title: Notch1 signaling regulates chondrogenic lineage determination through Sox9 activation.
abstract: Notch signaling is involved in several cell lineage determination processes during embryonic development. Recently, we have shown that Sox9 is most likely a primary target gene of Notch1 signaling in embryonic stem cells (ESCs). By using our in vitro differentiation protocol for chondrogenesis from ESCs through embryoid bodies (EBs) together with our tamoxifen-inducible system to activate Notch1, we analyzed the function of Notch signaling and its induction of Sox9 during EB differentiation towards the chondrogenic lineage. Temporary activation of Notch1 during early stages of EB, when lineage determination occurs, was accompanied by rapid and transient Sox9 upregulation and resulted in induction of chondrogenic differentiation during later stages of EB cultivation. Using siRNA targeting Sox9, we knocked down and adjusted this early Notch1-induced Sox9 expression peak to non-induced levels, which led to reversion of Notch1-induced chondrogenic differentiation. In contrast, continuous Notch1 activation during EB cultivation resulted in complete inhibition of chondrogenic differentiation. Furthermore, a reduction and delay of cardiac differentiation observed in EBs after early Notch1 activation was not reversed by siRNA-mediated Sox9 knockdown. Our data indicate that Notch1 signaling has an important role during early stages of chondrogenic lineage determination by regulation of Sox9 expression.
authors.affiliation: Department of Virology and Cell Biology, University of Lübeck, Ratzeburger Allee 160, Lübeck, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Haller
authors.forename: R
authors.initials: R
authors.lastname: Schwanbeck
authors.forename: S
authors.initials: S
authors.lastname: Martini
authors.forename: K
authors.initials: K
authors.lastname: Bernoth
authors.forename: J
authors.initials: J
authors.lastname: Kramer
authors.forename: U
authors.initials: U
authors.lastname: Just
authors.forename: J
authors.initials: J
authors.lastname: Rohwedel
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D020219:Chondrogenesis / Q000187:drug effects / Q000502:physiology*; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism*; D004965:Estrogen Antagonists / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D006801:Humans; D051379:Mice; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D055758:SOX9 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013629:Tamoxifen / Q000494:pharmacology
chemical_list: D004965:Estrogen Antagonists; C497761:NOTCH1 protein, human; C497762:Notch1 protein, mouse; D051881:Receptor, Notch1; D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; C527933:Sox9 protein, mouse; D013629:Tamoxifen