Tuesday, April 23, 2024
4/23/2024
Project Summary The development of complex organisms requires diversification of cell types and tissues. Cells such as stem cells and embryos must polarize in order to segregate cell fate determinants, and then divide asymmetrically to generate functionally distinct cells. Failure to establish cell polarity is a hallmark of many cancers and developmental defects. Therefore, it is of great importance to understand how cell polarity network is coupled with the cell cycle, to get insights into how specific cell types are formed during development. PAR proteins are specialized proteins that govern proper establishment of cell polarity in many organisms. For example, mouse embryonic stem cells establish apical-basal polarity by localizing PAR proteins to the apical or basal domains to allow the segregation of cell fate determinants. Another example is the Caenorhabditis elegans zygote, which establishes antero-posterior polarity by forming mutually exclusive PAR cortical domains. However how PAR proteins are regulated is not fully understood. Recent studies have revealed that a cell cycle kinase, Aurora A, is required to initiate polarization in a C. elegans zygote. These studies showed evidence that Aurora A exhibits dynamic localization and acts at different stages of the cell cycle to control cortical recruitment of PAR proteins in a timely and precise manner. However, the exact mechanisms by which Aurora A modulates PAR protein asymmetries remain obscure. The overreaching objectives of this proposal are to dissect how different pools of Aurora A transmit signals that promote timely and precise cell polarization, and to determine if the role of Aurora A during polarization is conserved in other polarizing cells. The central hypothesis is that Aurora A works at different times and places to modulate polarity proteins organizations, thereby coordinating polarity with the cell cycle. This hypothesis will be tested using a unique biochemical approach for quantifying protein-protein interactions at a single cell, single molecule level, in combination with high-resolution microscopy and targeted genome editing. Experiments in Aim 1 will identify Aurora A substrates in C. elegans and test how loss of Aurora A activity impacts PAR proteins localization and complex assembly. Aim 2 will determine where and when Aurora A activity is required to coordinate PAR proteins, using optogenetics to manipulate Aurora A spatial regulation and commercially available Aurora A inhibitors to control the Aurora A activity. Aim 3 will assess whether Aurora A activity is required during apical-basal polarity establishment of mouse embryonic stem cells. Collectively, these data will reveal how Aurora A is positioned to orchestrate polarity proteins dynamics and complex assembly and provide fundamental knowledge of how polarity is established and synchronized with the cell cycle.
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