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 (bichir) ~Insights into the Origin and Evolution of Developmental Mechanisms in Vertebrates~
会議名	CDB Symposium
学会区分	国際学会及び海外の学会
発表形式	ポスター掲示
講演区分	一般
発表者・共同発表者	◎Takeuchi Masaki, Aizawa Shinichi
発表年月日	2013/03/04
開催地 （都市, 国名）	Kobe, Japan
学会抄録	CDB Symposium 2013. The Making of a Vertebrate 268-269
概要	Germ layer patterning and body axis formation are central issues in vertebrate embryology. An intriguing question is how the mechanisms that existed in an ancestral vertebrate have been modified during vertebrate evolution. A major stream of vertebrates (Osteichthyes) evolved into two monophyletic lineages: Sarcopterygii, including amphibians and amniotes, and Actinopterygii (ray-finned fishes), including teleosts as the crown group. Bichir diverged from all other actinopterygians soon after this divarication. Therefore, bichir is uniquely well suited for studies assessing the ancestral state of Osteichthyes/Actinopterygii as well as understanding the divergence of embryogenesis in teleosts and amphibians. Importantly, bichir embryogenesis is quite similar to that of amphibian rather than teleost, not only in its holoblastic cleavage but also in many aspects. Amphibian holoblastic cleavage in which all blastomeres contribute to any one of the three primary germ layers has been widely thought to be a developmental pattern in the stem lineage of vertebrates. However, in holoblastic development of not only bichir but also agnathan lamprey, meso-endoderm develop in the marginal zone, and vegetal cell mass is extraembryonic yolk cells. In order to explain these results, we present the viewpoint that the lamprey/bichir holoblastic development would have been ancestral to extant vertebrates and retained in their stem lineage. Their pattern might have been responsible for the frequent transitions from holoblastic to meroblastic cleavage as a pre-pattern in the vertebrate lineage. Amphibian holoblastic development would have been acquired secondarily, accompanied by the exploitation of lineage-specific molecular machineries such as maternal VegT.