Biology subjects

McLeod, J.

Publications and source records attributed to McLeod, J..

8 recordsLinked to original sources

bioRxiv2026

Locus-specific transposable element expression drives human hematopoietic stem cell disease pathophysiology

VEXAS syndrome (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) is a severe, inflammatory syndrome resulting from mutated UBA1 leading to hematopoietic stem cells (HSC) expansion. Although UBA1-mutant HSC show complex phenotypes including proteostasis defects, sustained inflammation and clonal expansion of myeloid biased progeny, the pathogenic mechanisms at the HSC level are unknown from these gene-centric studies alone. By focussing on the non-coding genome and using advanced functional genetic methods, we found that VEXAS HSC, compared to controls, had altered expression of individual transposable elements (TE) and are key regulators of VEXAS pathogenesis. Locus-specific TE quantification identified two L1 elements, L1-10 and L1-15, active in both normal and VEXAS HSC that drive myeloid commitment by co-opting SPI1 and IRF1 transcription factors (TF) via networks common to other myeloid-biased conditions. Lipid nanoparticle (LNP)-mediated CRISPRi of L1-10 and L1-15 in UBA1-mutant HSC also caused reversion of VEXAS-associated functional phenotypes in vitro and in vivo. Functionally, pharmacologic inhibition of UBA1 with TAK-243 led to L1-10 and L1-15 RNA accumulation, while enhancement of UBA1 activity with Auranofin reversed this effect. Our study provides direct evidence that VEXAS-specific TE govern HSC clonal dominance, thereby uncovering a regulatory axis underlying HSC biology and disease mechanisms, opening a therapeutic strategy directed towards the repetitive genome.

genetics↗

bioRxiv2024

Hematopoietic Tet2 inactivation enhances the response to checkpoint blockade immunotherapy

Somatic mutations inactivating TET2 are among the most common drivers of clonal hematopoiesis (CH). While TET2 inactivation is associated with monocyte-derived inflammation and improved chimeric antigen-receptor-T cell function, its impact on immunotherapy response is unknown. In our mouse model, hematopoietic Tet2 mutation enhanced immune checkpoint blockade (ICB) response. Enhanced ICB response with Tet2 mutation required phagocytes, CD4 and CD8 T cells. Mechanistically, in Tet2-mutant tumor-infiltrating leukocytes (TILs), ICB preferentially induced anti-tumor states and restricted cell states linked to tumor progression. Tet2-mutant monocytes activated costimulatory programs, while Tet2-mutant T cells showed enhanced T cell memory signatures, lesser exhaustion and decreased regulatory phenotype. Our murine data was clinically relevant, since we found that melanomas from patients with TET2 driver mutation-CH (TET2-CH) showed enhanced immune infiltration, T cell activation, and T cell memory programs. In melanoma patients treated with ICB, TET2-CH was associated with 6-fold greater odds of clinical benefit. Collectively, our data establishes that hematopoietic Tet2 inactivation primes leukocytes for anti-tumor states associated with immunotherapy response and provides a potential biomarker for personalized therapy.

cancer biology↗

bioRxiv2024

Towards a Taxonomy Machine. A Training Set of 5.6 Million Arthropod Images

The taxonomic identification of organisms from images is an active research area within the machine learning community. Current algorithms are very effective for object recognition and discrimination, but they require extensive training datasets to generate reliable assignments. This study releases 5.6 million images with representatives from 10 arthropod classes and 26 insect orders. All images were taken using a Keyence VHX-7000 Digital Microscope system with an automatic stage to permit high-resolution (4K) microphotography. Providing phenotypic data for 324,000 species derived from 48 countries, this release represents, by far, the largest dataset of standardized arthropod images. As such, this dataset is well suited for testing the efficacy of machine learning algorithms for identifying specimens to higher taxonomic categories.

bioinformatics↗

bioRxiv2024

FLT3 is genetically essential for ITD-mutated leukemic stem cells but dispensable for human hematopoietic stem cells

Leukemic stem cells (LSCs) fuel acute myeloid leukemia (AML) growth and relapse, but therapies tailored towards eradicating LSCs without harming healthy hematopoietic stem cells (HSCs) are lacking. FLT3 is considered an important therapeutic target due to frequent mutation in AML and association with relapse. However, there has been limited clinical success with FLT3 targeting, suggesting either that FLT3 is not a vulnerability in LSC, or that more potent inhibition is required, a scenario where HSC toxicity could become limiting. We tested these possibilities by ablating FLT3 using CRISPR/Cas9-mediated FLT3 knock-out (FLT3-KO) in human LSCs and HSCs followed by functional xenograft assays. FLT3-KO in LSCs from FLT3-ITD mutated, but not FLT3-WT AMLs, resulted in short-term leukemic grafts of FLT-3-KO edited cells that disappeared by 12 weeks. By contrast, FLT3-KO in HSCs from fetal liver, cord blood and adult bone marrow did not impair multilineage hematopoiesis in primary and secondary xenografts. Our study establishes FLT3 as an ideal therapeutic target where ITD+ LSC are eradicated upon FLT3 deletion, while HSCs are spared. These findings support the development of more potent FLT3-targeting drugs or gene-editing approaches for LSC eradication to improve clinical outcomes. KEY POINTSThe FLT3 gene is essential for ITD-mutated leukemic stem cells (LSCs) to establish and propagate leukemia. Normal human hematopoietic stem cells (HSCs) do not require FLT3 to engraft and sustain hematopoiesis. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=179 SRC="FIGDIR/small/601363v1_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@b77f56org.highwire.dtl.DTLVardef@109011dorg.highwire.dtl.DTLVardef@282e04org.highwire.dtl.DTLVardef@1e51e3b_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2023

Distinct effects of priming the brain using tDCS and observational practice: new evidence from brain effective connectivity.

