Biology subjects

Nitsche, L.

Publications and source records attributed to Nitsche, L..

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

Does meiotic drive alter male mate preference?

Male mate preferences have been demonstrated across a range of species, including the Malaysian stalk-eyed fly, Teleopsis dalmanni. This species is subject to SR, an X-linked male meiotic driver, that causes the dysfunction of Y-sperm and the production all female broods. SR is associated with a low frequency inversion spanning most of the X chromosome that causes reduced organismal fitness. While there has been work considering female avoidance of meiotic drive males, the mating decisions of drive-bearing males have not been considered previously. As drive males are of lower genetic quality they may be less able to bear the cost of choice or may experience weaker selection for its maintenance if they are avoided by females. We investigated preference of drive males using binary choice trials. We confirmed that males prefer to mate with large females (indicative of greater fecundity) but found no evidence that the strength of male mate preference differs between drive and standard males. This suggests that the cost of choice does not restrict male reference among drive males. In a further experiment, we found that large eyespan males showed strong preference whereas small eyespan males showed no preference. This is likely to weaken mate preference in drive males, as on average they have reduced eyespan compared to standard males. In this respect, drive males are subject to and exert weak sexual selection.\n\nLay summaryWe studied male mate preference in stalk-eyed flies. This species suffers from meiotic drive, a selfish genetic element that causes a reduction in sperm production and organismal fitness. We predicted that males with meiotic drive would show weak mate preference. Males preferred to mate with large females, but there was no difference in the strength of preference between drive and non-drive males. Males with larger eyespan showed stronger mate preference. Meiotic drive males usually have reduced eyespan so on average they exert weaker sexual selection on females, but this is mediated by eyespan, not genotype per se.

evolutionary biology↗