Takeuchi Masaki    Department   Kawasaki University of Medical Welfare  ,    Position   Associate Professor
Language	English
Title	The early embryogenesis of Polypterus (bichirs): Insights into the origin and evolution of vertebrate body plans
Conference	20th CDB Meeting: Molecular Bases for Evolution of Complex Traits
Conference Type	International society and overseas society
Presentation Type	Poster notice
Lecture Type	General
Publisher and common publisher	◎Masaki Takeuchi, Maiko Takahashi, Shinichi Aizawa
Date	2011/02/23
Venue (city and name of the country)	Kobe, Japan
Summary	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. Here I would like to discuss about insights from bichir (most basal ray-finned fish) embryogenesis into these evolution in vertebrates. Importantly, bichir embryogenesis is similar to amphibian rather than teleost, in many aspects such as holoblastic cleavage. All blastomeres in amphibian develop into the primary germ layers. However, not only in bichir but also in agnathan lamprey, meso-endoderm develop in the marginal zone, and vegetal cell mass is extraembryonic yolk cells. This suggests that the lamprey/bichir holoblastic development is ancestral to extant vertebrates, that their pattern was responsible for the frequent transitions from holoblastic to meroblastic cleavage as a pre-pattern in the vertebrate lineage, and that amphibian holoblastic development was acquired secondarily accompanied by the exploitation of lineage-specific molecular machineries such as maternal VegT. An additional topic is about the existence and significance of a bichir homolog of Xsiamois, which is the head inducible gene previously found only in amphibian. It is suggested that siamois-related protogene was required for the axis formation in the common ancestor of Osteichthyes.