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	The 34th Annual Meeting of the Molecular Biology Society of Japan
学会区分	全国規模の学会
発表形式	ポスター掲示
講演区分	一般
発表者・共同発表者	◎Masaki Takeuchi, Maiko Takahashi, Shinichi Aizawa
発表年月日	2011/12/14
開催地 （都市, 国名）	Yokohama, Japan
概要	Germ layer patterning and body axis formation are central issues in vertebra te embryology. Our intriguing question is how the mechanisms that existed in an ancestral vertebrate have been modified during vertebrate evolution. Polypterus (bichirs, a basalmost ray-finned fishes) is a suitable model representing the nonteleost ray-finned fishes because of its phylogenic posi tion and morphological features. Importantly, bichir embryogenesis is quite similar to that of amphibians rather than teleosts. However, the yolky veget al cell mass generated by the holoblastic cleavage in bichir and agnathan la mprey embryos, differently from Xenopus embryos, is not endodermal bu t extraembryonic. Therefore, we propose the idea that bichir/lamprey-type ho loblastic development is ancestral to that of the extant vertebrates and tha t their pattern has been responsible for the frequent transitions from holob lastic to meroblastic cleavage as a pre-pattern in the vertebrate lineage. M eanwhile, germ layer patterning in the extant amphibian lineage might have b een acquired secondarily by the exploitation of lineage-specific molecular m achinery, such as the maternal VegT.<BR>As an additional topic, we re port about the existence and significance of a siamois-related gene i n bichir. Xenopus siamois is a homeobox gene coding for a transcripti onal mediator of the dorsal Wnt signaling pathway and is necessary for forma tion of the Spemann's organizer. However, its homologous genes had been neve r found in other taxa. This bichir gene and Xenopus siamois have iden tical protein activity, but each gene plays different roles for bichir or <I Xenopus embryogenesis.