Research is proposed to test the hypothesis that sperm chromatin dispersion is coordinate with the activity of the maternal chromatin, i.e. changes in nucleocytoplasmic interactions effecting the status/function of the maternal genome also influence the pattern of sperm chromatin dispersion at fertilization. Recent investigations demonstrate that sperm nuclear dispersion does not proceed at a uniform rate but consists of four phases coordinate with major changes in the activity of the maternal chromosones. The presence of distinct phases in the rate of dispersion indicates the existence of major differences in the regulation of chromatin dispersion. What mechanisms comprise each of these phases and how they are related to one another and conditions regulating the status/function of the maternal chromatin are aspects to be explored during the course of this study. Experiments will (1) determine and compare the rate of sperm nuclear dispersion in ova fertilized at different stages of meiotic maturation and (2) determine the kinetics of chromatin dispersion in eggs that, normally fertilized at one stage of meiotic maturation, are inseminated at a different period. If the kinetics of sperm chromatin dispersion is related to the activity of the maternal chromatin, disruption of the normal functioning of the maternal chromatin or factors regulating the status of the maternally derived genome may be reflected in alterations of sperm nuclear transformation. Stages of meiotic maturation of the maternal chromatin will be perturbed and possible effects on the rate of sperm chromatin dispersion will be analyzed. Experiments will be carried out in which the rate of sperm chromatin dispersion will be compared in fertilized nucleate and enucleate eggs and in specimens treated with agents to disrupt the meiotic apparatus. If the kinetics of sperm chromatin dispersion is related to factors regulating the activity of the maternal chromatin, this may be demonstrated by experiments, where extracts from eggs at one stage of fertilization are microinjected into zygotes at a different stage. Correlation of alterations in sperm chromatin dispersion with stages of fertilization from which microinjected extracts were obtained would support the proposed hypothesis. It is anticipated that results of these experiments will lead to further studies, injecting specific components into zygotes, and eventually characterizing regulators of sperm nuclear transformations at fertilization.
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