Distinct roles of U2AF1 mutations in myelodysplastic syndrome pathogenesis

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PROJECT SUMMARY/ABSTRACT This proposal outlines a 5-year training plan for the transition of the candidate to an independent investigator. The long-term goal of the candidate is to be a physician-scientist at an academic medical center studying the molecular basis of genetic mutations in myelodysplastic syndrome (MDS) pathogenesis, in addition to directing a molecular pathology laboratory. The training plan proposed will expand upon the candidate's clinical and scientific background and provide him access to a supportive environment that will prepare him for a career as an independent investigator. The applicant will be mentored by Dr. Matthew Walter, an expert in MDS genetics and biology and Director of the Edward P. Evans Center for MDS at Washington University (WU). An advisory committee consisting of basic science and clinical/translational MDS experts and pathologists will provide scientific and career advice. The applicant's laboratory is well equipped for these studies, and WU provides a rich environment for training and development as access to core facilities, scientific resources, and clinical samples is exceptional. The experiments outlined in this application aim to clarify the distinct roles of different U2AF1 mutants in MDS pathogenesis, as highly recurrent heterozygous mutations in splicing factor genes (e.g., U2AF1) occur in over half of MDS patients. Hotspot mutations in U2AF1 (encoding U2AF1S34 and U2AF1Q157 mutants) are associated with different clinical features, outcomes, dysregulated RNA splicing, and co-occurring gene mutations in patients with MDS. For example, truncating mutations in ASXL1 cooccur more frequently with U2AF1Q157 than with U2AF1S34 mutations in MDS patients. The candidate has observed U2af1S34F/+ and U2af1Q157R/+ conditional knock-in mice develop different hematopoietic phenotypes, including cytopenias, and have distinct gene expression patterns and aberrant RNA splicing in hematopoietic stem and progenitor cells (HSPC). This proposal aims to understand how the distinct molecular perturbations induced by U2AF1S34F and U2AF1Q157R mutants contribute to the divergent hematopoietic phenotypes observed in MDS patients by determining: (1) how activation of MYC and mTORC1 pathways leads to HSPC dysfunction and multilineage cytopenias in U2af1S34F/+ mice and whether U2AF1S34F-specific splicing alterations result in activation of these pathways, and (2) how mutant ASXL1 and U2AF1Q157 associated histone modification and RNA splicing aberrancies selectively cooperate in MDS pathogenesis. Deciphering the role of MYC and mTORC1 activation will allow these models to be used to test pathway-specific therapeutic strategies to alter cytopenias, and identification of cooperation between ASXL1 and U2AF1 mutations in vivo may reveal novel mechanisms by which RNA splicing and histone modifications synergize in MDS. In sum, the proposed studies and training environment will facilitate the candidate's success in becoming an independent investigator.