Project No. 2418
Dr Salah Elias- University of Southampton
Dr Ruth Murrell-Lagnado – University of Sussex
Polarised epithelial cell divisions represent a fundamental mechanism for tissue maintenance and morphogenesis, their dysregulation often leads to developmental disorders and cancer (1).
A dividing cell must overcome many challenges to produce two daughter cells that have a correct shape and position and that inherit equal amounts of the genetic material. Mitotic progression and outcome are defined by spectacular changes in cell morphology and mechanics, and rearrangements in the microtubule (MT) and actin cytoskeleton. Recent evidence has suggested that ion and water fluxes across the plasma membrane (PM) play a key role in the regulation of the mechanics of mitosis (2). Yet the mechanisms linking the PM to cell shape and size and the mitotic machinery in mammalian epithelial cells remain poorly understood. It remains urgently needed to elucidate these mechanisms, given that maintenance of correct shape and mechanics of mitotic cells throughout mitosis safeguards epithelial function and integrity. We recently identified the PM-associated protein S100A11A (S100 Ca2+-binding protein A11), as being involved in the control of PM dynamics during mitosis in breast epithelial cells. Our preliminary observations show that S100A11 knockdown results in spindle mis-assembly, chromosome mis-segregation, cytokinesis defects and asymmetric partitioning of PM resulting in two daughter cells that differ in size and shape. S100A11A is a regulator of intracellular Ca2+ concentration and cytoskeleton dynamics (3) and is known to interact with TRPM7 (transient receptor potential melastatin 7), a calcium permeable ion channel that also possesses a kinase domain (4). Our hypothesis is that regulation of TRPM7 by S100A11 is critical for its role in mitosis. The aim of this project is to 1) understand how S100A11A regulates the function and PM localization of TRPM7; 2) assess the impact of S100A11 on Ca2+ signalling and how this links to cell size and shape during mitosis; and 3) determine how this influences mitosis outcome and epithelial morphogenesis.
This collaborative project will provide the PhD student with a cutting-edge multidisciplinary training in cell biology and biotechnology combined with advanced immunofluorescence imaging. By combining CRISPR/Cas9-based acute degradation of S100A11 and super-resolution and 3D quantitative live and Ca2+ imaging, the PhD candidate will investigate the impact of S100A11-loss-mediated defects in cell shape and size on the spindle-kinetochore dynamic interaction and determine how this affects chromosome alignment and segregation, mitotic spindle assembly and orientation as well as cytokinesis and the fate and position of the daughter cells. The PhD student will perform the studies in 3D organoid models of normal breast development and tumorigenesis established in Dr Elias lab, combined with 3D live and confocal imaging to assess the impact of S100A11-loss-mediated defects in cell division on epithelial integrity and differentiation during 3D morphogenesis.
This project will provide significant mechanistic insights into the mechanisms bridging PM dynamics, ion transport, cell shape, spindle assembly and chromosome stability maintenance for correct mitotic progression and outcome to ensure proper epithelial architecture and prevent malignant transformation.
1. Santoro, A. et al EMBO Rep (2016) 17, 1700-1720
2. Rizzelli et al. Open Biol (2020) 10(3):190314
3. Zhang et al. Front. Cell Dev. Biol (2021) doi: 10.3389/fcell.2021.693262
4. Cordier et al. (2021) Cancers https://doi.org/10.3390/cancers13246322