Biology subjects

Steadman, M.

Publications and source records attributed to Steadman, M..

3 recordsLinked to original sources

bioRxiv2024

Impaired DNA damage response and inflammatory signalling underpins hematopoietic stem cell defects in Gata2 haploinsufficiency

Clinical GATA2 deficiency syndromes arise from germline haploinsufficiency inducing mutations in GATA2, resulting in immunodeficiency that evolves to myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML). How GATA2 haploinsufficiency disrupts the function and transcriptional network of hematopoietic stem/progenitors (HSCs/HSPCs) to facilitate the shift from immunodeficiency to pre-leukemia is poorly characterised. Using a conditional mouse model harboring a single allele deletion of Gata2 from the start of HSC development in utero, we identified pervasive defects in HSPC differentiation from young adult Gata2 haploinsufficient mice during B-cell development, early erythroid specification, megakaryocyte maturation to platelets and inflammatory cell generation. Gata2 haploinsufficiency abolished HSC self-renewal and multi-lineage differentiation capacity. These functional alterations closely associated with deregulated DNA damage responses and inflammatory signalling conveyed from Gata2 haploinsufficient HSCs. We identified genetic interplay between Gata2 and Asxl1, a driver of DNA damage and inflammation and, notably, a recurrent secondary mutation found in GATA2 haploinsufficiency disease progression to MDS/AML. shRNA mediated knockdown of Asxl1 in Gata2 haploinsufficient HSPCs led to an enhanced differentiation block in vitro. By analysis of HSCs from young adult compound Gata2/Asxl1 haploinsufficient mice, we discovered hyperproliferation of double haploinsufficient HSCs, which were also functionally compromised in transplantation compared to their single Gata2 or Asxl1 haploinsufficient counterparts. Through both Gata2/Asxl1 dependent and unique transcriptional programs, HSCs from compound Gata2/Asxl1 haploinsufficient fortified deregulated DNA damage responses and inflammatory signalling initiated in Gata2 haploinsufficient HSCs and established a broad pre-leukemic program. Our data reveal how Gata2 haploinsufficiency initially drives deregulation of HSC genome integrity and suggest the mechanisms of how secondary mutations like ASXL1 take advantage of HSC genomic instability to nurture a pre-leukemic state in GATA2 haploinsufficiency syndromes.

cancer biology↗

bioRxiv2023

13C metabolite tracing reveals glutamine and acetate as critical in vivo fuels for CD8+ T cells

Infusion of 13C-labeled metabolites provides a gold-standard for understanding the metabolic processes used by T cells during immune responses in vivo. Through infusion of 13C-labeled metabolites (glucose, glutamine, acetate) in Listeria monocytogenes (Lm)-infected mice, we demonstrate that CD8+ T effector (Teff) cells utilize metabolites for specific pathways during specific phases of activation. Highly proliferative early Teff cells in vivo shunt glucose primarily towards nucleotide synthesis and leverage glutamine anaplerosis in the tricarboxylic acid (TCA) cycle to support ATP and de novo pyrimidine synthesis. Additionally, early Teff cells rely on glutamic-oxaloacetic transaminase 1 (Got1)--which regulates de novo aspartate synthesis--for effector cell expansion in vivo. Importantly, Teff cells change fuel preference over the course of infection, switching from glutamine-to acetate-dependent TCA cycle metabolism late in infection. This study provides insights into the dynamics of Teff metabolism, illuminating distinct pathways of fuel consumption associated with Teff cell function in vivo. TeaserInterrogating dynamics of fuel utilization by CD8+ T cells in vivo reveals new metabolic checkpoints for immune function in vivo.

immunology↗

bioRxiv2021

Composite receptive fields in the mouse auditory cortex

AO_SCPLOWBSTRACTC_SCPLOWA central question in sensory neuroscience is how neurons represent complex natural stimuli. This process involves multiple steps of feature extraction to obtain a condensed, categorical representation useful for classification and behavior. It has previously been shown that central auditory neurons in the starling have composite receptive fields composed of multiple features when probed with conspecific songs. Whether this property is an idiosyncratic characteristic of songbirds, a group of highly specialized vocal learners, or a generic characteristic of central auditory systems in different animals is, however, unknown. To address this question, we have recorded responses from auditory cortical neurons in mice, and characterized their receptive fields using mouse ultrasonic vocalizations (USVs) as a natural and ethologically relevant stimulus and pitch-shifted starling songs as a natural but ethologically irrelevant control stimulus. We have found that auditory cortical neurons in the mouse display composite receptive fields with multiple excitatory and inhibitory subunits. Moreover, this was the case with either the conspecific or the heterospecific vocalizations. We then trained the sparse filtering algorithm on both classes of natural stimuli to obtain statistically optimal features, and compared the natural and artificial features using UMAP, a dimensionality-reduction algorithm previously used to analyze mouse USVs and birdsongs. We have found that the receptive-field features obtained with the mouse USVs and those obtained with the pitch-shifted starling songs clustered together, as did the sparse-filtering features. However, the natural and artificial receptive-field features clustered mostly separately. These results indicate that composite receptive fields are likely a generic property of central auditory systems in different classes of animals. They further suggest that the quadratic receptive-field features of the mouse auditory cortical neurons are natural-stimulus invariant.

neuroscience↗