ABIN1 (Q478) is Required to Prevent Hematopoietic Deficiencies through Regulating Type I IFNs Expression

Abstract A20‐binding inhibitor of NF‐κB activation (ABIN1) is a polyubiquitin‐binding protein that regulates cell death and immune responses. Although Abin1 is located on chromosome 5q in the region commonly deleted in patients with 5q minus syndrome, the most distinct of the myelodysplastic syndromes (MDSs), the precise role of ABIN1 in MDSs remains unknown. In this study, mice with a mutation disrupting the polyubiquitin‐binding site (Abin1^Q478H/Q478H) is generated. These mice develop MDS‐like diseases characterized by anemia, thrombocytopenia, and megakaryocyte dysplasia. Extramedullary hematopoiesis and bone marrow failure are also observed in Abin1^Q478H/Q478H mice. Although Abin1^Q478H/Q478H cells are sensitive to RIPK1 kinase–RIPK3–MLKL‐dependent necroptosis, only anemia and splenomegaly are alleviated by RIPK3 deficiency but not by MLKL deficiency or the RIPK1 kinase‐dead mutation. This indicates that the necroptosis‐independent function of RIPK3 is critical for anemia development in Abin1^Q478H/Q478H mice. Notably, Abin1^Q478H/Q478H mice exhibit higher levels of type I interferon (IFN‐I) expression in bone marrow cells compared towild‐type mice. Consistently, blocking type I IFN signaling through the co‐deletion of Ifnar1 greatly ameliorated anemia, thrombocytopenia, and splenomegaly in Abin1^Q478H/Q478H mice. Together, these results demonstrates that ABIN1(Q478) prevents the development of hematopoietic deficiencies by regulating type I IFN expression.