Fig. 1. Generation of Dermo1-cre mice and tissue-specific activity of the Dermo1-CRE recombinase. (A) A schematic representation of the Dermo1 genomic locus, the targeting vector and the mutant allele generated following homologous recombination. The arrow represents the cre gene and its transcriptional orientation. The length of diagnostic XhoI and EcoRV genomic restriction fragments are indicated by solid lines. Locations of the probes (5' and 3') used for DNA blot analysis and the primers (D1 and D2) used for PCR genotyping are indicated by filled boxes and arrowheads, respectively. FRT-neo contains a PGK-neo cassette (gray bar) flanked by flip recombination sites (black bar). (B) DNA blot analysis of XhoI-digested genomic DNA from embryonic stem cells hybridized with the 5' probe. (C) DNA blot analysis of EcoRV-digested tail DNA hybridized with the 3' probe. (D) Whole-mount detection of ß-gal activity in an E11.5 embryo. Note that neural tissue is not stained. (E) Frozen sagittal section of an E15.5 embryo stained for ß-gal activity. (F) Paraffin wax section of an E11.5 forelimb bud from the embryo shown in D. Note that the ectodermal epithelium is negative and the mesenchymal condensations (mc) are positive for ß-gal activity. (G) Frozen section of an E16.5 femur. The perichondrium and periosteum (arrows) are uniformly stained for ß-gal activity. (I,J,L) Frozen section of adult tibia, showing ß-gal activity in the growth plate (I), cortical bone (J) and osteoblasts lining bone trabecula (L). Bone marrow and muscle are not stained; F,G,I,J,L are counterstained with Nuclear Fast Red. Note that there are small clusters of unlabeled chondrocytes (^*) in the growth plate (G,I). (H,K) In situ hybridization detection of Fgfr2 expression in developing bone using a probe that detects the tyrosine kinase domain. (H) E16.5 femur. (K) The diaphysis of a P7 femur. Note Fgfr2 expression in diaphyseal lacunae (arrowhead). Bs, BspEI; C, ClaI; E, EcoRI; H, HindIII; N, NotI; Rv, EcoRV; Xh, XhoI. bm, bone marrow; cb, cortical bone; h, hypertrophic zone; mc, mesenchymal condensation; ob, osteoblast; oc, osteoclast; p, proliferation zone; tb, trabecular bone.