[Recent contributions to the establishment of the axes of the mammalian embryo].
The study of the establishment of embryonic axes during early development has shown that this process is a very early event (occurRing either during ovogenesis or during fertilization) for invertebrates and for lower vertebrates. In mammals, it was considered that this establishment appears late during development because of the great plasticity of blastomeres. Recent data in the mouse embryon show that the mammalian ovocyte is a polarized cell, the polar body corresponding to the animal pole of this cell. The blastomeres that are generated by the zygote divide asynchronously. The first that divides is the one which inherits the plasma cell membrane where fertilization takes place. This blastomere will preferentially give rise to the cells of the embryonic pole of the blastocyst whereas the other yields the cells of the abembryonic pole. The mammalian ovocyte is thus a polarized cell with an already established animal-vegetal axis. The point of sperm entry will determine the embryonic-abembryonic axis.
Catala
M
M
Laboratoire d'Histologie et Embryologie et UMR CNRS 7000, Faculté de Médecine Pitié-Salpétrière, Université Paris 6, 105, boulevard de l'Hôpital, 75634 Paris, France. catala@ext.jussieu.fr
D000818:Animals; D001757:Blastomeres / Q000648:ultrastructure; D016764:Cell Polarity; D005314:Embryonic and Fetal Development; D005260:Female; D005306:Fertilization; D008297:Male; D008322:Mammals / Q000196:embryology*; D051379:Mice; D009024:Morphogenesis; D009865:Oocytes / Q000648:ultrastructure; D009866:Oogenesis; D013084:Sperm-Ovum Interactions; D015053:Zygote / Q000648:ultrastructure