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アクティブボード・２００２年１０月
研究発表を行った学会；日本動物学会第７３回大会
２００２年９月２４日～２７日（金沢）
タイトル；ヒガシナメクジウオの癒合双生胚における左右非対称性
発表者；安井 金也 氏
（発生医学研究センター 胚形成部門 系統発生分野）
Abstract；
Molecular models for left-right asymmetric development have been proposed for vertebrates. To examine whether or not the proposed models are applicable to cephalochordates, we have studied left-right asymmetric patterns using conjoined twins. All but an exception were dicephalic conjoined twins regardless of whether they arose spontaneously orwere induced artificially. Three types of left-right asymmetry in the twins were identified according to expression pattern of BbPtx. The first group was twins retaining their own original laterality, being the majority in spontaneous twins. The second group showed a mirror image found in twins induced by an electricpulse, in which the left twin expressed BbPtx on the leftside and the right twin on the right side. The last had two anterior bodies, but a head developed two mouths bilaterally and theother was headless. These patterns are inconsistent with the molecular model for amniotes but favor in part the left-right coordinator model for Xenopus. Embryos with defect in dorsalformation, induced by LiCl, established and retained the normal dorso-ventral and left-right polarities. Unlike vertebrates, left-side expression of nodal appeared later than that of BbPtx. These observations suggest that in the lancelet embryo left-right determinant(s) like Vg1 in Xenopus may directly activate BbPtx in the anterior region, and once sinistral expression is established, it persists without midline barrier.
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