TIRAP Drives Marrow Failure through an Ifn-Hmgb1 Axis That Disrupts the Endothelial Niche

The myelodysplastic syndrome (MDS) are a group of hematological malignancies with the propensity to develop into either acute myeloid leukemia (AML) or bone marrow failure (BMF). Dysregulation of immune and inflammatory responses has been implicated in MDS and other BMF disorders. There is significant evidence for IFNγ playing a key role in MDS and BMF syndromes. However, there are conflicting theories regarding the mechanism by which IFNγ promotes BMF. There is also very little information on the triggers that underlie upregulation of IFNγ in these BMF syndromes. Interstitial deletion of chromosome 5q is the most common cytogenetic abnormality observed in MDS, accounting for approximately 10% of all cases. Our lab has previously shown that miR-145, which is located on the minimally deleted region of chromosome 5q, targets Toll/Interleukin-1 receptor domain containing adaptor protein (TIRAP) - an innate immune adaptor protein. However, the role of TIRAP in marrow failure has not been well elucidated. In this study, we identify a novel role for TIRAP in dysregulating normal hematopoiesis through activation of Ifnγ.