Biology subjects

Ottersbach, K.

Publications and source records attributed to Ottersbach, K..

5 recordsLinked to original sources

bioRxiv2024

Leukaemia cell intrinsic and extrinsic factors cooperate to facilitate the survival and proliferation of KMT2A-rearranged B-ALL in the CNS niche.

Infant B-cell acute lymphoblastic leukaemia (B-ALL) is a rare, aggressive entity characterised by KMT2A rearrangements and poor outcomes. One of the unique features of KMT2A-rearranged infant ALL that contributes to these poor outcomes is a particularly high rate of central nervous system (CNS) involvement. There is a broad lack of understanding regarding the molecular processes and immune environment in CNS ALL. This hinders the development of targeted therapies for CNS ALL, which is increasingly essential given the potentially reduced efficacy of current immunotherapies in this specialised environment. In this study, we used an immune-competent KMT2A-AFF1+ infant B-ALL murine model to explore the cell-intrinsic and cell-extrinsic mechanisms that underpin this clinically significant complication. We show novel functional impacts on leukaemia propagating cells following exposure to the CNS niche which results in unique leukaemia repopulation dynamics. Transcriptomic and immune cell profiling by niche showed differences in the immune microenvironment between the CNS and bone marrow niches. The CNS niche demonstrates supressed T cell and macrophage activity which may be part of a wider CNS niche-specific immune escape mechanism. Our transcriptomic comparisons by niche also led us to explore the role of PI3K pathway activation in the propagation of leukaemia cells within the CNS niche. We identify miR-93 as a possible master regulator of this process. The importance of miR-93 is emphasised as it is shown to be upregulated in CNS leukaemia cells across multiple murine KMT2A-AFF1 B-ALL model systems and in primary KMT2A-AFF1 B-ALL patient samples. We conclude by showing impaired CNS engraftment of leukaemia cells upon miR-93 knockdown, cementing its importance in CNS leukaemia biology and opening up new CNS-specific therapeutic opportunities.

cancer biology↗

bioRxiv2023

A microRNA expression signature in infant t(4;11) MLL-AF4+ BCP-ALL uncovers novel therapeutic targets

Infants and children with MLL-AF4+ leukemia have an urgent need for more efficient and less aggressive therapy. In this study, we studied three microRNAs that are downregulated in MLL-AF4+ B-cell precursor acute lymphoblastic leukemia (BCP-ALL): miR-194, miR-99b and miR-125a-5p. When overexpressed, all three microRNAs impaired the survival of MLL-AF4+ leukemic blasts and the maintenance of MLL-AF4+ BCP-ALL. We identified microRNA target genes responsible for this phenotype that are upregulated in MLL-AF4+ BCP-ALL: CA5B, PPP3CA and PPP2R5C. Using CRISPR-Cas9 and specific inhibitors, we confirmed that CA5B, PPP3CA and PPP2R5C downregulation/inhibition severely compromised the proliferation and survival of MLL-AF4+ leukemic blasts. Importantly, CA5B, PPP3CA and PP2A inhibition by acetazolamide, tacrolimus and LB-100, respectively, showed high toxicity towards MLL-AF4+ leukemic blasts and reduced leukemia burden in vivo. This study highlights how the unique microRNA expression signature of patients with MLL-AF4+ BCP-ALL can be used to uncover novel therapeutic avenues and accelerate drug repurposing. Statement of significanceThere is an urgent need to identify novel therapeutic avenues for patients with MLL-AF4+ BCP-ALL that are more effective and less aggressive. This study identified three clinically available drugs (acetazolamide, tacrolimus and LB-100) with high and selective toxicity towards MLL-AF4+ leukemic cells.

cancer biology↗

bioRxiv2021

Endothelial-specific Gata3 expression is required for haematopoietic stem cell generation

To generate sufficient numbers of transplantable haematopoietic stem cells (HSCs) in vitro, a detailed understanding of how this process takes place in vivo is essential. The endothelial-to-haematopoietic transition (EHT), which culminates in the production of the first HSCs, is a highly complex process during which key regulators are switched on and off at precise moments and which is embedded into a myriad of microenvironmental signals from surrounding cells and tissues. We have previously demonstrated an HSC-supportive function for Gata3 within the sympathetic nervous system and the sub-aortic mesenchyme, but show here that it also plays a cell-intrinsic role during the EHT. It is expressed in haemogenic endothelial cells and early HSC precursors, where its expression correlates with a more quiescent state. Importantly, endothelial-specific deletion of Gata3 shows that it is functionally required for these cells to mature into HSCs, placing Gata3 at the core of the EHT regulatory network.

developmental biology↗

bioRxiv2021

p57Kip2 regulates embryonic haematopoietic stem cell numbers by controlling the size of the sympathoadrenal progenitor pool

Haematopoietic stem cells (HSCs) are of major clinical importance, and finding methods for their in vitro generation is a prime research focus. We demonstrate that the cell cycle inhibitor p57Kip2/Cdkn1c limits HSC numbers by restricting the size of the sympathetic nervous system (SNS) and the amount of HSC-supportive catecholamines secreted by these cells, specifically in the aorta-gonads-mesonephros (AGM) region via {beta}2-adrenergic receptor signalling. This regulation occurs at the SNS progenitor level and is in contrast to the cell-intrinsic function of p57Kip2 in maintaining adult HSCs. Using single-cell RNA-Seq we dissect the differentiation pathway of neural crest cells into SNS cells in the AGM and reveal that they are able to take an alternative differentiation pathway, giving rise to a subset of mesenchymal cells expressing HSC-supportive factors. Neural crest cells thus appear to contribute to the AGM HSC niche via two different mechanisms: SNS-mediated catecholamine secretion and HSC-supportive mesenchymal cell production.

developmental biology↗

bioRxiv2019

Single cell transcriptome analysis reveals markers of naive and lineage-primed hematopoietic progenitors derived from human pluripotent stem cells.

During embryogenesis the hematopoietic system develops through distinct waves that generate progenitors with increasing lineage potential, ultimately producing haematopoietic stem cells (HSCs). In vitro differentiation of human pluripotent stem cells (hPSCs) follows the early steps of haematopoietic development but the production of HSCs has proven more challenging. To study the dynamics and heterogeneity of hematopoietic progenitor cells generated in vitro from hPSCs, we performed RNA sequencing of over 10000 CD235a-CD43+single cells. We identified the transcriptome of naive progenitors and those primed toward erythroid, megakaryocyte and leukocyte lineages, and revealed their markers by clustering, trajectory analyses and functional assays. CD44 marks naive clonogenic progenitors that express the transcription factor, LMO4 and can be expanded upon BMP4 stimulation. Naive progenitors give rise to primed CD326+erythroid, ICAM2+CD9+megakaryocyte, and monocyte, neutrophil and eosinophil progenitors. We have generated an online dataset of human hematopoietic progenitors and their transcriptional remodelling upon lineage priming.

developmental biology↗