title: Segmental border is defined by Ripply2-mediated Tbx6 repression independent of Mesp2.
abstract: The precise border of somites formed during mouse somitogenesis is defined by a Tbx6 expression domain, which is established by Mesp2-mediated Tbx6 suppression in the anterior part of the presomitic mesoderm (PSM). Ripply2, a target of Mesp2, is proposed to be involved in this down-regulation because Ripply2 deficiency causes an anterior expansion of the Tbx6 domain, resembling the Mesp2-null phenotype. However, it is unclear whether Ripply2 acts on Tbx6 independently or in association with Mesp2. To address this question, we generated three sets of transgenic mice with the following Ripply2 expression patterns: (1) overexpression in the endogenous expression domain, (2) expression instead of Mesp2 (Ripply2-knockin), and (3) ectopic expression in the entire PSM. We found accelerated Tbx6 degradation in the embryos showing Ripply2 overexpression. In the Ripply2-knockin embryos, the anterior limit of Tbx6 domain was generated by Ripply2 even in the absence of Mesp2. Ectopic Ripply2 expression along the entire PSM suppressed Tbx6 and induced Sox2-positive neural tube formation at the bilateral domain, resembling the Tbx6-null phenotype. This phenotype resulted from Tbx6 protein and not mRNA elimination, suggesting the post-translational down-regulation of Tbx6 by Ripply2. Taken together, our results demonstrate that Ripply2 represses Tbx6 in a Mesp2-independent manner, which contributes to the accurate segmental border formation.
authors: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Wei
authors: W
authors: Zhao
authors: Department of Genetics, SOKENDAI, Japan; National Institute of Genetics, Research Organization of Information and Systems, Yata 1111, Mishima, Shizuoka 411-8540, Japan.
authors: Rieko
authors: R
authors: Ajima
authors: National Institute of Genetics, Research Organization of Information and Systems, Yata 1111, Mishima, Shizuoka 411-8540, Japan.
authors: Youichirou
authors: Y
authors: Ninomiya
authors: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan; Department of Genetics, SOKENDAI, Japan; National Institute of Genetics, Research Organization of Information and Systems, Yata 1111, Mishima, Shizuoka 411-8540, Japan. Electronic address: ysaga@nig.ac.jp.
authors: Yumiko
authors: Y
authors: Saga
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D015153:Blotting, Western; D019521:Body Patterning / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D055879:Gene Knock-In Techniques; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D051379:Mice; D008822:Mice, Transgenic; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D019170:Somites / Q000196:embryology* / Q000378:metabolism; D020825:T-Box Domain Proteins; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D017931:DNA Primers; D012097:Repressor Proteins; D020825:T-Box Domain Proteins; D014157:Transcription Factors; C107407:Mesp2 protein, mouse; C520509:Ripply2 protein, mouse; C102932:Tbx6 protein, mouse
keywords: Presomitic mesoderm; Ripply2; Segmentation; Somitogenesis; Tbx6