Many common birth defects result from defective morphogenesis. Our primary working hypothesis is that morphogenesis depends on cell polarity, which is established and maintained by cell surface-cytoskeletal interactions that are sensitive to asymmetric cell-cell contacts. Our objective is to investigate this hypothesis using mouse blastocyst formation as an experimental model of mammalian morphogenesis. Blastocyst formation entails two interrelated events, 1) cavitation and 2) differentiation of trophectoderm and inner cell mass (ICM). This project focuses on the morphogenetic details of cavitation, which is critical to trophectoderm/ICM differentiation. I have proposed the Metabolic Cavitation Model to explain cavitation and production of nascent blastocoele fluid. The unique features of this model are: 1) Production of nascent blastocoele fluid depends on cytoplasmic polarity consisting of the asymmetric distribution of organelles (mitochondria and lipid droplets) that accumulate along apposed cell surfaces. 2) Maintenance of cytoplasmic polarity depends on: a. properties of the plasma membrane that distinguish free- from apposed cell surfaces; b. cell surface-cytoskeletal interactions that are sensitive to asymmetric cell-cell contacts; c. transcellular ion currents that enter free (apical) surfaces and leave apposed (basolateral) surfaces of blastomeres having asymmetric cell-cell contacts (the outer blastomeres of the morula). 3) Water in nascent blastocoele fluid results from beta-oxidation of lipid droplets.
The Specific Aims will test these features of the Metabolic Cavitation Model. Plant lectins will be used (immunofluorescence/immunoperoxidase techniques) to selectively label specific plasma membrane domains together with treatments to disrupt cytoskeletal elements and cell surface-cytoskeletal associations. Effects on organelle distribution will be quantitated by morphometric analyses at the electron microscopic (EM) level. Isolated blastomeres will be subjected to electric fields to obtain information on how molecules are segregated to specific plasma membrane domains. Lipid catabolism during cavitation will be quantitated by morphometric analyses at the EM level.
|Peters, J M; Wiley, L M; Zidenberg-Cherr, S et al. (1993) Influence of periconceptional zinc deficiency on embryonic plasma membrane function in mice. Teratog Carcinog Mutagen 13:15-21|
|Wiley, L M; Lever, J E; Pape, C et al. (1991) Antibodies to a renal Na+/glucose cotransport system localize to the apical plasma membrane domain of polar mouse embryo blastomeres. Dev Biol 143:149-61|
|Peters, J M; Wiley, L M; Zidenberg-Cherr, S et al. (1991) Influence of short-term maternal zinc deficiency on the in vitro development of preimplantation mouse embryos. Proc Soc Exp Biol Med 198:561-8|
|Wiley, L M; Obasaju, M F (1989) Effects of phlorizin and ouabain on the polarity of mouse 4-cell/16-cell stage blastomere heterokaryons. Dev Biol 133:375-84|
|Obasaju, M F; Wiley, L M; Oudiz, D J et al. (1989) A chimera embryo assay reveals a decrease in embryonic cellular proliferation induced by sperm from X-irradiated male mice. Radiat Res 118:246-56|
|Obasaju, M F; Wiley, L M; Oudiz, D J et al. (1988) An assay using embryo aggregation chimeras for the detection of nonlethal changes in X-irradiated mouse preimplantation embryos. Radiat Res 113:289-99|
|Wiley, L M; Obasaju, M F (1988) Induction of cytoplasmic polarity in heterokaryons of mouse 4-cell-stage blastomeres fused with 8-cell- and 16-cell-stage blastomeres. Dev Biol 130:276-84|
|Obasaju, M F; Wiley, L M; Miller, L et al. (1987) Reproductive effects of chlorpromazine exposure to female mice: cell proliferation disadvantage revealed by the Chimera Embryo Assay. Reprod Toxicol 1:17-23|
|Wiley, L M; Yamami, S; Van Muyden, D (1986) Effect of potassium concentration, type of protein supplement, and embryo density on mouse preimplantation development in vitro. Fertil Steril 45:111-9|
|Wiley, L M; Obasaju, M F (1986) Immunofluorescent localization of immunoglobulins on the cell surface of mouse oocytes and preimplantation embryos. J In Vitro Fert Embryo Transf 3:319-25|
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