The Eμ-Myc mouse is an extensively used model of MYC driven malignancy; however to date there has only been partial characterization of MYC co-operative mutations leading to spontaneous ...lymphomagenesis. Here we sequence spontaneously arising Eμ-Myc lymphomas to define transgene architecture, somatic mutations, and structural alterations. We identify frequent disruptive mutations in the PRC1-like component and BCL6-corepressor gene Bcor. Moreover, we find unexpected concomitant multigenic lesions involving Cdkn2a loss and other cancer genes including Nras, Kras and Bcor. These findings challenge the assumed two-hit model of Eμ-Myc lymphoma and demonstrate a functional in vivo role for Bcor in suppressing tumorigenesis.
Display omitted
► A bioinformatic approach has been used to predict the exportome of Babesia bovis. ► A subset of proteins that are likely to be exported into parasite-infected red blood cells have ...been identified. ► Previously unknown proteins in B. bovis-infected red blood cells have been identified and localised.
Babesia bovis is a pathogen of considerable economic significance to the livestock industry worldwide but the precise mechanisms by which this parasite causes disease in susceptible cattle remain poorly understood. It is clear, however, that alterations to the structure and function of red blood cells in which the parasites reside and replicate play an important role in pathogenesis and that these are secondary to the export of numerous, currently unknown and uncharacterised parasite-encoded proteins. Using a rational bioinformatic approach, we have identified a set of 362 proteins (117 of which are hypothetical) that we predict encompasses the B. bovis exportome. These exported proteins are likely to be trafficked to various cellular locations, with a subset destined for the red blood cell cytosol or the red blood cell cytoskeleton. These proteins are likely to play important roles in mediating the pathogenesis of babesiosis. We have selected three novel proteins and confirmed their predicted export and localisation within the host red blood cell by immunofluorescence using specific antibodies raised against these proteins. Complete characterisation of these novel exported parasite proteins will help elucidate their function within the host red blood cell and assist in identification of new therapeutic targets for babesiosis.
E proteins and their antagonists, the Id proteins, are transcriptional regulators important for normal hematopoiesis. We found that Id2 acts as a key regulator of leukemia stem cell (LSC) potential ...in MLL-rearranged acute myeloid leukemia (AML). Low endogenous Id2 expression is associated with LSC enrichment while Id2 overexpression impairs MLL-AF9-leukemia initiation and growth. Importantly, MLL-AF9 itself controls the E-protein pathway by suppressing Id2 while directly activating E2-2 expression, and E2-2 depletion phenocopies Id2 overexpression in MLL-AF9-AML cells. Remarkably, Id2 tumor-suppressive function is conserved in t(8;21) AML. Low expression of Id2 and its associated gene signature are associated with poor prognosis in MLL-rearranged and t(8;21) AML patients, identifying the Id2/E-protein axis as a promising new therapeutic target in AML.
Display omitted
•MLL-AF9 co-ordinately downregulates Id2 and upregulates E2-2 expression•Id2 functions as a negative regulator of LSC potential in MLL-rearranged AML•Id2 overexpression or E2-2 knockdown suppresses MLL-rearranged and t(8;21) AML•Id2-associated gene signature correlates with prognosis in AML patients
Ghisi et al. show that MLL-AF9 reduces Id2 and increases E2-2 expression to drive and sustain leukemia stem cell potential in MLL-rearranged acute myeloid leukemia (AML). Low expression of Id2 or of an Id2 gene signature is associated with poor prognosis in not only MLL-rearranged but also t(8;21) AML patients.
Targeted gene disruption has proved to be a powerful approach for studying the function of important ligands involved in erythrocyte invasion by the extracellular merozoite form of the human malaria ...parasite, Plasmodium falciparum. Merozoite invasion proceeds via a number of seemingly independent alternate pathways, such that entry can proceed with parasites lacking particular ligand-receptor interactions. To date, most focus in this regard has been on single-pass (type 1) membrane proteins that reside in the secretory organelles. Another class of merozoite proteins likely to include ligands for erythrocyte receptors are the glycosylphosphatidyl inositol (GPI)-anchored membrane proteins that coat the parasite surface and/or reside in the apical organelles. Several of these are prominent vaccine candidates, although their functions remain unknown. Here, we systematically attempted to disrupt the genes encoding seven of the known GPI-anchored merozoite proteins of P. falciparum by using a double-crossover gene-targeting approach. Surprisingly, and in apparent contrast to other merozoite antigen classes, most of the genes (six of seven) encoding GPI-anchored merozoite proteins are refractory to genetic deletion, with the exception being the gene encoding merozoite surface protein 5 (MSP-5). No distinguishable growth rate or invasion pathway phenotype was detected for the msp-5 knockout line, although its presence as a surface-localized protein was confirmed.
