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dc.contributor.advisorKim, Seonhee
dc.creatorSimmons, Ambrosia
dc.date.accessioned2020-11-05T15:01:58Z
dc.date.available2020-11-05T15:01:58Z
dc.date.issued2019
dc.identifier.urihttp://hdl.handle.net/20.500.12613/3573
dc.description.abstractCortical malformations arise from defects in any stage of brain development and often result in life-long disability ranging from epilepsy to developmental delay and even perinatal lethality. The neuroepithelium of the emergent cortex lays the foundation on which the future cortex will develop, and as such, neuroepithelial tissue and the neural progenitor cells (NPCs) which comprise it are critical to the proper growth and development of the cortex. Here I demonstrate the significance of neuroepithelial cell polarity determinants in cortical development and how they affect both junctional integrity and the regulation of NPC proliferation leading to a variety of cortical malformations. Until now, the role of basal polarity complex protein Lgl1 in cortical development remained elusive due to perinatal lethality in animal models. To bypass this, we developed a novel conditional knockout mouse model of Lgl1 in the neuroepithelium and show that Lgl1 is essential to the maintenance of neuroepithelial integrity and regulation of NPC proliferation. Loss of Lgl1 results in a displaced ventricular zone with widespread ectopic proliferation resulting in severe periventricular nodular heterotopia (PNH). Furthermore, Lgl1 loss reduces the cell cycle length resulting in hyperproliferation leading to neuronal overproduction. Together, this work identifies a novel genetic cause of PNH. Next, I aimed to characterize the interaction of Lgl1 with other polarity proteins and downstream signaling pathways in cortical development. Apical and basal polarity proteins have demonstrated mutual antagonism in the establishment/maintenance of epithelial polarity; however, little is known about the role of this antagonism on cortical size and structure or the signaling pathways through which it acts. To address these questions we generated multiple genetic mouse models to investigate the opposing roles of basal protein, Lgl1, and either apical proteins Pals1 or Crb2. Concurrent loss of Pals1 and Lgl1 was able to prevent heterotopic nodules and increase proliferation compared to loss of Pals1 alone. However, cortical size was severely diminished due to overriding effects of Pals1 on cell survival that was unmitigated by Lgl1 loss. Remarkably, loss of both Crb2 and Lgl1 restored the cortex and hippocampus to near normal morphology with a profound rescue of cortical size, suggesting their essential antagonism in both cortical and hippocampal development. Importantly, genetic manipulation through reduction of YAP/TAZ expression in the Lgl1 CKO eliminates periventricular nodules and restores cortical thickness to that of WT cortices. This important finding implicates Lgl1 in the regulation of YAP/TAZ in cortical development. Finally, we investigated a possible downstream target of Pals1 in cell survival, BubR1. My work demonstrates that loss of Pals1 reduces BubR1 expression, which is an essential regulator of the mitotic checkpoint and causative gene of the human disorder Mosaic Variegated Aneuploidy. I show that loss of BubR1 results in significant apoptosis across all cell types in the cortex leading to microcephaly. These data provide the first link between cell polarity determinants and mitotic regulation in the cortex and suggests that BubR1 reduction likely contributes to the decreased cell survival following Pals1 loss. Overall these findings implicate impaired polarity complex function in a wide variety of NPC defects resulting in multiple cortical malformations. My work shows that polarity proteins regulate every stage of the NPCs life cycle from cell division and proliferation to cell survival through regulation of mitosis and YAP/TAZ signaling.
dc.format.extent164 pages
dc.language.isoeng
dc.publisherTemple University. Libraries
dc.relation.ispartofTheses and Dissertations
dc.rightsIN COPYRIGHT- This Rights Statement can be used for an Item that is in copyright. Using this statement implies that the organization making this Item available has determined that the Item is in copyright and either is the rights-holder, has obtained permission from the rights-holder(s) to make their Work(s) available, or makes the Item available under an exception or limitation to copyright (including Fair Use) that entitles it to make the Item available.
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectNeurosciences
dc.subjectCellular Biology
dc.titleThe Role of Polarity Complex Proteins in Neural Progenitor Proliferation
dc.typeText
dc.type.genreThesis/Dissertation
dc.contributor.committeememberCrino, Peter
dc.contributor.committeememberCho, Seo-Hee
dc.contributor.committeememberGoetzl, Laura
dc.contributor.committeememberPopoff, Steven N.
dc.description.departmentBiomedical Sciences
dc.relation.doihttp://dx.doi.org/10.34944/dspace/3555
dc.ada.noteFor Americans with Disabilities Act (ADA) accommodation, including help with reading this content, please contact scholarshare@temple.edu
dc.description.degreePh.D.
refterms.dateFOA2020-11-05T15:01:58Z


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