Although culture systems exist that support mouse oocyte maturation, fertilization, and preimplantation in vitro, there is still a large gap in our knowledge regarding the molecular bases of these processes. Moreover, such well defined In vitro culture systems are still lacking for other mammalian species. Four unresolved areas exist that relate directly to the ability of in vitro culture systems to support the processes of oocyte maturation, fertilization, and preimplantation development. First, the molecular basis for 'hardening' of the zona pellucida, which occurs during oocyte maturation in vitro and is correlated with the development of a metaphase II-arrested egg of reduced fertilizabilty, is still poorly understood.
The first aim of this grant is to purify from serum/follicular fluid the component(s) that inhibits modification of the zona pellucida during mouse oocyte maturation, to ascertain if the zona pellucida modification occurs during oocyte maturation in other species, and to determine if this serum/follicular fluid component(s) inhibits the modification of the zona pellucida in other species. Second, the regulation of the onset of embryonic gene transcription is poorly understood in any mammalian species.
The second aim of this grant is to identify proteins whose synthesis is a marker for transcriptional activation, and to define the role of protein phosphorylation in this process in other mammalian species, as well as to determine the effect of different culture media on embryonic gene transcription. Third, the function of endogenously produced growth factors by preimplantation embryos in development is not well-defined.
The third aim of this grant is to analyze the effect of different culture media on the expression of different growth factors and their receptors during preimplantation development of several mammalian species, and to determine biochemical and physiological responses of blastocysts to these growth factors. Last, the role of apical, trophectoderm protein secretion in implantation is poorly understood, and there is a paucity of information concerning any potential function of proteins that are secreted into the blastocoel in the regulation of Inner cell mass proliferation and differentiation.
The fourth aim of this grant is to analyze the effect of different culture media on the types of proteins secreted by blastocysts into the medium (apical) and into the blastocoel in several mammalian species. The comparative approach proposed in this grant will afford insights into common underlying biochemical and molecular mechanisms that regulate early development.
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