Zeb1 modulates hematopoietic stem cell fates required for suppressing acute myeloid leukemia

Zeb1, a zinc finger E-box binding homeobox epithelial-mesenchymal (EMT) transcription factor, confers properties of ‘stemness’, such as self-renewal, in cancer. Yet little is known about the function of Zeb1 in adult stem cells. Here, we used the hematopoietic system, as a well-established paradigm of stem cell biology, to evaluate Zeb1 mediated regulation of adult stem cells. We employed a conditional genetic approach using the Mx1-Cre system to specifically knockout (KO) Zeb1 in adult hematopoietic stem cells (HSCs) and their downstream progeny. Acute genetic deletion of Zeb1 led to rapid onset thymic atrophy and apoptosis driven loss of thymocytes and T cells. A profound cell-autonomous self-renewal defect and multi-lineage differentiation block was observed in Zeb1 KO HSCs. Loss of Zeb1 in HSCs activated transcriptional programs of deregulated HSC maintenance and multi-lineage differentiation genes, and of cell polarity, consisting of cytoskeleton, lipid metabolism/lipid membrane and cell adhesion related genes. Notably, Epithelial cell adhesion molecule (EpCAM) expression was prodigiously upregulated in Zeb1 KO HSCs, which correlated with enhanced cell survival, diminished mitochondrial metabolism, ribosome biogenesis, and differentiation capacity and an activated transcriptomic signature associated with acute myeloid leukemia (AML) signaling. ZEB1 expression was downregulated in AML patients and Zeb1 KO in the malignant counterparts of HSCs - leukemic stem cells (LSCs) - accelerated MLL-AF9 and Meis1a/Hoxa9-driven AML progression, implicating Zeb1 as a tumor suppressor in AML LSCs. Thus, Zeb1 acts as a transcriptional regulator in hematopoiesis, critically co-ordinating HSC self-renewal, apoptotic and multi-lineage differentiation fates required to suppress leukemic potential in AML

Hypercholesteremia as a regulator in haematopoiesis and leukaemic stem cells in acute myeloid leukaemia

Accumulating evidence suggests an emerging association between perturbed haematopoiesis, development of leukaemia and cardiovascular disease in the context of a high-fat western diet. To explore this subject, I investigated the role of atherosclerosis prone low-density lipid receptor (Ldlr) in normal and leukaemic haematopoiesis and the impact of a high-fat diet (HFD) or normal chow diet (ND) in this setting. In steady-state, under normal dietary conditions, mice engineered to be deficient in the LDL receptor (Ldlr-/-) had increased numbers of haematopoietic stem cells (HSCs), which was associated with increased cell cycling and an increase in inflammatory cytokines and chemokines. In Ldlr-/- mice bone marrow differentiation, as assessed by the CFC assay, was decreased while paradoxically white blood cells were increased which mapped to CD4+ T cell and monocyte increases in the peripheral blood. To induce hypercholesteremia and atherosclerosis, Ldlr-/- mice were fed a HFD and the attendant impact on haematopoiesis was evaluated. A significant increase in HSCs and associated early progenitor compartments (HSPCs) was noted in Ldlr-/- mice fed HFD alongside an increase in committed progenitor cells of both the myeloid and lymphoid lineage. As expected, inflammatory immune cell subsets were increased together with increases in platelets and alterations in regulatory immune cells in Ldlr-/- mice fed HFD. HSCs from Ldlr-/- mice fed HFD performed poorly in functional analysis, as judged by competitive transplantation, displaying significant multi-lineage differentiation defects. Underpinning these defects, RNA-seq analysis revealed altered apoptosis, inflammation, lipid metabolism pathways, RNA biology, and AML enriched gene pathways in HSCs from Ldlr-/- mice fed a HFD. These molecular pathways mapped not only to haematological disease, like AML, and cardiovascular disease, but also nephrotoxicity and hepatoxicity, highlighting the widespread impact of perturbed haematopoiesis induced by HFD and atherosclerosis. Unexpectedly, we found that MLL-AF9 transformed HSPCs from Ldlr-/- mice fed a HFD developed AML later than their ND counterparts, but this was likely reflected by a delayed migration of leukaemic blast cells from BM to PB. This argument was supported by altered adhesion protein expression in human MLL-AF9 AML cell lines exposed to atherogenic lipoproteins in vitro. Decreased markers of immune recognition were also observed in human MLL-AF9 AML cell lines exposed to atherogenic lipoproteins in vitro. The data provided in this thesis provide mechanistic vi insights into how HFD epigenetically disrupts HSC function and haematopoiesis in the setting of atherosclerosis, and it provides a starting point to further explore relationship between HFD, atherosclerosis and how perturbed haematopoiesis can lead to AML

Spinal gout mimicking paraspinal abscess: A case report

Gout is usually thought of as a peripheral joint disease. However, case reports are available describing gouty lesions in the spine. We report a case of a 51 year old African American woman with no previous history of gout who presented with lower back pain and fever and was found to have multiple small fluid collections in the paraspinal muscles at the L3 to L5 levels on the MRI. She was empirically treated with antibiotics, since the fluid was not accessible for drainage initially. Unsuccessful antibiotic therapy and an episode of peripheral gout during this hospitalization prompted the diagnosis of axial gout as the cause for the paraspinal lesions in this patient. CT guided aspiration of the paraspinal lesions confirmed monosodium urate (gout) crystals under polarized microscopy