C/EBP alpha and GATA-2 Mutations Induce Bilineage Acute Erythroid Leukemia through Transformation of a Neomorphic Neutrophil-Erythroid Progenitor

Acute erythroid leukemia (AEL) commonly involves both myeloid and erythroid lineage transformation. However, the mutations that cause AEL and the cell(s) that sustain the bilineage leukemia phenotype remain unknown. We here show that combined biallelic Cebpa and Gata2 zinc finger-1 (ZnF1) mutations cooperatively induce bilineage AEL, and that the major leukemia-initiating cell (LIC) population has a neutrophil-monocyte progenitor (NMP) phenotype. In pre-leukemic NMPs Cebpa and Gata2 mutations synergize by increasing erythroid transcription factor (TF) expression and erythroid TF chromatin access, respectively, thereby installing ectopic erythroid potential. This erythroid-permissive chromatin conformation is retained in bilineage LICs. These results demonstrate that synergistic transcriptional and epigenetic reprogramming by leukemia-initiating mutations can generate neomorphic pre-leukemic progenitors, defining the lineage identity of the resulting leukemia

Characterising early human lympho-myeloid haematopoietic progenitors and their relationship with acute myeloid leukaemia stem cells

Haematopoiesis is a quintessential cellular hierarchy, with the haematopoietic stem cell having the ability to produce all blood cells. Downstream of the stem cell are multiple progenitor populations with increasing lineage-restriction. However, our knowledge of the progenitors that produce the lymphoid and myeloid lineages remains incomplete. Furthermore, in acute myeloid leukaemia there is a differentiation arrest at the lympho-myeloid progenitor stage, with the development of a progenitor-like leukaemia stem cells. A thorough comparison of the progenitor-like leukaemia stem cell with normal stem and progenitor cells is yet to be completed. Presented here is a comprehensive study of the lympho-myeloid progenitors in both normal and leukaemic haematopoiesis. Firstly, the normal lympho-myeloid progenitors were fully characterised, both functionally and transcriptionally. Extensive single-cell analysis allowed the heterogeneity and continuum underlying lympho-myeloid differentiation to be uncovered. Although the majority of single-cells generated only one mature lineage, rare multi-lineage single-cells were detected. The lympho-myeloid progenitors were then studied in acute myeloid leukaemia. It was demonstrated that there is often an expansion of the lympho-myeloid progenitors, which develop leukaemia-propagating ability. Transcriptionally, it was seen that the leukaemia stem cells displayed dysregulated expression profiles, whilst retaining some resemblance to the normal progenitors. A set of genes upregulated in the leukaemia stem cell was identified, and it was proposed that six of these genes may play a role in leukaemogenesis. Studying both normal and leukaemic haematopoiesis is essential in advancing the treatment of acute myeloid leukaemia. Firstly, a more thorough understanding of the process of normal lympho-myeloid differentiation may aid the development of differentiation therapies. Secondly, by identifying functionally relevant markers of the leukaemia stem cell, treatments targeting the apex of the leukaemic hierarchy may be developed. And through the eradication of the leukaemia stem cell, we may truly eliminate the leukaemic disease.</p

Fast and slow inhibition in the visual thalamus is influenced by allocating GABAA receptors with different gamma subunits

Cell-type specific differences in the kinetics of inhibitory postsynaptic conductance changes (IPSCs) are believed to impact upon network dynamics throughout the brain. Much attention has focused on how GABAA receptor (GABAAR) α and β subunit diversity will influence IPSC kinetics, but less is known about the influence of the γ subunit. We have examined whether GABAAR γ subunit heterogeneity influences IPSC properties in the thalamus. The γ2 subunit gene was deleted from GABAARs selectively in the dorsal lateral geniculate nucleus (dLGN). The removal of the γ2 subunit from the dLGN reduced the overall spontaneous IPSC (sIPSC) frequency across all relay cells and produced an absence of IPSCs in a subset of relay neurons. The remaining slower IPSCs were both insensitive to diazepam and zinc indicating the absence of the γ2 subunit. Because these slower IPSCs were potentiated by methyl-6,7-dimethoxy-4-ethyl-β-carboline-3-carboxylate (DMCM), we propose these IPSCs involve γ1 subunit-containing GABAAR activation. Therefore, γ subunit heterogeneity appears to influence the kinetics of GABAAR-mediated synaptic transmission in the visual thalamus in a cell-selective manner. We suggest that activation of γ1 subunit-containing GABAARs give rise to slower IPSCs in general, while faster IPSCs tend to be mediated by γ2 subunit-containing GABAARs

C/EBPα and GATA-2 mutations induce bilineage acute erythroid leukemia through transformation of a neomorphic neutrophil-erythroid progenitor

Acute erythroid leukemia (AEL) commonly involves both myeloid and erythroid lineage transformation. However, the mutations that cause AEL and the cell(s) that sustain the bilineage leukemia phenotype remain unknown. We here show that combined biallelic Cebpa and Gata2 zinc finger-1 (ZnF1) mutations cooperatively induce bilineage AEL, and that the major leukemia-initiating cell (LIC) population has a neutrophil-monocyte progenitor (NMP) phenotype. In pre-leukemic NMPs Cebpa and Gata2 mutations synergize by increasing erythroid transcription factor (TF) expression and erythroid TF chromatin access, respectively, thereby installing ectopic erythroid potential. This erythroid-permissive chromatin conformation is retained in bilineage LICs. These results demonstrate that synergistic transcriptional and epigenetic reprogramming by leukemia-initiating mutations can generate neomorphic pre-leukemic progenitors, defining the lineage identity of the resulting leukemia

Single-cell analysis reveals the continuum of human lympho-myeloid progenitor cells.

The hierarchy of human hemopoietic progenitor cells that produce lymphoid and granulocytic-monocytic (myeloid) lineages is unclear. Multiple progenitor populations produce lymphoid and myeloid cells, but they remain incompletely characterized. Here we demonstrated that lympho-myeloid progenitor populations in cord blood - lymphoid-primed multi-potential progenitors (LMPPs), granulocyte-macrophage progenitors (GMPs) and multi-lymphoid progenitors (MLPs) - were functionally and transcriptionally distinct and heterogeneous at the clonal level, with progenitors of many different functional potentials present. Although most progenitors had the potential to develop into only one mature cell type ('uni-lineage potential'), bi- and rarer multi-lineage progenitors were present among LMPPs, GMPs and MLPs. Those findings, coupled with single-cell expression analyses, suggest that a continuum of progenitors execute lymphoid and myeloid differentiation, rather than only uni-lineage progenitors' being present downstream of stem cells.MRC (MHU Award G1000729, MRC Disease Team Award 4050189188), CRUK (Program Grant to PV C7893/A12796, CRUK program grant to BG C1163/A21762), Bloodwise (Specialist Program 13001 and Project grant to 12019), an MRC PhD studentship (F.H. & Z.A.), The MRC Single Cell Award (MR/M00919X/1) to the WIMM and the Oxford Partnership Comprehensive Biomedical Research Centre (NIHR BRC Funding scheme). We thank the High-Throughput Genomics Group at the Wellcome Trust Centre for Human Genetics (funded by Wellcome Trust grant reference 090532/Z/09/Z) for generation of sequencing data. R.M. was supported by National Institutes of Health grants R01CA188055 and U01HL099999, New York Stem Cell Foundation Robertson Investigator and Leukemia and Lymphoma Society Scholar Award. A.R. was supported by an Erwin-Schroedinger Research fellowship from the Austrian Science Fund (FWF)