Elucidating how epithelial cell polarity maintenance safeguards genome stability during cell division.

极化的上皮细胞分裂是在组织动态平衡和形态发生过程中将命运决定因素和基因组物质正确分配到子细胞中的关键机制，它们的破坏可能导致严重的发育障碍和疾病，如过早衰老和癌症。然而，协调细胞极性、正确的有丝分裂纺锤体动力学和染色体分离保真度以确保适当的上皮完整性和分化的确切机制仍不清楚。在最近的一次筛查中，我们发现了一个新的蛋白质复合体，包括膜相关Annexin A1(ANXA1)蛋白及其伴侣S100A11，它与乳腺上皮细胞中进化保守的LGN有丝分裂复合体相互作用。初步观察表明，ANXA1-S100A11复合体的破坏会导致纺锤体动力学缺陷和染色体异常分离，导致胞质分裂缺陷和细胞-细胞黏附功能受损。这个合作项目将为博士生提供细胞生物学和生物技术方面的尖端多学科培训，结合3D和超分辨率成像来测试ANXA1-S100A11协调细胞极性、纺锤体动态和忠实的染色体对齐和分离以确保上皮完整性的假设。为了具体研究ANXA1-S100A11复合体在有丝分裂中的作用，博士生将使用CRISPR/Cas9基因组编辑来产生表达内源性退化标记的ANXA1和S100A11的乳腺上皮细胞，以诱导细胞分裂过程中的急性蛋白质耗竭。通过结合先进的超分辨率显微镜技术，这位博士生将在纳米级剖析ANXA1-S100A11复合体在协调细胞与细胞黏附分子、LGN纺锤体定向机制和染色体稳定性调节(也在我们的屏幕中发现)动态中的作用(S)。这位博士生将进一步扩展干细胞来源的乳腺3D有机体结合3D共聚焦成像的研究，以评估ANXA1-S100A11缺失介导的缺陷在形态发生过程中对上皮完整性和分化的影响。该项目将提供一个重要的机制洞察ANXA1-S100A11(可能是第一个特征蛋白复合体)如何连接细胞极性控制和染色体稳定，以确保适当的上皮结构和防止恶性转化。我们的发现将被用于BBSRC或MRC项目赠款的更雄心勃勃的建议，使用鼠标和数学模型来研究体内这些机制的破坏如何导致过早衰老和癌症。

Polarised epithelial cell divisions represent a critical mechanism for correct partitioning of fate determinants and genomic material into the daughter cells during tissue homeostasis and morphogenesis, and their disruption can lead to severe developmental disorders and diseases such as premature aging and cancer. Yet, the precise mechanisms coordinating cell polarity and correct mitotic spindle dynamics and chromosome segregation fidelity, to ensure proper epithelial integrity and differentiation remain ill defined. In a recent screen, we identified a novel protein complex including the membrane-associated Annexin A1 (ANXA1) protein and its partner S100A11 that interacts with the evolutionarily conserved LGN mitotic complex in mammary epithelial cells. Preliminary observations, show that disruption of ANXA1-S100A11 complex results in defective spindle dynamics and abnormal chromosome segregation, leading to cytokinesis defects and impaired cell-cell adhesion. This collaborative project will provide the PhD student with a cutting-edge multidisciplinary training in cell biology and biotechnology combined with 3D and super-resolution imaging to test the hypothesis that ANXA1-S100A11 coordinates cell polarity, spindle dynamic and faithful chromosome alignment and segregation to ensure epithelial integrity. To specifically study the role of ANXA1-S100A11 complex during mitosis, the PhD candidate will employ CRISPR/Cas9 genome editing to generate mammary epithelial cells expressing endogenously degron-tagged ANXA1 and S100A11 to induce acute protein depletion during cell division. By combining advanced and super-resolution microscopy technology, the PhD student will dissect the role(s) of ANXA1-S100A11 complex in the coordination of the dynamics of cell-cell adhesion molecules, LGN spindle orientation machinery and chromosome stability regulators (also identified in our screen) in a nanoscale. The PhD student will further extend the study in stem cell-derived mammary 3D organoids combined with 3D confocal imaging to assess the impact of ANXA1-S100A11-loss-mediated defects on epithelial integrity and differentiation during morphogenesis. This project will provide a significant mechanistic insight on how ANXA1-S100A11 (probably the first characterised protein complex) bridges cell polarity control and chromosome stability maintenance to ensure proper epithelial architecture and prevent malignant transformation. Our findings will be used for more ambitious proposals for BBSRC or MRC project grants, using mouse and mathematical models to investigate how disruption of these mechanisms in vivo can contribute to premature aging and cancer.