Trebonia kvetii gen. nov., sp. nov., an acidophilic actinobacterium, and proposal of the new actinobacterial family Treboniaceae fam. nov.

A novel actinobacterial strain, designated 15TR583T, was isolated from a waterlogged acidic soil collected near the town of Trebon, Czech Republic, and was subjected to a polyphasic taxonomic characterization. Phylogenetic analysis based on 16S rRNA gene and whole-genome sequences revealed that the organism forms an individual line of descent related to the order Streptosporangiales, class Actinomycetia. The strain shared highest 16S rRNA gene sequence similarity, yet of only 92.8%, with Actinocorallia aurea IFO 14752T. The strain grew in white colonies of aerobic, Gram-stain-positive, unbranching substrate mycelium bearing single spores at hyphae tips. The major fatty acids (>10%) were iso-C16 : 0, C16 : 0, iso-C17 : 1ω9 and 10-methyl-C17 : 0. The fatty acid pattern differed from all patterns currently described for actinobacterial genera. The organism contained as major menaquinones MK9(H6) and MK9(H8), which differentiated it from other actinobacterial families. Polar lipids were composed of six unidentified glycolipids, an unidentified phosphoglycolipid, two unidentified phospholipids and two unidentified aminolipids. Whole-cell sugars contained galactose, xylose and arabinose as major components. The peptidoglycan type was A1γ meso-diaminopimelic acid. The genomic DNA G+C content was 69.7 mol%. The distinct phylogenetic position and unusual combination of chemotaxonomic characteristics justify the proposal of Trebonia gen. nov., with the type species Trebonia kvetii sp. nov. (type strain 15TR583T=CCM 8942T=DSM 109105T), within Treboniaceae fam. nov.

Nuclear factor of activated T-cells, NFATC1, governs FLT3ITD-driven hematopoietic stem cell transformation and a poor prognosis in AML.

BACKGROUND: Acute myeloid leukemia (AML) patients with a high allelic burden of an internal tandem duplication (ITD)-mutated FMS-like Tyrosine Kinase-3 (FLT3) have a dismal outcome. FLT3ITD triggers the proliferation of the quiescent hematopoietic stem cell (HSC) pool but fails to directly transform HSCs. While the inflammatory transcription factor nuclear factor of activated T-cells 2 (NFAT2, NFATC1) is overexpressed in AML, it is unknown whether it plays a role in FLT3ITD-induced HSC transformation. METHODS: We generated a triple transgenic mouse model, in which tamoxifen-inducible Cre-recombinase targets expression of a constitutively nuclear transcription factor NFATC1 to FLT3ITD positive HSC. Emerging genotypes were phenotypically, biochemically, and also transcriptionally characterized using RNA sequencing. We also retrospectively analyzed the overall survival of AML patients with different NFATC1 expression status. RESULTS: We find that NFATC1 governs FLT3ITD-driven precursor cell expansion and transformation, causing a fully penetrant lethal AML. FLT3ITD/NFATC1-AML is re-transplantable in secondary recipients and shows primary resistance to the FLT3ITD-kinase inhibitor quizartinib. Mechanistically, NFATC1 rewires FLT3ITD-dependent signaling output in HSC, involving augmented K-RAS signaling and a selective de novo recruitment of key HSC-transforming signaling pathways such as the Hedgehog- and WNT/B-Catenin signaling pathways. In human AML, NFATC1 overexpression is associated with poor overall survival. CONCLUSIONS: NFATC1 expression causes FLT3ITD-induced transcriptome changes, which are associated with HSC transformation, quizartinib resistance, and a poor prognosis in AML.

Development, Function, and Clinical Significance of Plasmacytoid Dendritic Cells in Chronic Myeloid Leukemia.

Plasmacytoid dendritic cells (pDC) are the main producers of a key T-cell-stimulatory cytokine, IFNα, and critical regulators of antiviral immunity. Chronic myeloid leukemia (CML) is caused by BCR-ABL, which is an oncogenic tyrosine kinase that can be effectively inhibited with ABL-selective tyrosine kinase inhibitors (TKI). BCR-ABL-induced suppression of the transcription factor interferon regulatory factor 8 was previously proposed to block pDC development and compromise immune surveillance in CML. Here, we demonstrate that pDCs in newly diagnosed CML (CML-pDC) develop quantitatively normal and are frequently positive for the costimulatory antigen CD86. They originate from low-level BCR-ABL-expressing precursors. CML-pDCs also retain their competence to maturate and to secrete IFN. RNA sequencing reveals a strong inflammatory gene expression signature in CML-pDCs. Patients with high CML-pDC counts at diagnosis achieve inferior rates of deep molecular remission (MR) under nilotinib, unless nilotinib therapy is combined with IFN, which strongly suppresses circulating pDC counts. Although most pDCs are BCR-ABL-negative in MR, a substantial proportion of BCR-ABL + CML-pDCs persists under TKI treatment. This could be of relevance, because CML-pDCs elicit CD8+ T cells, which protect wild-type mice from CML. Together, pDCs are identified as novel functional DC population in CML, regulating antileukemic immunity and treatment outcome in CML.Significance: CML-pDC originates from low-level BCR-ABL expressing stem cells into a functional immunogenic DC-population regulating antileukemic immunity and treatment outcome in CML. Cancer Res; 78(21); 6223-34. ©2018 AACR.

Vitamin A-Retinoic Acid Signaling Regulates Hematopoietic Stem Cell Dormancy.

Dormant hematopoietic stem cells (dHSCs) are atop the hematopoietic hierarchy. The molecular identity of dHSCs and the mechanisms regulating their maintenance or exit from dormancy remain uncertain. Here, we use single-cell RNA sequencing (RNA-seq) analysis to show that the transition from dormancy toward cell-cycle entry is a continuous developmental path associated with upregulation of biosynthetic processes rather than a stepwise progression. In addition, low Myc levels and high expression of a retinoic acid program are characteristic for dHSCs. To follow the behavior of dHSCs in situ, a Gprc5c-controlled reporter mouse was established. Treatment with all-trans retinoic acid antagonizes stress-induced activation of dHSCs by restricting protein translation and levels of reactive oxygen species (ROS) and Myc. Mice maintained on a vitamin A-free diet lose HSCs and show a disrupted re-entry into dormancy after exposure to inflammatory stress stimuli. Our results highlight the impact of dietary vitamin A on the regulation of cell-cycle-mediated stem cell plasticity. VIDEO ABSTRACT.