cre-mediated excision occurs in both the skin and developing skeletal elements at E12.5–14.5.