The objective of this proposal is to determine whether autophagy, a highly conserved cellular process, plays a role in mammalian preimplantation development and whether metabolism-induced alterations to this event result in abnormal embryo growth and development. Our mouse models of abnormal embryonic glucose transport, both diabetic and genetic, which we established during the last grant cycle, all experience increased blastocyst apoptosis and result in significant growth deficiencies, some accompanied by specific congenital malformations. Similar growth abnormalities are seen in embryos lacking autophagy proteins as well, and other recent studies suggest that basal autophagy during development is critical to balancing proliferation and apoptosis in response to nutrient supply. Our preliminary data suggest that defects in glucose transport, whether gene knockout mice, antisense mice or controls exposed to abnormal conditions during the first 96 hours post fertilization, persist into adulthood, suggesting that growth deficiencies may be """"""""programmed"""""""" in to the embryos from the earliest stages of development. We hypothesize that autophagy may play an important role in this process by regulating the degradation of proteins and also modulating apoptosis. In this case, changes in glucose transport leading to changes in autophagy in the blastocyst stage embryo may program development and pregnancy outcomes. These studies are highly innovative since they are some of the first to examine the role of autophagy in mammalian embryo development and pregnancy outcome. Our rationale is that poor pregnancy outcomes related to fluctuations in glucose availability may be avoidable and/or reversible by changing the pattern of autophagy. These studies aim to test this hypothesis.
Specific Aim 1 examines the baseline amount of autophagy in wildtype preimplantation embryos and determines if in vitro manipulation of this process results in blastocyst abnormalities which change pregnancy outcome.
Specific Aim 2 evaluates the effect of manipulating autophagy in established mouse models of glucose transporter deficiencies and whether these changes affect embryo development and competence.
Specific Aim 3 investigates the possible role GLUT8 may play in autophagy in the mouse blastocyst. The results of this study will establish the role of abnormal protein degradation seen in altered autophagic states during mammalian preimplantation development. Models of excess or deficient autophagy result in embryonic lethality and abnormal neuroepithelium, however, the etiology and timing of this developmental insult are unknown. These proposed experiments will attempt to explore this phenomenon and perhaps provide ideas for therapeutic interventions to improve pregnancy rates in patients with diabetes, recurrent pregnancy loss as well as patients undergoing IVF.
In this proposal, we hypothesize that basal autophagy in the murine blastocyst is regulated by metabolic milieu changes and can alterations in autophagy can result in poor pregnancy outcomes. Blastocysts from diabetic mice exhibit changes in autophagic pathways, as do genetic models of decreased glucose uptake. By modulating the rate of autophagy during the preimplantation period in these models and then transferring these embryos into surrogate mice, the outcomes of these manipulations are determined.
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