Tomato represents an important source of fiber and nutrients in the human diet and is a central model for the study of fruit biology. To identify components of fruit metabolic composition, here we have phenotyped tomato introgression lines (ILs) containing chromosome segments of a wild species in the genetic background of a cultivated variety. Using this high-diversity population, we identify 889 quantitative fruit metabolic loci and 326 loci that modify yield-associated traits. The mapping analysis indicates that at least 50% of the metabolic loci are associated with quantitative trait loci (QTLs) that modify whole-plant yield-associated traits. We generate a cartographic network based on correlation analysis that reveals whole-plant phenotype associated and independent metabolic associations, including links with metabolites of nutritional and organoleptic importance. The results of our genomic survey illustrate the power of genome-wide metabolic profiling and detailed morphological analysis for uncovering traits with potential for crop breeding.

We have conducted a comprehensive metabolic profiling on tomato (Lycopersicon esculentum) leaf and developing fruit tissue using a recently established gas chromatography-mass spectrometry profiling protocol alongside conventional spectrophotometric and liquid chromatographic methodologies. Applying a combination of these techniques, we were able to identify in excess of 70 small-M r metabolites and to catalogue the metabolite composition of developing tomato fruit. In addition to comparing differences in metabolite content between source and sink tissues of the tomato plant and after the change in metabolite pool sizes through fruit development, we have assessed the influence of hexose phosphorylation through fruit development by analyzing transgenic plants constitutively overexpressing Arabidopsis hexokinase AtHXK1. Analysis of the total hexokinase activity in developing fruits revealed that both wild-type and transgenic fruits exhibit decreasing hexokinase activity with development but that the relative activity of the transgenic lines with respect to wild type increases with development. Conversely, both point-by-point and principal component analyses suggest that the metabolic phenotype of these lines becomes less distinct from wild type during development. In summary, the data presented in this paper demonstrate that the influence of hexose phosphorylation diminishes during fruit development and highlights the importance of greater temporal resolution of metabolism.Hexokinase (E.C. 2.7.1.1) catalyzes the phosphorylation of hexoses to form hexose monophosphates. This reaction is especially important in plants because the use of free phosphates is particularly complex in higher plants ( Kruger, 1997). There have been many reports on the presence of glucokinase and hexokinase enzymes in a wide variety of plant species including tomato (Lycopersicon esculentum; Martinez-Barajaz and Randall, 1998), maize (Zea mays; Doehlert, 1989;Schnarrenberger, 1990; Galina et al., 1995), potato (Solanum tuberosum; Renz and Stitt, 1993;Veramendi et al., 1999), pea (Pisum sativum; Turner et al., 1977;Turner and Copeland, 1981) Recently, transgenic manipulations of the activity of hexokinase have been carried out in tomato, potato, and Arabidopsis (Jang et al., 1997; Dai et al., 1999;Veramendi et al., 1999Veramendi et al., , 2002. The results of these manipulations varied greatly between species. Transgenic Arabidopsis seeds that exhibited decreased or increased activities of hexokinase 1 displayed hyposensitive or hypersensitive responses to growth on high (6% [w/v]) Glc containing agar (Jang et al., 1997). The authors concluded that the hexokinase protein acts as a sensor for Glc in an analogous manner to those operating in yeast (Saccharomyces cerevisiae) and that the modulation in the abundance of this sensor led to changes in gene expression that were responsible for the phenotype observed. The overexpression of this Arabidopsis hexokinase isoform in tomato plants led to growth inhibition, reduced photosynthesis, and a...

Key Points• IFNa targets Jak2V617F MPN stem cells.Interferon-a (IFNa) is an effective treatment of patients with myeloproliferative neoplasms (MPNs). In addition to inducing hematological responses in most MPN patients, IFNa reduces the JAK2V617F allelic burden and can render the JAK2V617F mutant clone undetectable in some patients. The precise mechanism underlying these responses is incompletely understood and whether the molecular responses that are seen occur due to the effects of IFNa on JAK2V617F mutant stem cells is debated. Using a murine model of Jak2V617F MPN, we investigated the effects of IFNa on Jak2V617F MPN-propagating stem cells in vivo. We report that IFNa treatment induces hematological responses in the model and causes depletion of Jak2V617F MPN-propagating cells over time, impairing disease transplantation. We demonstrate that IFNa treatment induces cell cycle activation of Jak2V617F mutant long-term hematopoietic stem cells and promotes a predetermined erythroid-lineage differentiation program. These findings provide insights into the differential effects of IFNa on Jak2V617F mutant and normal hematopoiesis and suggest that IFNa achieves molecular remissions in MPN patients through its effects on MPN stem cells. Furthermore, these results support combinatorial therapeutic approaches in MPN by concurrently depleting dormant JAK2V617F MPNpropagating stem cells with IFNa and targeting the proliferating downstream progeny with JAK2 inhibitors or cytotoxic chemotherapy. (Blood. 2013;121(18):3692-3702)

