Show simple item record

dc.contributor.authorZielinska, Agata Pamela
dc.date.accessioned2018-11-13T10:46:20Z
dc.date.available2018-11-13T10:46:20Z
dc.date.issued2020-06-14
dc.date.submitted2018-07-02
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/285004
dc.description.abstractPoor egg quality is the leading cause of pregnancy loss and Down’s syndrome. While even eggs in young women frequently contain an incorrect number of chromosomes and are therefore unlikely to give rise to a viable pregnancy, the incidence of chromosomally abnormal eggs increases strikingly with advancing maternal age. Why egg quality declines dramatically as women approach their forties remains one of the outstanding questions in developmental biology. This PhD thesis demonstrates how unforeseen features of kinetochore organization that are unique to meiosis render this cell division process in mammals particularly prone to errors. Firstly, my results uncovered an unexpected multi-subunit organization of the meiotic kinetochore, which is widely conserved across mammals and biases eggs towards errors. Secondly, I identified two independent mechanisms that predispose eggs from older women to aneuploidy. The first mechanism affects the fidelity of meiosis I. My analysis revealed that human oocytes challenge the paradigm that sister kinetochores are fully fused. Instead, I demonstrated that sister kinetochores disjoin as women get older, which promoted erroneous kinetochore-microtubule attachments. This in turn allowed chromosomes to rotate on the spindle and provided a mechanistic explanation for reverse segregation - a recently discovered meiotic error that is unique to humans. Secondly, I pioneered the use of super-resolution microscopy to study chromosome architecture in human eggs and discovered that individual kinetochores during meiosis II in mammals are composed of previously unidentified subdomains. In young females, these subdomains are joined together by cohesin complexes. With age, kinetochores fragment into two pieces. Fragmented kinetochores frequently attach merotelically to spindle microtubules, which predisposes aged eggs to errors. What severely hinders our progress in identifying causes of human infertility is that numerous features of human meiosis are not represented in mice. To overcome this challenge, I developed an experimental platform to mimic the age-related changes that occur in humans in oocytes from young mice. I achieved this by extending the applications of Trim-Away, a novel method to degrade endogenous proteins even in primary cells, to partially deplete proteins. Furthermore, I established a new experimental model system to study human-like aspects of meiosis in live non-rodent cells in real time: pig oocytes. Together, these results set foundations for new therapeutic approaches to extend reproductive lifespan by counteracting the age-related loss in kinetochore integrity that this study identified. Furthermore, partial Trim-Away and studying meiosis in pigs opens new directions for meiotic research.
dc.description.sponsorshipRosetrees Trust School of Clinical Medicine, University of Cambridge
dc.language.isoen
dc.rightsAll rights reserved
dc.rightsAll Rights Reserveden
dc.rights.urihttps://www.rioxx.net/licenses/all-rights-reserved/en
dc.subjectoocyte
dc.subjectmeiosis
dc.subjecthuman
dc.subjectmouse
dc.subjectpig
dc.subjectmaternal age-effect
dc.subjectageing
dc.subjectkinetochore
dc.subjectmicrotubule
dc.subjectcohesin
dc.titleSTUDIES IN OOCYTES FROM THREE MAMMALIAN SPECIES DEMONSTRATE THAT MEIOTIC KINETOCHORES ARE COMPOSED OF PREVIOUSLY UNIDENTIFIED SUBDOMAINS AND REVEAL TWO NOVEL MECHANISMS BEHIND THE MATERNAL-AGE EFFECT IN HUMANS
dc.typeThesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnameDoctor of Philosophy (PhD)
dc.publisher.institutionUniversity of Cambridge
dc.publisher.departmentMRC Laboratory of Molecular Biology
dc.date.updated2018-11-01T00:17:53Z
dc.identifier.doi10.17863/CAM.32375
dc.publisher.collegeTrinity
dc.type.qualificationtitlePhD in Natural Sciences
cam.supervisorSchuh, Melina
cam.supervisorBullock, Simon
cam.thesis.fundingfalse
rioxxterms.freetoread.startdate2400-01-01


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record