title: Expression and function of Dlx genes in the osteoblast lineage.
abstract: Our laboratory and others have shown that overexpression of Dlx5 stimulates osteoblast differentiation. Dlx5(-/-)/Dlx6(-/-) mice have more severe craniofacial and limb defects than Dlx5(-/-), some of which are potentially due to defects in osteoblast maturation. We wished to investigate the degree to which other Dlx genes compensate for the lack of Dlx5, thus allowing normal development of the majority of skeletal elements in Dlx5(-/-) mice. Dlx gene expression in cells from different stages of the osteoblast lineage isolated by FACS sorting showed that Dlx2, Dlx5 and Dlx6 are expressed most strongly in less mature osteoblasts, whereas Dlx3 is very highly expressed in differentiated osteoblasts and osteocytes. In situ hybridization and Northern blot analysis demonstrated the presence of endogenous Dlx3 mRNA within osteoblasts and osteocytes. Dlx3 strongly upregulates osteoblastic markers with a potency comparable to Dlx5. Cloned chick or mouse Dlx6 showed stimulatory effects on osteoblast differentiation. Our results suggest that Dlx2 and Dlx6 have the potential to stimulate osteoblastic differentiation and may compensate for the absence of Dlx5 to produce relatively normal osteoblastic differentiation in Dlx5 knockout mice, while Dlx3 may play a distinct role in late stage osteoblast differentiation and osteocyte function.
authors.affiliation: Department of Genetics and Developmental Biology, University of Connecticut Health Center, 263 Farmington Avenue, CT 06030, USA.
authors.forename: Haitao
authors.initials: H
authors.lastname: Li
authors.forename: Inga
authors.initials: I
authors.lastname: Marijanovic
authors.forename: Mark S
authors.initials: MS
authors.lastname: Kronenberg
authors.forename: Ivana
authors.initials: I
authors.lastname: Erceg
authors.forename: Mary Louise
authors.initials: ML
authors.lastname: Stover
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Velonis
authors.forename: Mina
authors.initials: M
authors.lastname: Mina
authors.forename: Jelica Gluhak
authors.initials: JG
authors.lastname: Heinrich
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Harris
authors.forename: William B
authors.initials: WB
authors.lastname: Upholt
authors.forename: Ivo
authors.initials: I
authors.lastname: Kalajzic
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Lichtler
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001854:Bone Marrow Cells / Q000166:cytology / Q000502:physiology; D002454:Cell Differentiation; D003001:Cloning, Molecular; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000235:genetics*; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology*; D010011:Osteocytes / Q000166:cytology / Q000502:physiology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D017154:Stromal Cells / Q000166:cytology / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics*
chemical_list: C088334:Distal-less homeobox proteins; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D014157:Transcription Factors