Lnk/Sh2b3 deficiency restores hematopoietic stem cell function and genome integrity in Fancd2 deficient Fanconi anemia

Joanna Balcerek,Jian-Gang Ren,Yang Li,Jing Jiang,Weihua Li,Brijendra Singh,Krasimira Rozenova,Kaosheng Lv,Wei Tong,Vemika Chandra,Qinqin Jiang,Nicholas Holdreith,Roger A Greenberg

doi:10.1038/s41467-018-06380-1

Abstract

Fanconi anemia (FA) is a bone marrow failure (BMF) syndrome that arises from mutations in a network of FA genes essential for DNA interstrand crosslink (ICL) repair and replication stress tolerance. While allogeneic stem cell transplantation can replace defective HSCs, interventions to mitigate HSC defects in FA do not exist. Remarkably, we reveal here that Lnk (Sh2b3) deficiency restores HSC function in Fancd2−/− mice. Lnk deficiency does not impact ICL repair, but instead stabilizes stalled replication forks in a manner, in part, dependent upon alleviating blocks to cytokine−mediated JAK2 signaling. Lnk deficiency restores proliferation and survival of Fancd2−/− HSCs, while reducing replication stress and genomic instability. Furthermore, deletion of LNK in human FA-like HSCs promotes clonogenic growth. These findings highlight a new role for cytokine/JAK signaling in promoting replication fork stability, illuminate replication stress as a major underlying origin of BMF in FA, and have strong therapeutic implications.

Highlights

Fanconi anemia (FA) is a bone marrow failure (BMF) syndrome that arises from mutations in a network of FA genes essential for DNA interstrand crosslink (ICL) repair and replication stress tolerance
We previously reported that Lnk deficiency potentiates JAK2 activation in hematopoietic stem and progenitor cell (HSPC), which in part accounts for its role in Hematopoietic stem cells (HSCs) self-renewal[25,26,27,31]
We found that wild type (WT), Lnk−/−, and Fancd2−/−Lnk−/− HSPCs were all sensitive to JAK inhibitor ruxolitinib (JAKi) in stabilizing stalled replication fork (Fig. 6f)

Summary

Introduction

Fanconi anemia (FA) is a bone marrow failure (BMF) syndrome that arises from mutations in a network of FA genes essential for DNA interstrand crosslink (ICL) repair and replication stress tolerance. These additional functions of the FA/BRCA proteins play a critical role in preventing genomic instability and suppressing tumorigenesis[18,19,20] It remains to be determined how they are regulated by extracellular signals during physiologic hematopoiesis and whether stalled replication fork stability contributes to HSC attrition and BMF in vivo. LNK did not overtly affect ICL repair in Fancd2−/− cells but reduced spontaneous DNA damage and genome instability This correlated with Lnk deficiency alleviating replication stress by stabilizing stalled replication forks in a manner dependent upon cytokine-mediated JAK2 signaling. These findings shed light on the underlying origin of BMF in FA patients and have implications for new therapeutic strategies

Methods

Results

Conclusion