beta-Catenin in early development of the lancelet embryo indicates specific determination of embryonic polarity.
The lancelet (amphioxus) embryo develops from a miolecithal egg and starts gastrulation when it is approximately 400 cells in size, in a fashion similar to that of some non-chordate deuterostomes. Throughout this type of gastrulation, the embryo develops characteristics such as the notochord and hollow nerve cord that commonly appear in chordates. beta-Catenin is an important factor in initiating body patterning. The behavior and developmental pattern of this protein in early lancelet development was examined in this study. Cytoplasmic beta-catenin was localized to the animal pole after fertilization and then was incorporated asymmetrically into the blastomeres during the first cleavage. Asymmetric distribution was observed at least until the 32-cell stage. The first nuclear localization was at the 64-cell stage, and involved all of the cells. At the initial gastrula stage, however, concentrated beta-catenin was found on the dorsal side. LiCl treatment affected the asymmetric pattern of beta-catenin during the first cleavage. LiCl also changed distribution of nuclear beta-catenin at the initial gastrula stage: distribution extended to cells on the animal side. Apparently associated with this change, expression domains of goosecoid, lhx3 and otx also changed to a radially symmetric pattern centered at the animal pole. However, LiCl-treated embryos were able to establish embryonic polarity. The present study suggests that in the lancelet embryo, polarity determination is independent of dorsal morphogenesis.
Yasui
Kinya
K
Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, China. furaha@gpo.kumamoto-u.ac.jp
Li
Guorong
G
Wang
Yong
Y
Saiga
Hidetoshi
H
Zhang
Peijun
P
Aizawa
Shinichi
S
D000818:Animals; D036703:Blastula / Q000378:metabolism; D019521:Body Patterning / Q000502:physiology*; D002816:Chordata, Nonvertebrate / Q000196:embryology*; D002970:Cleavage Stage, Ovum / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D051176:beta Catenin
D003598:Cytoskeletal Proteins; D015534:Trans-Activators; D051176:beta Catenin