Selective targeting of BCL2 with the BH3-mimetic venetoclax is proving transformative for patients with various leukemias. TP53 controls apoptosis upstream from where BCL2 and its pro-survival relatives, such as MCL1, act. Therefore, targeting these pro-survival proteins could trigger apoptosis across diverse blood cancers, irrespective of TP53 mutation status. Indeed, targeting BCL2 has produced clinically relevant responses in blood cancers with aberrant TP53. However, we show that TP53 mutated or deficient myeloid and lymphoid leukemias outcompete isogenic controls with intact TP53, unless sufficient concentrations of BH3-mimetics targeting BCL2 or MCL1 are applied. Strikingly, tumor cells with TP53 dysfunction escape and thrive over time if inhibition of BCL2 or MCL1 is sub-lethal, in part because of an increased threshold for BAX/BAK activation in these cells. Our study reveals the key role of TP53 in shaping long-term responses to BH3-mimetic drugs and reconciles the disparate pattern of initial clinical response to venetoclax, followed by subsequent treatment failure among patients with TP53-mutant chronic lymphocytic leukemia (CLL) or acute myeloid leukemia (AML). In contrast to BH3-mimetics targeting just BCL2 or MCL1 at doses which are individually sub-lethal, we find that a combined BH3-mimetic approach targeting both pro-survival proteins enhances lethality and durably suppresses leukemic burden, regardless of TP53 mutation status. Our findings highlight the importance of employing sufficiently lethal treatment strategies to maximize outcomes for patients with TP53-mutant disease. In addition, our findings caution against use of sub-lethal BH3-mimetic drug regimens, which may enhance the risk of disease progression driven by emergent TP53 mutant clones.

Natural killer (NK) cells are naturally circulating innate lymphoid cells that protect against tumor initiation and metastasis and contribute to immunopathology during inflammation. The signals that prime NK cells are not completely understood, and, although the importance of IFN type I is well recognized, the role of type III IFN is comparatively very poorly studied. IL-28R-deficient mice were resistant to LPS and cecal ligation puncture-induced septic shock, and hallmark cytokines in these disease models were dysregulated in the absence of IL-28R. IL-28R-deficient mice were more sensitive to experimental tumor metastasis and carcinogen-induced tumor formation than WT mice, and additional blockade of interferon alpha/beta receptor 1 (IFNAR1), but not IFN-γ, further enhanced metastasis and tumor development. IL-28R-deficient mice were also more susceptible to growth of the NK cell-sensitive lymphoma, RMAs. Specific loss of IL-28R in NK cells transferred into lymphocyte-deficient mice resulted in reduced LPS-induced IFN-γ levels and enhanced tumor metastasis. Therefore, by using IL-28R-deficient mice, which are unable to signal type III IFN-λ, we demonstrate for the first time, to our knowledge, the ability of IFN-λ to directly regulate NK cell effector functions in vivo, alone and in the context of IFN-αβ.IL-28R | NK cells | anti-tumor | interferon | LPS

SUMMARY Acute myeloid leukemia (AML) is an aggressive and lethal blood cancer maintained by rare populations of leukemia stem cells (LSCs). Selective targeting of LSCs is a promising approach for treating AML and preventing relapse following chemotherapy, and developing such therapeutic modalities is a key priority. Here, we show that targeting telomerase activity eradicates AML LSCs. Genetic deletion of the telomerase subunit Terc in a retroviral mouse AML model induces cell cycle arrest and apoptosis of LSCs, and depletion of telomerase-deficient LSCs is partially rescued by p53 knockdown. Murine Terc−/− LSCs express a specific gene expression signature that can be identified in human AML patient cohorts and is positively correlated with patient survival following chemotherapy. In xenografts of primary human AML, genetic or pharmacological inhibition of telomerase targets LSCs, impairs leukemia progression, and delays relapse following chemotherapy. Together, these results establish telomerase inhibition as an effective strategy for eliminating AML LSCs.

Bone-marrow adipogenesis is an aging-related phenomenon and is correlated with osteoporosis. The latter is a prevalent bone disease in the elderly leading to increased fracture risk and mortality. It is widely hypothesized that the underlying molecular mechanism includes a shift in the commitment of mesenchymal stem cells (MSCs) from the osteogenic lineage to the adipogenic lineage. Lineage skewing is at least partially a result of transcriptional changes. The nuclear transcription factor peroxisome proliferator-activated receptor c (PPAR-c) has been proposed as a major decision factor in MSC lineage commitment, promoting adipogenesis at the expense of osteogenesis. Here we found that PPAR-c acted unexpectedly to stimulate osteoblast differentiation from human bone marrowderived MSCs. Both rosiglitazone-mediated activation and overexpression of PPAR-c caused acceleration of osteoblast differentiation. Conversely, shRNAi-mediated PPARc knockdown diminished osteoblast differentiation. MSCs that were treated with rosiglitazone did not preferentially differentiate into adipocytes. However, the rosiglitazonemediated acceleration of osteoblast differentiation was followed by increased accumulation of reactive oxygen species and apoptosis. In contrast to the osteogenic lineage, cells of the adipogenic lineage were protected from this. Our data support a new concept on bone health that adds to the explanation of the clinically observed suppressive action of activated PPAR-c on bone and the associated phenomenon of bone marrow adipogenesis. This concept is based on a higher susceptibility of the osteogenic than the adipogenic lineage to oxidative stress and apoptosis that is preferentially triggered in the osteoblasts by activated PPAR-c. STEM CELLS 2010;28:916-927 Disclosure of potential conflicts of interest is found at the end of this article.

This unit describes basic techniques in human mesenchymal stem cell (hMSC) cultures. It includes protocols for the differentiation of hMSCs into osteogenic and adipogenic lineages, genetic perturbations, and phenotypic analyses. hMSCs can be differentiated with dexamethasone and β‐glycerophosphate into mineralizing osteoblasts within 2 to 3 weeks, or with dexamethasone, indomethacin, and 3‐isobutyl‐1‐methylxanthine into lipid vesicle–containing adipocytes within 1 to 2 weeks. Phenotypic changes during those highly dynamic differentiation processes can be detected by biochemical and histological assays and gene expression analyses of differentiation markers. In addition, this unit describes an electroporation method that allows the transient genetic perturbation of hMSCs. Curr. Protoc. Stem Cell Biol. 17:1H.3.1‐1H.3.20. © 2011 by John Wiley & Sons, Inc.