RNA EDITOME ANALYSIS OF HEMATOPOIETIC CELLS REVEALS ANTIZYME INHIBITOR 1 AS A FUNCTIONAL REGULATOR IN HEMATOPOIETIC STEM AND PROGENITOR CELLS

RNA editing, adenosine (A)-to-inosine (I), plays a vital role in many biological processes. Our previous study has demonstrated that the hematopoietic stem and progenitor cells (HSPCs) deficient in adenosine deaminase acting on RNA 1 (Adar1), an RNA-editing enzyme, cannot reconstitute the irradiated recipients in vivo and form colonies in vitro (Xufeng R et al, PNAS 2009). However, the overall profile of RNA editome in hematopoiesis has not been established and the underlying mechanism how RNA editing governs the function of HSPCs is poorly defined. In this study, we sorted 12 murine adult hematopoietic cell populations and performed RNA sequencing. We depicted the landscape of RNA editome in hematopoietic cells and identified 30,796 editing sites in total. By charactering specific editing sites in different hematopoietic cell subsets at different stages, we found that the antizyme inhibitor 1 (Azin1) was highly edited in coding region in HSPCs as opposed to other cell types. To understand whether edited Azin1 was required for functioning of HSPCs, we transduced c-Kit+ HSPCs with the lentivirus carrying Azin1 cDNAs with distinct editing frequencies. c-Kit+ cells transduced with fully edited Azin1 showed enhanced reconstitution, compared to that transduced with partially edited or non-edited Azin1. Specifically, inability of RNA editing in Azin1 blocked the differentiation of hematopoietic stem cells (HSCs) in vivo. Moreover, a similar finding was obtained when Azin1 was knocked down. In summary, for the first time, this study provides a landscape of specific editing sites in hematopoietic cascade and demonstrates a pivotal role of the RNA-editable gene, Azin1, in hematopoietic stem and progenitor cells.