title: The Dmp1-SOST Transgene Interacts With and Downregulates the Dmp1-Cre Transgene and the Rosa(Notch) Allele.
abstract: Activation of Notch1 in osteocytes of Rosa(Notch) mice, where a loxP-flanked STOP cassette and the Nicd coding sequence were targeted to the reverse orientation splice acceptor (Rosa)26 locus, causes osteopetrosis associated with suppressed Sost expression and enhanced Wnt signaling. To determine whether Sost downregulation mediates the effects of Notch activation in osteocytes, Rosa(Notch) mice were crossed with transgenics expressing Cre recombinase or SOST under the control of the dentin matrix protein (Dmp)1 promoter. Dmp1-SOST transgenics displayed vertebral osteopenia and a modest femoral cancellous and cortical bone phenotype, whereas hemizygous Dmp1-Cre transgenics heterozygous for the Rosa(Notch) allele (Dmp1-Cre;Rosa(Notch)) exhibited osteopetrosis. The phenotype of Notch activation in osteocytes was prevented in Dmp1-Cre;Rosa(Notch) mice hemizygous for the Dmp1-SOST transgene. The effect was associated with downregulated Notch signaling and suppressed Dmp1 and Rosa26 expression. To test whether SOST regulates Notch expression in osteocytes, cortical bone cultures from Dmp1-Cre;Rosa(Notch) mice or from Rosa(Notch) control littermates were exposed to recombinant human SOST. The addition of SOST had only modest effects on Notch target gene mRNA levels and suppressed Dmp1, but not Cre or Rosa26, expression. These findings suggest that prevention of the Dmp1-Cre;Rosa(Notch) skeletal phenotype by Dmp1-SOST is not secondary to SOST expression but to interactions among the Dmp1-SOST and Dmp1-Cre transgenes and the Rosa26 locus. In conclusion, the Dmp1-SOST transgene suppresses the expression of the Dmp1-Cre transgene and of Rosa26.
authors.affiliation: Departments of Orthopaedic Surgery and Medicine, and The UConn Musculoskeletal Institute, UConn Health, Farmington, 06030, Connecticut.
authors.forename: Stefano
authors.initials: S
authors.lastname: Zanotti
authors.affiliation: Departments of Orthopaedic Surgery and Medicine, and The UConn Musculoskeletal Institute, UConn Health, Farmington, 06030, Connecticut.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Canalis
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000483:Alleles; D000818:Animals; D001851:Bone Diseases, Metabolic / Q000235:genetics / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics* / Q000378:metabolism; D005269:Femur / Q000378:metabolism / Q000473:pathology; D015870:Gene Expression; D006023:Glycoproteins / Q000235:genetics* / Q000378:metabolism; D019426:Integrases / Q000235:genetics* / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010011:Osteocytes / Q000166:cytology / Q000378:metabolism; D010022:Osteopetrosis / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D022661:RNA, Untranslated / Q000235:genetics; D051881:Receptor, Notch1 / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019076:Transgenes / Q000235:genetics; D055114:X-Ray Microtomography
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C513308:Dmp1 protein, mouse; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; C110853:Gt(ROSA)26Sor non-coding RNA, mouse; D036341:Intercellular Signaling Peptides and Proteins; D022661:RNA, Untranslated; D051881:Receptor, Notch1; C486030:Sost protein, mouse; C045073:Cre recombinase; D019426:Integrases
keywords: BONE REMODELING; Cre RECOMBINASE; Dmp1; OSTEOCYTES; ROSA26 LOCUS; SOST