FBXW11 VARIANTS DECREASED HSCS QUIESCENCE AND MYELOID-BIASED DIFFERENTIATION IN VIVO

Abstract

Hematopoietic stem cells (HSCs) maintain their balance of self-renewal and differentiation under the regulation of sophisticated signal transduction networks. However, the intrinsic molecular mechanism that regulates this transformative property remains elusive. Fbxw11, as a constituent of the SCF (Skp1-Cul1-F box) ubiquitin ligase complex, can target for degradation several important transcription factors. So, Fbxw11 may play a pivotal role in many aspects of hematopoiesis through regulating various signal transduction pathways. In this study, we found that the expression of Fbxw11were lower in long term hematopoietic stem cell (LT‐HSCs), and higher in hematopoietic stem and progenitor cells (LSK) and various hematopoietic progenitor cells compared with BM cells. Competitive repopulation assays were performed and we observed that Fbxw11-overexpressed HSCs impaired their ability to repopulation. Colony-forming cell assay (CFC) showed that the number of CFU-GEMM, CFU-GM, CFU-G and the total number of CFU were lower in LSK with overexpression of Fbxw11 variants when compared with LSK control. Hoechst 33342 and Ki67 staining assay showed that the percentage of LSK cells in G0 phase was decreased when Fbxw11 overexpression. Fbxw11-overexpressed HSCs expressed lower level of self-renewal associated transcription factors, such as HoxA5, Hoxbl3, Myc, Sox2 and Tim1, suggesting that Fbxw11 decreased the self-renewal ability of HSCs. Fbxw11 also led to a progressive enlargement of myeloid population and reduce of lymphocyte population. Fbxw11-overexpressed HSCs expressed higher level of myeloid differentiation associated Csf1r, CSF2r and Runx1. Our results, therefore, demonstrate a critical and unique role for Fbxw11 in regulating self-renewal of HSCs and myeloid differentiation.