title: Transgenic mice for a tamoxifen-induced, conditional expression of the Cre recombinase in osteoclasts.
abstract: BACKGROUND
  Studies on osteoclasts, the bone resorbing cells, have remained limited due to the lack of transgenic mice allowing the conditional knockout of genes in osteoclasts at any time during development or adulthood.
  
  
  RESULTS
  We report here on the generation of transgenic mice which specifically express a tamoxifen-inducible Cre recombinase in osteoclasts. These mice, generated on C57BL/6 and FVB background, express a fusion Cre recombinase-ERT2 protein whose expression is driven by the promoter of cathepsin K (CtsK), a gene highly expressed in osteoclasts. We tested the cellular specificity of Cre activity in CtsKCreERT2 strains by breeding with Rosa26LacZ reporter mice. PCR and histological analyses of the CtsKCreERT2LacZ positive adult mice and E17.5 embryos show that Cre activity is restricted largely to bone tissue. In vitro, primary osteoclasts derived from the bone marrow of CtsKCreERT2+/-LacZ+/- adult mice show a Cre-dependent β-galactosidase activity after tamoxifen stimulation.
  
  
  CONCLUSIONS
  We have generated transgenic lines that enable the tamoxifen-induced, conditional deletion of loxP-flanked genes in osteoclasts, thus circumventing embryonic and postnatal gene lethality and avoiding gene deletion in other cell types. Such CtsKCreERT2 mice provide a convenient tool to study in vivo the different facets of osteoclast function in bone physiology during different developmental stages and adulthood of mice.
authors.affiliation: Biotechnology Center, Dresden University of Technology, Tatzberg, Dresden, Germany.
authors.forename: Maria Arantzazu
authors.initials: MA
authors.lastname: Sanchez-Fernandez
authors.forename: Silvia
authors.initials: S
authors.lastname: Sbacchi
authors.forename: Miguel
authors.initials: M
authors.lastname: Correa-Tapia
authors.forename: Ronald
authors.initials: R
authors.lastname: Naumann
authors.forename: Jennifer
authors.initials: J
authors.lastname: Klemm
authors.forename: Pierre
authors.initials: P
authors.lastname: Chambon
authors.forename: Samiya
authors.initials: S
authors.lastname: Al-Robaiy
authors.forename: Manfred
authors.initials: M
authors.lastname: Blessing
authors.forename: Bernard
authors.initials: B
authors.lastname: Hoflack
mesh_terms: D000818:Animals; D016723:Bone Remodeling / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006367:HeLa Cells; D006801:Humans; D019426:Integrases / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D023421:Models, Animal; D010010:Osteoclasts / Q000201:enzymology*; D013629:Tamoxifen / Q000494:pharmacology*; D014018:Tissue Distribution
chemical_list: D017931:DNA Primers; D013629:Tamoxifen; C045073:Cre recombinase; D019426:Integrases