タケウチ　マサキ   Takeuchi Masaki   竹内　雅貴    所属   川崎医療福祉大学  医療技術学部 臨床検査学科    職種   准教授
言語種別	英語
発表タイトル	The early embryogenesis of Polypterus (bichirs): Insights into the origin and evolution of vertebrate body plans
会議名	International Workshop [Evolving shapes and development - viewed from changes in gene regulations]
学会区分	全国規模の学会
招聘	招聘
発表形式	口頭
講演区分	シンポジウム・ワークショップ パネル（その他）
発表者・共同発表者	◎Masaki Takeuchi
発表年月日	2010/08/04
開催地 （都市, 国名）	Tokyo, Japan
概要	Germ layer patterning and body axis formation are central issues in vertebrate embryology. Our intriguing question is how the mechanisms of embryogenesis that existed in ancestors have been modified during vertebrate evolution. Vertebrate ancestors would have increased their egg size to store yolk, and the increase is considered to account for change of cleavage pattern and germ layer formation. Because the holoblastic cleavage in which all blastomeres contribute to a part of the primary germ layers is conserved in amphibian and protochordates, it has been widely thought to be a developmental pattern in the stem lineage of vertebrates. Embryogenesis of bichir, the most basal ray-finned fish, is quite similar to that of amphibian rather than teleost, not only in its holoblastic cleavage but also in many aspects. However, in holoblastic development of not only bichir but also agnathan lamprey, meso-endoderm develop only in the equatorial marginal zone, and the vegetal cell mass consists of extraembryonic yolk cells. The study raises the viewpoint that the lamprey/bichir holoblastic development would have been ancestral to extant vertebrates and retained in their stem lineage; amphibian holoblastic development would have been acquired secondarily, accompanied by the exploitation of new molecular machinery such as maternal VegT.