Complex motor skills can be acquired while observing a model without physical practice. Transcranial direct-current stimulation (tDCS) applied to the primary motor cortex (M1) also facilitates motor learning. However, the effectiveness of observational practice for bimanual coordination skills is debated and there is little research on the effects of tDCS on acquiring bimanual skills and the underlying effective/causal brain connectivity. We compared the effect of primary motor cortex tDCS (M1-tDCS) to action-observation (AO) when acquiring a bimanual, two-ball juggling skill and characterized the brain causal connectivity patterns underlying each condition. Twenty healthy young adults with no juggling experience were randomly assigned to either video observation of a skilled juggler or anodal M1-tDCS. Thirty trials of juggling were performed and scored after the intervention. Resting-state EEG data were collected before and after the intervention. Information flow rate was applied to EEG source data to measure causal connectivity. Juggling scores were significantly higher in the AO group (p =.03). We found the strongest information exchange from (L) parietal to (R) parietal regions, strong bidirectional information exchange between (R) parietal and (R) occipital regions and an extensive network of activity that was (L) lateralized in the AO condition. In contrast, the M1-tDCS condition was characterized by bilateral long-range connections with the strongest information exchange from the (R) occipital region to the (R) temporal and (L) occipital regions. This study provides new results about the distinct network dynamics of priming the brain for skill acquisition using direct stimulation or indirect stimulation via action observation.

neuroscience↗

bioRxiv2023

A hematopoietic stem cell subset that retains memory of prior inflammatory stress accumulates in aging and clonal hematopoiesis

Inflammation activates many blood cell types, driving aging and malignancy. Yet, hematopoietic stem cells (HSCs) survive a lifetime of infection to sustain life-long blood production. To understand HSC adaptation to inflammation, we developed xenograft inflammation-recovery models and performed single cell multiomics on isolated human HSC. Two transcriptionally and epigenetically distinct HSC subsets expressing canonical HSC programs were identified. Only one showed sustained transcriptional and epigenetic changes after recovery from inflammatory treatments. This HSC inflammatory memory (HSC-iM) program is enriched in memory T cells and HSCs from recovered COVID-19 patients. Importantly, HSC-iM accumulates with age and with clonal hematopoiesis. Overall, heritable molecular alterations in a subset of human HSCs, an adaptation to long-term inflammatory stress, may predispose to heightened age-related risk of blood cancer and infection. One-Sentence SummaryInflammation across a lifetime rewires human HSCs to produce a distinct HSC subset with both beneficial and deleterious fitness consequences.

cell biology↗

bioRxiv2022

Adaptation to ex vivo culture drives human haematopoietic stem cell loss of repopulation capacity in a cell cycle independent manner

Loss of long-term haematopoietic stem cell function (LT-HSC) hampers the success of ex vivo HSC gene therapy and expansion procedures, but the kinetics and the mechanisms by which this occurs remain incompletely characterized. Here through time-resolved scRNA-Seq, matched in vivo functional analysis and the use of a reversible in vitro system of early G1 arrest, we define the sequence of transcriptional and functional events occurring during the first ex vivo division of human LT-HSCs. We demonstrate that contrary to current assumptions, loss of long-term repopulation capacity during culture is independent of cell cycle progression. Instead it is a rapid event that follows an early period of adaptation to culture, characterised by transient gene expression dynamics and constrained global variability in gene expression. Cell cycle progression however contributes to the establishment of differentiation programmes in culture. Our data have important implications for improving HSC gene therapy and expansion protocols.

cell biology↗

bioRxiv2021

Effects of High-Volume versus High-Load Resistance Training on Skeletal Muscle Growth and Molecular Adaptations

AimWe evaluated the effects of higher-load (HL) versus (lower-load) higher-volume (HV) resistance training on skeletal muscle hypertrophy, strength, and muscle-level molecular markers. MethodsTrained men (n=15, age: 23{+/-}3 y; training experience: 7{+/-}3 y) performed unilateral lower body training for 6 weeks (3x weekly), where single legs were assigned to HV and HL paradigms. Vastus lateralis (VL) biopsies were obtained prior to study initiation (PRE) as well as 3 days (POST) and 10 days following the last bout (POSTPR). Body composition and strength tests were performed at each testing session, and biochemical assays were performed on muscle tissue after study completion. Two-way within subjects repeated measures ANOVAs were performed on all dependent variables except tracer data, which was compared using dependent samples t-tests. ResultsA significant (p<0.05) interaction existed for unilateral leg extension 1RM (HV<HL at POST and POSTPR). Six-week integrated sarcoplasmic protein synthesis (iSarcoPS) rates were higher in the HV versus HL leg, while no difference between legs existed for integrated myofibrillar protein synthesis rates. Main time effects existed for unilateral leg press strength (PRE<POST and POSTPR), knee extensor peak torque (PRE and POST<POSTPR), dual-energy x-ray absorptiometry (DXA)-derived upper leg lean mass (PRE<POST and POSTPR), ultrasound-derived VL thickness (PRE and POSTPR<POST), sarcoplasmic protein concentrations (POST and POSTPR<PRE), and tropomyosin and troponin protein abundances (POST and POSTPR<PRE). ConclusionsWith the exception of differences in leg extensor strength and iSarcoPS between legs, our data suggest that short-term (6 weeks) HV and HL training elicit similar hypertrophic, strength, and molecular-level adaptations.

physiology↗