Grundy Martin, Lucken Kellie, Xing Xiaomeng, Simpson Eva L, Worker Alice, Bayyoomi Ahmed, Beckett Alison J, Prior Ian A, Booth Daniel G, Seedhouse Claire H
Translational Medical Sciences, Biodiscovery Institute, University of Nottingham, Nottingham NG7 2RD, United Kingdom.
Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7BE, UK.
J Cell Sci. 2025 May 15;138(10). doi: 10.1242/jcs.263553. Epub 2025 May 21.
Mutations in the nucleophosmin (NPM1) gene represent the most common genetic alteration in acute myeloid leukaemia (AML) and result in mis-localisation of the mutated protein from a predominantly nucleolar localisation to a predominantly cytoplasmic distribution. Here, we use high resolution imaging to demonstrate that NPM1 is crucial for maintaining normal nucleoli architecture and specifically the integrity of the enigmatic nucleoli rim, the least understood nucleolar compartment. We demonstrate that cell lines and primary cells with NPM1 mutations from individuals with AML have aberrant nucleoli architecture; intriguingly this abnormal nucleolar phenotype is reversible. Using a surrogate for rRNA synthesis, we show that the aberrant phenotype is associated with differences in nucleolar function; specifically, activity of RNA polymerase I is increased in NPM1 mutated cells. Perinucleolar chromatin organisation is also markedly different in NPM1 mutant cells. Finally, we report the novel finding that NPM1 mutated protein forms distinct aggregates and characterise these for the first time. This work reveals how nucleolar organisation contributes to the molecular mechanisms underpinning NPM1-driven AML, revealing novel therapeutic vulnerabilities.
核磷蛋白（NPM1）基因的突变是急性髓系白血病（AML）中最常见的基因改变，会导致突变蛋白的定位从主要在核仁转变为主要在细胞质分布。在此，我们利用高分辨率成像证明，NPM1对于维持正常的核仁结构至关重要，特别是对于神秘的核仁边缘（了解最少的核仁区室）的完整性。我们证明，来自AML患者的携带NPM1突变的细胞系和原代细胞具有异常的核仁结构；有趣的是，这种异常的核仁表型是可逆的。通过使用rRNA合成的替代指标，我们表明异常表型与核仁功能差异有关；具体而言，RNA聚合酶I的活性在NPM1突变细胞中增加。核仁周围染色质组织在NPM1突变细胞中也明显不同。最后，我们报告了一个新发现，即NPM1突变蛋白形成不同的聚集体，并首次对其进行了表征。这项工作揭示了核仁组织如何促成NPM1驱动的AML的分子机制，揭示了新的治疗靶点。
