BioProject

Blockades in hematopoiesis deprive the host of vital blood cells and frequently cause leukemia. More...

Blockades in hematopoiesis deprive the host of vital blood cells and frequently cause leukemia. Here we show that inactivation of mTORC1 in hematopoietic stem cells by deletion of Raptor unmasked a cell type, hereby called myelolymphoblastic innate cell (MLIC) based on unique gene expression signature, cell surface markers, morphology and functions. The MLICs are CD11b(+)Gr-1(-)B7-H1(high)F4/80(low) and have morphology of lymphoblasts with active Ig loci but no gene rearrangement. Within weeks of Raptor deletion, the MLICs account for nearly 50% of bone marrow cells and are found throughout both the lymphoid and non-lymphoid organs. Nevertheless, the MLICs are not malignant as they undergo very limited proliferation in vivo. Importantly, the MLICs broadly express pattern-recognition receptors and produce large amounts of inflammatory cytokines in response to all TLR ligands tested, rendering the host highly susceptible to pathogen-associated molecular patterns. Our data suggest that hematopoietic cell-intrinsic mTORC1 prevents development of self-destructive innate immune attack by suppressing generation of MLICs. Overall design: Raptor F/F mice were crossed with Mx1-Cre mice for more than 2 generations to get Raptor F/F (Ctrl) and Raptor F/F, Mx1-Cre (cKO) mice. Sex-matched 6-8 weeks old Ctrl mice and cKO mice were treated with polyinosinic: polycytidylic acid (pIpC) every other day for consecutive 7 times by intra-peritoneal (i.p.) injection to induce Cre expression and Raptor deletion in mouse hematopoietic system. Raptor mice were sacrificed 2-3 weeks after the last injection of pIpC. Whole BM cells from Raptor Ctrl mice (n=3) and FACS-sorted CD11b(+)Gr-1(-) BM MLICs from Raptor cKO mice (n=3) were used for RNA isolation and subsequent cDNA libraries construction. mRNA profiles of Ctrl-WBM and cKO-MLIC were examined by RNA-sequencing, in triplicate, using Illumina HiSeq 2000. Less...