MYC Promotes Bone Marrow Stem Cell Dysfunction in Fanconi Anemia

We profiled primary HSPCs from Fanconi anemia (FA) patients for single cell transcriptome (scRNA-seq) to identify additional determinants of HSPC impairment leading to the bone marrow failure,. Trajectory analysis revealed that early hematopoietic differentiation potential is preserved in FA HSPCs. As expected, p53 and TGFβ pathway genes were overexpressed in HSPCs from FA patients. The oncogene MYC was also identified as one of the top over-expressed genes in FA HSPCs. Interestingly, we observed co-existence of “High-TP53” expressing HSPCs and HighMYC expressing HSPCs in FA bone marrow. Inhibition of MYC expression by the BET bromodomain inhibitor (+)-JQ1 reduced the clonogenic potential of primary HSPCs from FA patients but rescued the physiological/genotoxic stress in HSPCs from FA mice. The “High-MYC” expressing HSPCs exhibited a significant downregulation of cell adhesion genes, such as CXCR4. Consistently, HSPCs in FA patients showed a defect in adhesion to their bone marrow niche resulting in egression from the bone marrow into peripheral blood. We speculate that MYC overexpression impairs HSPC function and contributes to exhaustion of HSPCs in FA bone marrow. Expression profiles of single cells from seven Fanconi Anemia patients and five healthy donors.