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研究発表を行った学会；
・第４５回日本発生生物学会
　２０１２年　５月２８日〜３１日（神戸）

タイトル；Swelling force of the amniotic cavity supports notochordal extension by controlling cell orientation in mouse embryos.

発表者；藺牟田　雄　氏
　　　（熊本大学　発生医学研究所　分化制御分野）
Abstract；
Vertebrate body is formed from anterior to posterior direction, and this axis extension process is controlled by multiple mechanisms including proliferation of axial progenitor cells, gastrulation, planar cell polarity (PCP) signaling etc. In this study, we focused on extension of the midline tissue, notochord, in E7.5 to E8.25 mouse embryos, and found that expansion of the amniotic cavity is an important factor controlling this process. To study cell behaviors in the node and the notochord, we generated　 Foxa2:H2B-EGFP knock-in mice, which express nuclear-localized fluorescent protein in the node, the notochord and the endoderm. In vitro time-lapse imaging of E7.5 Foxa2: H2B-EGFP embryos revealed that the notochord cells divide along　 antero-posterior axis, which is distinct from the surrounding endoderm cells dividing along left-right axis. Notochordal cells were initially oriented along left-right axis, but re-oriented along antero-posterior axis during in vitro culture. Similar re-orientation of notochordal cells was also observed with freshly dissected embryos between E7.5 to E8.25. Amniotic cavity swells as development proceeds during in vitro culture, and piercing the amnion and yolk sac with a glass capillary, thereby reducing the inner pressure of the amniotic cavity, suppressed its swelling. Such capillary inserted embryos developed with reduced swelling of amniotic cavity, and these embryos failed to undergo re-orientation of the notochordal cells. Re-orientation initiates prior to activation of PCP signaling detected by membrane localization of Dvl2-EGFP proteins. Taken together, we propose a model by which the mechanical force that drives swelling of the amniotic cavity supports antero-posterior extension of the notochord by promoting re-orientation of the notochordal cells, and this mechanism operates upstream or parallel to the PCP signaling.