Ovarian differentiation and human embryo quality. 1. Molecular and morphogenetic homologies between oocytes and embryos in Drosophila, C. elegans, Xenopus and mammals.
Knowledge on the formation of oocytes and follicles in Drosophila, C. elegans and Xenopus, and the genetic regulation of polarities and embryo growth, has been related to comparable data in mammalian oocytes and embryos. Initially, details of the nature of the regulatory processes in the non-mammals are described, with considerable attention being paid to the role of individual genes and their specific functions. The molecular genetic aspects of these developmental processes are discussed in detail. Attention then turns to mammals, to identify, describe and evaluate their homologies with the lower animals and flies. Several of these homologies are described, including genes regulating primary ovarian failure and various aspects of early embryonic growth. The polarized distribution of genes in mammalian oocytes and embyros is discussed, together with the implications in the form of differentiation in the early embryo. Morphogenetic systems operative during follicle maturation, fertilization and cleavage are described and related to similar processes in lower forms. These events include ooplasmic and pronuclear rotations, the form of ooplasmic inheritance in early blastomeres and the establishment of embryonic axes. Models of early mammalian development are considered.
Edwards
R. G.
RG
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