Malaria is caused by four species of apicomplexan protozoa belonging to the genus Plasmodium. These parasites possess a specialized collection of secretory organelles called rhoptries, micronemes and ...dense granules (DGs) that in part facilitate invasion of host cells. The mechanism by which the parasite traffics proteins to these organelles as well as regulates their secretion has important implications for understanding the invasion process and may lead to development of novel intervention strategies. In this review, we focus on emerging data about trafficking signals, mechanisms of biogenesis and secretion. At least some of these are conserved in higher eukaryotes, suggesting that rhoptries, micronemes and DGs are related to organelles such as secretory lysosomes that are well known to mainstream cell biologists.
Identification of metabolic pathways that are dysregulated in acute myeloid leukaemia (AML) offers significant promise for the development of new therapeutic strategies. Heme is an essential ...metabolite with broad biological activity that is required and produced by all cells. In addition to its catalytic role as a cofactor in hemoproteins, heme also directly regulates signalling and gene expression. We and others have shown that heme biosynthesis enzymes are among the most downregulated genes during AML progression; and large-scale CRISPR screening studies have revealed that AML cells have an increased dependence on the expression of pathway components. We analysed heme biosynthesis in mouse models, AML cell lines and patient samples and found that common AML driver genes cause reduced heme production capacity in leukaemic cells. The low heme state in turn affects mitochondrial metabolism and drives altered gene expression patterns, in part via heme sensing transcription factors including BACH1. In proof-of concept experiments we demonstrate that low heme AML cells have increased sensitivity to inhibitors of the electron transport chain and drugs that induce ferroptosis. Using unbiased CRISPR screening methodologies we are now uncovering novel biochemical pathways that are synthetic lethal with heme metabolism. Altogether, our data points to a model where low heme biosynthesis promotes metabolic and transcriptional programs that are beneficial for self-renewal but also result in vulnerabilities that can be exploited for therapeutic benefit.
Plasmodium parasites have three sets of specialised secretory organelles at the apical end of their invasive forms – rhoptries, micronemes and dense granules. The contents of these organelles are ...responsible for or contribute to host cell invasion and modification, and at least four apical proteins are leading vaccine candidates. Given the unusual nature of
Plasmodium invasion, it is not surprising that unique proteins are involved in this process. Nowhere is this more evident than in rhoptries. We have collated data from several recent studies to compile a rhoptry proteome. Discussion is focussed here on rhoptry content and function.
The pathological consequences of malaria infection are the result of parasite replication within red blood cells (RBCs). Invasion into RBCs is mediated by a large repertoire of parasite proteins that ...are distributed on the parasite surface and within specialised apical secretory organelles. As invasion is an essential step in the parasite life-cycle, targeting invasion-related molecules provides an avenue for therapeutic intervention. We have used genome and transcriptome data available for
Plasmodium falciparum to identify proteins likely to be involved in RBC invasion. Of these candidates, we selected a protein which we have dubbed PfRON6 for detailed characterisation. PfRON6 contains a novel cysteine-rich domain that is conserved in other Apicomplexan parasites. We show that PfRON6 is localised in the rhoptry neck of merozoites and is transferred to the newly formed parasitophorous vacuole during invasion. Transfection experiments indicate that the gene which encodes PfRON6 is refractory to integration that disrupts the coding sequence, suggesting its absence is incompatible with the parasite life-cycle. Further, the cysteine-rich domain appears to be functionally important as it cannot be truncated. Taken together, these data identify PfRON6 as a novel and potentially important component of the
Plasmodium invasion machinery.
PDF
