Fig. 5.
Knockout of floxed Casr in osteoblasts by OSX-Cre results in retarded growth and altered gene expression. (A) PCR analyses of genomic DNAs confirmed that deletion of exon 7 occurred only in bone from homozygous Osx-BoneCasrΔflox/Δflox (OSX-KO) mice and not in other tissues. (B) One-month-old OSX-KO mice were growth-retarded compared with control mice. (C) μCT images of trabecular (Tb) and cortical (Ct) bones in the distal femur and TFJ, respectively, showed severely under-mineralized matrix in 4-week-old KO mice compared with that in control mice. Scale bars: 1 mm for all panels. (D) μCT parameters assessed included BV, BV/TV, Th,N,CD, and SpforTbbone and TV, BV, and Th for Ct bone in 4-week-old control and OSX-KO mice. (*P < 0.01; n = 6 for KO and n = 12 for control mice). (E) Analysis of gene expression by qPCR in samples isolated from humeral cortices (no marrow) of newborn mice indicated delayed differentiation of osteoblasts in OSX-KO mice compared with that of control mice, with 55% reduced expression of Col(I) and 35% reduced expression of OCN. Results are presented as the percentage of L19 expression (*P < 0.05, n = 4 to 6 mice).