ATAC-Seq of sorted murine LT-HSCs segemented on intial CUX1 levels with and without CUX1 knockdown.

Hematopoietic stem cells (HSCs) possess properties of both self-renewal and multipotent differentiation; however, the regulation of these opposing properties remains elusive. Using a novel reporter mouse, we demonstrate the dose-dependent role of the transcription factor, CUX1, in HSC fate. As CUX1 levels naturally rise, HSCs gradually lose repopulating capacity. CUX1 knockdown reverses this process and reverts HSCs to an earlier cell state—restoring the transcriptome, chromatin accessibility, repopulating capacity, and self-renewal ability of HSCs with normally low CUX1 levels. In the absence of CUX1, endogenous retroelements (EREs) are aberrantly expressed, leading to a cell-intrinsic inflammatory response, which contributes to CUX1-dependent HSC activity. Likewise, loss of the transcription factor IRF1 attenuates CUX1-mediated HSC reprogramming. This mechanism could be relevant to leukemogenesis as acute myeloid leukemias with CUX1 deletions upregulate EREs and the interferon response. Our findings attribute CUX1 and innate immune activation to the complex molecular underpinnings of HSC fate decisions.