Fig. 1.

(A) Schematic diagram of the experimental design. To induce recombination of the floxed βcat alleles in fully adult mice, tamoxifen (Tam) was first injected at 17 wks of age, then several times thereafter to ensure recombination. Numbers in parentheses indicate days between manipulations. (B) To assess βcat expression in bone and muscle after tamoxifen-induced Cre translocation, RNA from cortical bone and muscle were collected by laser capturing technique from frozen sections. Moving from left to right, the panels show a portion of the femur cortex with the laser ROI indicated by the dashed box (left), the section midway through the laser capture process (middle), and the section after the defined cortical bone region had dropped into the cap (right) for analysis. Original lens magnification is 10X. (C) Real time PCR revealed a significant tamoxifen-induced reduction in βcat expression in the laser captured fragments in both Cre genotypes (* p < 0.05 compared to CreERt2− with Oil group, + p < 0.05 compared to CreERt2− with tamoxifen group, # p < 0.05 compared to CreERt2+ with Oil group) and a roughly 50% reduction in βcat expression among CreERt2+ mice that were not exposed to tamoxifen. (D) βcat expression in muscle fragments was fairly consistent across genotype/treatment (with the exception of tamoxifen-treated CreERt2− mice) groups, indicating a lack of Cre nuclear activity in muscle tissue with this model. Sample size is n=10/group.