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dc.contributor.advisorMonty Krieger.en_US
dc.contributor.authorWang, Li,Ph.D.Massachusetts Institute of Technology.en_US
dc.contributor.otherMassachusetts Institute of Technology. Department of Biology.en_US
dc.date.accessioned2019-11-04T20:20:28Z
dc.date.available2019-11-04T20:20:28Z
dc.date.copyright2019en_US
dc.date.issued2019en_US
dc.identifier.urihttps://hdl.handle.net/1721.1/122709
dc.descriptionThesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2019en_US
dc.descriptionCataloged from PDF version of thesis. Page 236 blank.en_US
dc.descriptionIncludes bibliographical references.en_US
dc.description.abstractThe high-density lipoprotein (HDL) receptor SR-BI controls the structure and fate of plasma HDL. The SR-BI knockout (KO) females are infertile, apparently due to their abnormal, cholesterol-enriched HDL particles. In this thesis, my colleagues and I examined the growth and meiotic progression of SR-BI KO oocytes and found that they underwent normal germinal vesicle breakdown; however, SR-BI KO eggs, which had accumulated excess cholesterol in vivo, spontaneously activated; they escaped metaphase II (MII) arrest and progressed to pronuclear, metaphase III and anaphase/telophase III stages. Eggs from fertile, wild-type mice were activated when loaded in vitro with excess cholesterol using a cholesterol/methyl-[beta]-cyclodextrin complex, phenocopying SR-BI KO oocytes.en_US
dc.description.abstractIn vitro cholesterol loading of eggs induced elevation of intracellular calcium (the [Ca²⁺]i spike), reduction in MPF and MAPK activities, extrusion of a second polar body and progression to meiotic stages beyond MI. These results suggest the infertility of SR-BI KO females is due, at least in part, to excess cholesterol in eggs inducing premature activation, and that cholesterol can activate wild-type mouse eggs to escape from MII arrest. In the Chapter 3, I studied the detailed mechanism of egg activation induced by excess cholesterol. I showed that the [Ca²⁺]i spike induced by excess cholesterol was necessary for egg activation and also sufficient for further development of the egg to the blastocysts stage. Excess cholesterol, in calcium free medium, did not induce changes in [Ca²⁺]i, indicating that extracellular calcium was required for the [Ca²⁺]i spike and also suggesting the entry of extracellular calcium via plasma membrane channel(s).en_US
dc.description.abstractAfter screening of calcium channel inhibitors, single cell mRNA-sequencing and activation experiments using eggs from mutant females, I was able to show that co-inhibition of both the L-type calcium channel Ca[subscript v]1.3 and the transient receptor potential channel TRPC5, but not inhibition of either one alone, blocked the excess-cholesterol induced [Ca²⁺]i spike and egg activation. This result suggests that excess cholesterol activates the MII eggs by opening of Ca[subscript v]1.3 or TPRC5. Our results raise the possibility that excess cholesterol might also activate the same channels in other systems, and thus contribute to pathophysiology.en_US
dc.description.statementofresponsibilityby Li Wang.en_US
dc.format.extent236 pagesen_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsMIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582en_US
dc.subjectBiology.en_US
dc.titleCholesterol and egg activationen_US
dc.typeThesisen_US
dc.description.degreePh. D.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Biologyen_US
dc.identifier.oclc1123217440en_US
dc.description.collectionPh.D. Massachusetts Institute of Technology, Department of Biologyen_US
dspace.imported2019-11-04T20:20:27Zen_US
mit.thesis.degreeDoctoralen_US
mit.thesis.departmentBioen_US


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