Asymetric segregation of cell determinants in embryos with regulatory development

Asymmetric segregation of cell determinants specific the cell fates in early embryonic development. In C. Elegans somatic and germ cells are separeted in early development. On the basis of the first five asymmetric divisions AB, MS, C, E, D, P4 are found. In this specifications, par genes and genes responsible for the specification of blastomers are involved. P granules are segragated to P4 cells. Xenopus as a representative of amphibians, belonging to a group with regulative embryogenesis , exhibit features of mosaic development like C. Elegans. Maternal RNAs in germ plasm determine germ cells already in oocyte. These RNAs are transported through two distinct pathways. METRO pathways is used for a transportation of mitochondrial cloud RNA. It is specific for Xcat-2, Xpat, XIsirt, Xdazl. Vg1 and VegT RNAs are involved in the second pathway called Vg1 . This RNA contribute to the specification of mesoderm and endoderm. Although mammals reveal regulative development they also exhibit some features of the mosaic embryos. As an example, in the mouse embryo, overexpressing cadherin leads to compaction at the 8 -cell stage. Then the cells of embryo are polarized. Polarized internal cells give rise to ICM. Conversely, the outer nonpolarized cells give rise to TE. Specific factor for TE is Cdx2, for ICM is..