title: Analysis of SOST expression using large minigenes reveals the MEF2C binding site in the evolutionarily conserved region (ECR5) enhancer mediates forskolin, but not 1,25-dihydroxyvitamin D3or TGFβ1responsiveness.
abstract: Transcribed from the SOST gene, sclerostin is an osteocyte-derived negative regulator of bone formation that inhibits osteoblastogenesis via antagonism of the Wnt pathway. Sclerostin is a promising therapeutic target for low bone mass diseases and neutralizing antibody therapies that target sclerostin are in development. Diverse stimuli regulate SOST including the vitamin D hormone, forskolin (Fsk), bone morphogenic protein 2 (BMP-2), oncostatin M (OSM), dexamethasone (Dex), and transforming growth factor (TGFβ1). To explore the mechanisms by which these compounds regulate SOST expression, we examined their ability to regulate a SOST reporter minigene containing the entire SOST locus including the downstream regionor mutant minigenes containing a deletion of the -1kb to -2kb promoter proximal region (-1kb), ECR2, ECR5, or two point mutations in the MEF2 binding site of ECR5 (ECR5/MEF2). Previous reports suggest that both the PTH and TGFβ1effects on SOST are mediated through ECR5 and that the action of PTH is mediated specifically via the MEF2 binding site at ECR5. Consistent with these reports, the suppressive effects of Fsk were abrogated following both ECR5 deletion and ECR5/MEF2 mutation. In contrast, we found that TGFβ1negatively regulated SOST and that neither ECR5 nor ECR5/MEF2 was involved. Surprisingly, none of these four deletions/mutations abrogated the suppressive effects of the vitamin D hormone, OSM, Dex, or TGFβ1, or the positive effects of BMP-2. These data suggest that we need to move beyond ECR5 to understand SOST regulation.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, United States.
authors.forename: Hillary C
authors.initials: HC
authors.lastname: St John
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, United States.
authors.forename: Sydney J
authors.initials: SJ
authors.lastname: Hansen
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, United States. Electronic address: pike@biochem.wisc.edu.
authors.forename: J Wesley
authors.initials: JW
authors.lastname: Pike
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics / Q000378:metabolism; D002117:Calcitriol / Q000494:pharmacology; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology*; D017124:Conserved Sequence; D003907:Dexamethasone / Q000494:pharmacology; D004742:Enhancer Elements, Genetic; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D064326:MEF2 Transcription Factors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D053683:Oncostatin M / Q000494:pharmacology; D011485:Protein Binding; D053773:Transforming Growth Factor beta1 / Q000235:genetics* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D064326:MEF2 Transcription Factors; C578041:Mef2c protein, mouse; C486030:Sost protein, mouse; D053773:Transforming Growth Factor beta1; D053683:Oncostatin M; D005576:Colforsin; D003907:Dexamethasone; D002117:Calcitriol
keywords: BAC; ECR5; MEF2C; Osteocyte; SOST