title: Wdr5, a WD-40 protein, regulates osteoblast differentiation during embryonic bone development.
abstract: Wdr5 accelerates osteoblast and chondrocyte differentiation in vitro, and is developmentally expressed in osteoblasts as well as in proliferating and hypertrophic chondrocytes. To investigate the role of Wdr5 during endochondral bone development, transgenic mice overexpressing Wdr5 under the control of the 2.3-kb fragment of the mouse alpha(1) I collagen promoter were generated. The transgene was specifically expressed in the osteoblasts of transgene positive mice and was absent in the growth plate. Histological analyses at embryonic day 14.5 demonstrated that the humeri of transgene positive embryos were longer than those isolated from wild-type littermates largely due to an expansion of the hypertrophic chondrocyte layer. Acceleration of osteoblast differentiation was observed with greater and more extensive expression of type I collagen and more extensive mineral deposition in the bone collar of transgene positive embryos. Acceleration of vascular invasion was also observed in transgene positive mice. Postnatal analyses of transgenic mice confirmed persistent acceleration of osteoblast differentiation. Targeted expression of Wdr5 to osteoblasts resulted in earlier activation of the canonical Wnt signaling pathway in the bone collar as well as in primary calvarial osteoblast cultures. In addition, overexpression of Wdr5 increased the expression of OPG, a target of the canonical Wnt signaling pathway. Overall, our findings suggest that Wdr5 accelerates osteoblast differentiation in association with activation of the canonical Wnt pathway.
authors.affiliation: Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Francesca
authors.initials: F
authors.lastname: Gori
authors.forename: Lauren G
authors.initials: LG
authors.lastname: Friedman
authors.forename: Marie B
authors.initials: MB
authors.lastname: Demay
mesh_terms: D000818:Animals; D001846:Bone Development; D001842:Bone and Bones / Q000166:cytology / Q000196:embryology; D002454:Cell Differentiation; D019902:Chondrocytes / Q000473:pathology; D024042:Collagen Type I / Q000235:genetics; D004622:Embryo, Mammalian; D004627:Embryonic Induction; D006023:Glycoproteins / Q000235:genetics; D006811:Humerus; D015576:Hyperostosis / Q000473:pathology; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000166:cytology*; D053244:Osteoprotegerin; D011506:Proteins / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics; D051153:Wnt Proteins / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D053244:Osteoprotegerin; D011506:Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C506031:Tnfrsf11b protein, mouse; C443118:Wdr5 protein, mouse; D051153:Wnt Proteins