Growth hormone controls many facets of a cell's biology through the transcription factors Stat5a and Stat5b (Stat5). However, whole body deletion of these genes from the mouse does not provide portentous information on cell-specific cytokine signaling. To explore liver-specific functions of Stat5, the entire Stat5 locus was deleted in hepatocytes using Cre-mediated recombination. Notably, Stat5-mutant mice developed fatty livers and displayed impaired proliferation of hepatocytes upon partial hepatectomy (PHx). Loss of Stat5 led to molecular consequences beyond the reduced expression of Stat5 target genes, such as those encoding suppressor of cytokine signaling 2 (SOCS2), Cish, and insulin-like growth factor 1 (IGF-1). In particular, circulating growth hormone levels were increased and correlated with insulin resistance and increased insulin levels. Aberrant growth hormone (GH)-induced activation of the transcription factors Stat1 and Stat3 was observed in mutant livers. To test whether some of the defects observed in liver-specific Stat5 deficient mice were due to aberrant Stat1 expression and activation, we generated Stat1 ؊/؊ mice with a hepatocyte-specific deletion of Stat5. Mouse genetics has been employed to dissect the degree to which GH signals through its downstream mediators Stat5 and IGF-1. Inactivation of the GHR gene results in severe postnatal growth retardation, greatly decreased levels of IGF-1, and elevated levels of circulating GH. 1,2 The transcription factors Stat5a and Stat5b are highly conserved and serve overlapping and mostly redundant roles. However, pubertal growth of Stat5b Ϫ/Ϫ males, but not females, is reduced. 3,4 In contrast, normal body growth was observed in both Stat5a Ϫ/Ϫ males and females. 4,5 The complete deletion of the entire Stat5a/b locus resulted in perinatal lethality, 6 suggesting that Stat5 has a more important role than previously considered.It can be hypothesized that the loss of Stat5 will alter the physiology of a cell, because it also controls the transcription of genes encoding suppressor of cytokine signaling 2 (SOCS2) and SOCS3, which are negative regulators of cytokine signaling. Moreover, loss of Stat5 would result in vacant recruitment sites on receptors, which could lead to the activation of other STATs and their downstream targets. To further explore the complexity of the GHStat5 regulatory network in liver, we deleted the Stat5 locus specifically in hepatocytes using Cre-mediated re-

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Aims/hypothesis: The specific contributions made by the various cell types in adipose tissue to obesity, particularly obesity-related inflammation, need to be clarified. The aim of this study was to elucidate the potential role of adipocyte precursor cells (preadipocytes/stromal vascular cells [SVC]

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Understanding the mechanisms supporting tumor-initiating cells (TIC) is vital to combat advanced stage recurrent cancers. Here we show that in advanced ovarian cancers NF-kB signaling via the RelB transcription factor supports TIC populations by directly regulating the cancer stem-like associated enzyme aldehyde dehydrogenase (ALDH). Loss of RelB significantly inhibited spheroid formation, ALDH expression and activity, chemoresistance, and tumorigenesis in subcutaneous and intrabursal mouse xenograft models of human ovarian cancer. RelB also affected expression of the ALDH gene ALDH1A2. Interestingly, classical NF-kB signaling through the RelA transcription factor was equally important for tumorigenesis in the intrabursal model, but had no effect on ALDH. In this case, classical signaling via RelA was essential for proliferating cells, whereas the alternative signaling pathway was not. Our results show how NF-kB sustains diverse cancer phenotypes via distinct classical and alternative signaling pathways, with implications for improved understanding of disease recurrence and therapeutic response.

Although histone H3 lysine 27 trimethylation (H3K27Me3) is associated with gene silencing, whether H3K27Me3 demethylation affects transcription and cell differentiation in vivo has remained elusive. To investigate this, we conditionally inactivated the two H3K27Me3 demethylases, Jmjd3 and Utx, in non-dividing intrathymic CD4+ T-cell precursors. Here we show that both enzymes redundantly promote H3K27Me3 removal at, and expression of, a specific subset of genes involved in terminal thymocyte differentiation, especially S1pr1, encoding a sphingosine-phosphate receptor required for thymocyte egress. Thymocyte expression of S1pr1 was not rescued in Jmjd3- and Utx-deficient male mice, which carry the catalytically inactive Utx homolog Uty, supporting the conclusion that it requires H3K27Me3 demethylase activity. These findings demonstrate that Jmjd3 and Utx are required for T-cell development, and point to a requirement for their H3K27Me3 demethylase activity in cell differentiation.

Innate lymphoid cells (ILCs) play important functions in immunity and tissue homeostasis, but their development is poorly understood. Through the use of single-cell approaches, we examined the transcriptional and functional heterogeneity of ILC progenitors and studied the precursor–product relationships that linked the subsets identified. This analysis identified two successive stages of ILC development within TCF-1 + early innate lymphoid progenitors (EILPs), which we named ‘specified EILPs’ and ‘committed EILPs’. Specified EILPs generated dendritic cells, whereas this potential was greatly decreased in committed EILP. TCF-1 was dispensable for the generation of specified EILPs, but required for the generation of committed EILPs. TCF-1 used a pre-existing regulatory landscape established in upstream lymphoid precursors to bind chromatin in EILPs. Our results provide insight into the mechanisms by which TCF-1 promotes developmental progression of ILC precursors, while constraining their dendritic cell lineage potential and enforcing commitment to ILC fate.