Loss of Tifab, a del(5q) MDS gene, alters hematopoiesis through derepression of Toll-like receptor-TRAF6 signaling.

The Journal of experimental medicine 2015 Oct 19

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TRAF-interacting protein with forkhead-associated domain B (TIFAB) is a haploinsufficient gene in del(5q) myelodysplastic syndrome (MDS). Deletion of Tifab results in progressive bone marrow (BM) and blood defects, including skewed hematopoietic stem/progenitor cell (HSPC) proportions and altered myeloid differentiation. A subset of mice transplanted with Tifab knockout (KO) HSPCs develop a BM failure with neutrophil dysplasia and cytopenia. In competitive transplants, Tifab KO HSPCs are out-competed by wild-type (WT) cells, suggesting a cell-intrinsic defect. Gene expression analysis of Tifab KO HSPCs identified dysregulation of immune-related signatures, and hypersensitivity to TLR4 stimulation. TIFAB forms a complex with TRAF6, a mediator of immune signaling, and reduces TRAF6 protein stability by a lysosome-dependent mechanism. In contrast, TIFAB loss increases TRAF6 protein and the dynamic range of TLR4 signaling, contributing to ineffective hematopoiesis. Moreover, combined deletion of TIFAB and miR-146a, two genes associated with del(5q) MDS/AML, results in a cooperative increase in TRAF6 expression and hematopoietic dysfunction. Re-expression of TIFAB in del(5q) MDS/AML cells results in attenuated TLR4 signaling and reduced viability. These findings underscore the importance of efficient regulation of innate immune/TRAF6 signaling within HSPCs by TIFAB, and its cooperation with miR-146a as it relates to the pathogenesis of hematopoietic malignancies, such as del(5q) MDS/AML. © 2015 Varney et al.

Citation

Melinda E Varney, Madeline Niederkorn, Hiroyasu Konno, Takayuki Matsumura, Jin Gohda, Nobuaki Yoshida, Taishin Akiyama, Susanne Christie, Jing Fang, David Miller, Andres Jerez, Aly Karsan, Jaroslaw P Maciejewski, Ruhikanta A Meetei, Jun-ichiro Inoue, Daniel T Starczynowski. Loss of Tifab, a del(5q) MDS gene, alters hematopoiesis through derepression of Toll-like receptor-TRAF6 signaling. The Journal of experimental medicine. 2015 Oct 19;212(11):1967-85