Growth Factor Independence 1 (GFI1) is a transcriptional repressor that plays a critical role during both myeloid and lymphoid haematopoietic lineage commitment. Several studies have demonstrated the involvement of GFI1 in haematological malignancies and have suggested that low expression of GFI1 is a negative indicator of disease progression for both myelodysplastic syndromes (MDS) and acute myeloid leukaemia (AML). In this study, we have stratified AML patients into those defined as having a normal karyotype (CN-AML). Unlike the overall pattern in AML, those patients with CN-AML have a poorer survival rate when GFI1 expression is high. In this group, high GFI1 expression is paralleled by higher FLT3 expression, and, even when the FLT3 gene is not mutated, exhibit a FLT3-ITD signature of gene expression. Knock-down of GFI1 expression in the human AML Fujioka cell line led to a decrease in the level of FLT3 RNA and protein and to the down regulation of FLT3-ITD signature genes, thus linking two major prognostic indicators for AML.

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SummaryAdipose tissues (ATs) are innervated by sympathetic nerves, which drive reduction of fat mass via lipolysis and thermogenesis. Here, we report a population of immunomodulatory leptin receptor (LepR)-expressing barrier cells which ensheath sympathetic axon bundles in adipose tissues. These LepR-expressing Sympathetic Perineurial Cells (SPCs) produce IL33, a factor for maintenance and recruitment of regulatory T cell (Treg) and eosinophils in AT. Brown adipose tissues (BAT) of mice lacking IL33 in SPCs (SPCIL33cKO) have fewer Treg and eosinophils, resulting in increased BAT inflammation. SPCIL33cKOmice are more susceptible to diet-induced obesity, independently of food intake. Furthermore, SPCIL33cKOmice have impaired adaptive thermogenesis, and are unresponsive to leptin-induced rescue of metabolic adaptation. We, therefore, identify LepR-expressing SPCs as a source of IL33 which orchestrate an anti-inflammatory environment in BAT, preserving sympathetic-mediated thermogenesis and body weight homeostasis. LepR+IL33+SPCs provide a cellular link between leptin and immune regulation of body weight, unifying neuroendocrinology and immunometabolism as previously disconnected fields of obesity research.Graphical AbstractHighlights-Sympathetic Perineurial Cells (SPCs) co-express LepR+and IL33-SPC-derived IL33 prevents BAT inflammation via Treg and eosinophil recruitment-Obesity is worsened in high fat diet-fed SPCIL33cKOmice, despite normal food intake-Adaptive thermogenesis is impaired in SPCIL33cKOmice-Rescue of metabolic adaptation to fasting by leptin is impaired in SPCIL33cKOmice-SPCs link leptin to immunometabolic regulation of body weight homeostasis

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