Ripply2 recruits proteasome complex for Tbx6 degradation to define segment border during murine somitogenesis

• DOI: 10.7554/elife.33068
• Publication Date: 2018-05-15T09:00:09Z
• Authors: Wei Zhao; Masayuki Oginuma; Rieko Ajima; Makoto Kiso; Akemi Okubo; Yumiko Saga
• Keywords: Proteasome Endopeptidase Complex; QH301-705.5; Science; Mass Spectrometry; presomitic mesoderm; Mice; 03 medical and health sciences; somitogenesis; Animals; Biology (General); Cells, Cultured; 0303 health sciences; segmentation; Q; R; Mouse Embryonic Stem Cells; Repressor Proteins; proteasome; Somites; Proteolysis; Medicine; T-Box Domain Proteins; Developmental Biology; Protein Binding; Transcription Factors

The metameric structure in vertebrates is based on the periodic formation of somites from the anterior end of the presomitic mesoderm (PSM). The segmentation boundary is defined by the Tbx6 expression domain, whose anterior limit is determined by Tbx6 protein destabilization via Ripply2. However, the molecular mechanism of this process is poorly understood. Here, we show that Ripply2 directly binds to Tbx6 in cultured cells without changing the stability of Tbx6, indicating an unknown mechanism for Tbx6 degradation in vivo. We succeeded in reproducing in vivo events using a mouse ES induction system, in which Tbx6 degradation occurred via Ripply2. Mass spectrometry analysis of the PSM-fated ES cells revealed that proteasomes are major components of the Ripply2-binding complex, suggesting that recruitment of a protein-degradation-complex is a pivotal function of Ripply2. Finally, we identified a motif in the T-box, which is required for Tbx6 degradation independent of binding with Ripply2 in vivo.