Biology subjects

Smith, F. M.

Publications and source records attributed to Smith, F. M..

6 recordsLinked to original sources

bioRxiv2026

Prey diversity revealed by environmental DNA elucidates ecological specialisation and social structure in bottlenose dolphins

Human disturbance drives rapid biodiversity loss, yet how prey diversity shapes individual niche differentiation and scales up to structure social organisation remains poorly understood, particularly in marine systems where prey are largely invisible to observation. Here we mapped prey community structure ( prey fields) using environmental DNA metabarcoding, integrating these maps with stable isotope data and >20 years of behavioural observations on bottlenose dolphins. We show that dolphins specialised on specific prey fields to varying degrees, and that none of 471 tracked individuals changed their predominant prey field -- even through climate-driven habitat reorganisation. Isotope profiles confirmed dietary differentiation scaling with specialisation strength. Across four independent sex-subpopulation networks, prey field overlap predicted social affinity in non-foraging contexts, revealing that prey community structure organises social ties beyond foraging. These results expose a socio-ecological link between prey diversity, trophic ecology, and social organisation, providing a transferable eDNA framework for predators with elusive prey.

ecology↗

bioRxiv2025

Mitochondrial metabolism is rapidly re-activated in mature neutrophils to support stimulation-induced response

Neutrophils are highly abundant innate immune cells that are constantly produced from myeloid progenitors in the bone marrow. Differentiated neutrophils can perform an arsenal of effector functions critical for host defense. This study aims to quantitatively understand neutrophil mitochondrial metabolism throughout differentiation and activation, and to elucidate the impact of mitochondrial metabolism on neutrophil functions. To study metabolic remodeling throughout neutrophil differentiation, murine ER-Hoxb8 myeloid progenitor-derived neutrophils and human induced pluripotent stem cell-derived neutrophils were assessed as models. To study the metabolic remodeling upon neutrophil activation, differentiated ER-Hoxb8 neutrophils and primary human neutrophils were activated with various stimuli, including ionomycin, MSU crystals, and PMA. Characterization of cellular metabolism by isotopic tracing, extracellular flux analysis, metabolomics, and fluorescence-lifetime imaging microscopy revealed dynamic changes in mitochondrial metabolism. As neutrophils mature, mitochondrial metabolism decreases drastically, energy production is fully offloaded from oxidative phosphorylation, and glucose oxidation through TCA cycle is substantially reduced. Nonetheless, mature neutrophils retain the capacity for mitochondrial metabolism. Upon stimulation with certain stimuli, TCA cycle is rapidly activated. Mitochondrial pyruvate carrier inhibitors reduce this re-activation of the TCA cycle and inhibit the release of neutrophil extracellular traps. Mitochondrial metabolism also impacts neutrophil redox status, migration, and apoptosis without significantly changing overall bioenergetics. Together, these results demonstrate that mitochondrial metabolism is dynamically remodeled and plays a significant role in neutrophil function and fate. Furthermore, these findings point to the therapeutic potential of mitochondrial pyruvate carrier inhibitors in a range of conditions where dysregulated neutrophil response drives inflammation and contributes to pathology.

immunology↗

bioRxiv2024

GATA1-deficient human pluripotent stem cells generate neutrophils with improved antifungal immunity that is mediated by the integrin CD18

