The Role of CUX1 in Erythropoiesis

Anemia is a significant cause of morbidity and mortality in myeloid malignances. Cytogenetic changes are recurrent within malignant hematopoietic stem and progenitor cells, yet their role in anemia pathogenesis remains unknown. One recurrent karyotypic abnormality in myeloid neoplasms is the deletion of part or all of chromosome 7 [-7/del(7q)], which harbors the transcription factor and tumor suppressor gene, CUX1. CUX1 knockdown mouse models develop myeloid disease similar to that seen in humans, including a spontaneous, cell intrinsic, and lethal anemia that develops with age. Here, we elucidate the cellular and molecular mechanisms by which CUX1 regulates erythropoiesis. We demonstrate CUX1 knockdown mice have an aberrant stress erythropoiesis response and decreased survival after acute anemia induction. CUX1 insufficient erythroblasts undergo accelerated cell cycling and increased apoptosis. In line with these phenotypes, transcriptome profiling indicates that CUX1-knockdown elicits increased proliferation and decreased erythroid differentiation gene signatures. ATAC-sequencing demonstrated dramatic, global chromatin opening in CUX1-knockdown erythroblasts. As measured by fluorescence lifetime imaging microscopy, this increased chromatin accessibility is concomitant with a disruption in nuclear condensation, which is normally requisite in mammalian erythroblasts for nuclear eviction and terminal differentiation. Finally, we show that CUX1 mediates chromatin compaction by promoting histone deacetylation. Thus, our data implicate in an epigenetic regulatory role for CUX1 in erythropoiesis. Furthermore, these results suggest therapeutic targeting of epigenetic regulators, such as histone acetyl transferases, may have clinical benefit for the anemias associated with loss of CUX1.