title: 1α,25-dihydroxyvitamin D3 stimulates human SOST gene expression and sclerostin secretion.
abstract: Sclerostin, the SOST gene product, is a negative regulator of bone formation and a positive regulator of bone resorption. In this study, treatment of human primary osteoblasts, including cells differentiated to an osteocyte-like stage, with 1α,25-dihydroxyvitaminD3 (1,25D) resulted in the dose-dependent increased expression of SOST mRNA. A similar effect was observed in human trabecular bone samples cultured ex vivo, and in osteocyte-like cultures of differentiated SAOS2 cells. Treatment of SAOS2 cells with 1,25D resulted in the production and secretion of sclerostin protein. In silico analysis of the human SOST gene revealed a single putative DR3-type vitamin D response element (VDRE) at position -6216 bp upstream of the transcription start site (TSS). This sequence was confirmed to have strong VDRE activity by luciferase reporter assays and electrophoretic mobility shift analysis (EMSA). Sequence substitution in the VDR/RXR half-sites abolished VDRE reporter activity and binding of nuclear proteins. A 6.3 kb fragment of the human proximal SOST promoter demonstrated responsiveness to 1,25D. The addition of the evolutionary conserved region 5 (ECR5), a known bone specific enhancer region, ahead of the 6.3 kb fragment increased basal promoter activity but did not increase 1,25D responsiveness. Site-specific mutagenesis abolished the responsiveness of the 6.3 kb promoter to 1,25D. We conclude that 1,25D is a direct regulator of human SOST gene and sclerostin protein expression, extending the pathways of control of sclerostin expression. At least some of this responsiveness is mediated by the identified classical VDRE however the nature of the transcriptional regulation by 1,25D warrants further investigation.
authors.affiliation: Centre for Orthopaedic and Trauma Research, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: Asiri R
authors.initials: AR
authors.lastname: Wijenayaka
authors.affiliation: Centre for Orthopaedic and Trauma Research, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: Dongqing
authors.initials: D
authors.lastname: Yang
authors.affiliation: Centre for Orthopaedic and Trauma Research, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: Matthew
authors.initials: M
authors.lastname: Prideaux
authors.affiliation: Centre for Orthopaedic and Trauma Research, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Ito
authors.affiliation: Centre for Orthopaedic and Trauma Research, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Kogawa
authors.affiliation: School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia 5001, Australia.
authors.forename: Paul H
authors.initials: PH
authors.lastname: Anderson
authors.affiliation: School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, South Australia 5001, Australia.
authors.forename: Howard A
authors.initials: HA
authors.lastname: Morris
authors.affiliation: Centre for Orthopaedic and Trauma Research, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: Lucian B
authors.initials: LB
authors.lastname: Solomon
authors.affiliation: Lawrence Livermore National Laboratories, Physical and Life Sciences Directorate, Livermore, CA, USA; University of California at Merced, School of Natural Sciences, Merced, CA, USA.
authors.forename: Gabriela G
authors.initials: GG
authors.lastname: Loots
authors.affiliation: Centre for Orthopaedic and Trauma Research, University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: David M
authors.initials: DM
authors.lastname: Findlay
authors.affiliation: Centre for Orthopaedic and Trauma Research, University of Adelaide, Adelaide, South Australia 5005, Australia. Electronic address: gerald.atkins@adelaide.edu.au.
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Atkins
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D002117:Calcitriol / Q000494:pharmacology*; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000502:physiology; D005819:Genetic Markers / Q000235:genetics; D006801:Humans; D010011:Osteocytes / Q000166:cytology / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects* / Q000502:physiology; D030181:Vitamin D Response Element / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019485:Bone Morphogenetic Proteins; D005819:Genetic Markers; C422903:SOST protein, human; D002117:Calcitriol
keywords: Gene regulation; Osteocyte; Promoter; SOST; Sclerostin; Vitamin D; Vitamin D response element