Neutrophils are critical for host defense against fungi. However, the short life span and lack of genetic tractability of primary human neutrophils has limited in vitro analysis of neutrophil-fungal interactions. Human induced pluripotent stem cell (iPSC)-derived neutrophils (iNeutrophils) are a genetically tractable alternative to primary human neutrophils. Here, we show that deletion of the transcription factor GATA1 from human iPSCs results in iNeutrophils with improved antifungal activity against Aspergillus fumigatus. GATA1 knockout (KO) iNeutrophils have increased maturation, antifungal pattern recognition receptor expression and more readily execute neutrophil effector functions compared to wild-type iNeutrophils. iNeutrophils also show a shift in their metabolism following stimulation with fungal {beta}-glucan, including an upregulation of the pentose phosphate pathway (PPP), similar to primary human neutrophils in vitro. Furthermore, we show that deletion of the integrin CD18 attenuates the ability of GATA1-KO iNeutrophils to kill A. fumigatus but is not necessary for the upregulation of PPP. Collectively, these findings support iNeutrophils as a robust system to study human neutrophil antifungal immunity and has identified specific roles for CD18 in the defense response. Author SummaryNeutrophils are important first responders to fungal infections, and understanding their antifungal functions is essential to better elucidating disease dynamics. Primary human neutrophils are short lived and do not permit genetic manipulation, limiting their use to study neutrophil-fungal interactions in vitro. Human induced pluripotent stem cell (iPSC)-derived neutrophils (iNeutrophils) are a genetically tractable alternative to primary human neutrophils for in vitro analyses. In this report we show that GATA1-deficient iPSCs generate neutrophils (iNeutrophils) that are more mature than wild-type iNeutrophils and display increased antifungal activity against the human fungal pathogen Aspergillus fumigatus. We also show that GATA1-deficient iNeutrophils have increased expression of antifungal receptors than wild-type cells and shift their metabolism and execute neutrophil antifungal functions at levels comparable to primary human neutrophils. Deletion of the integrin CD18 blocks the ability of GATA1-deficient iNeutrophils to kill and control the growth of A. fumigatus, demonstrating an important role for this integrin in iNeutrophil antifungal activity. Collectively, these findings support the use of iNeutrophils as a model to study neutrophil antifungal immunity.

microbiology↗

bioRxiv2024

Grb7, Grb10 and Grb14, encoding the growth factor receptor-bound 7 family of signalling adaptor proteins have overlapping functions in the regulation of fetal growth and post-natal glucose metabolism

BackgroundThe growth factor receptor bound 7 (Grb7) family of signalling adaptor proteins comprises Grb7, Grb10 and Grb14. Each can interact with the insulin receptor and other receptor tyrosine kinases, where Grb10 and Grb14 inhibit insulin receptor activity. In cell culture studies they mediate functions including cell survival, proliferation, and migration. Mouse knockout (KO) studies have revealed physiological roles for Grb10 and Grb14 in glucose-regulated energy homeostasis. Both Grb10 KO and Grb14 KO mice exhibit increased insulin signalling in peripheral tissues, with increased glucose and insulin sensitivity and a modestly increased ability to clear a glucose load. In addition, Grb10 strongly inhibits fetal growth such that at birth Grb10 KO mice are 30% larger by weight than wild type littermates. ResultsHere, we generate a Grb7 KO mouse model. We show that during fetal development the expression patterns of Grb7 and Grb14 each overlap with that of Grb10. Despite this, Grb7 and Grb14 did not have a major role in influencing fetal growth, either alone or in combination with Grb10. At birth, in most respects both Grb7 KO and Grb14 KO single mutants were indistinguishable from wild type, while Grb7:Grb10 double knockout (DKO) were near identical to Grb10 KO single mutant and Grb10:Grb14 DKO mutants slightly smaller. In the developing kidney Grb7 had a subtle positive influence on growth. An initial characterisation of Grb7 KO adult mice revealed sexually dimorphic effects on energy homeostasis, with females having significantly smaller white adipose tissue (WAT) depots and an enhanced ability to clear glucose from the circulation, compared to wild type littermates. Males had elevated fasted glucose levels with a trend towards smaller WAT depots, without improved glucose clearance. ConclusionsGrb7 and Grb14 do not have significant roles as inhibitors of fetal growth, unlike Grb10, and instead Grb7 may promote growth of the developing kidney. In adulthood, Grb7 contributes subtly to glucose mediated energy homeostasis, raising the possibility of redundancy between all three adaptors in physiological regulation of insulin signalling and glucose handling.

developmental biology↗

bioRxiv2024

Imprinted Grb10, encoding growth factor receptor bound protein 10, regulates fetal growth independently of the insulin-like growth factor type 1 receptor (Igf1r) and insulin receptor (Insr) genes

BackgroundOptimal size at birth dictates perinatal survival and long-term risk of developing common disorders such as obesity, type 2 diabetes and cardiovascular disease. The imprinted Grb10 gene encodes a signalling adaptor protein capable of inhibiting receptor tyrosine kinases, including the insulin receptor (Insr) and insulin-like growth factor type 1 receptor (Igf1r). Grb10 restricts fetal growth such that Grb10 knockout (KO) mice are at birth some 25-35% larger than wild type. Using a mouse genetic approach, we test the widely held assumption that Grb10 influences growth through interaction with Igf1r, which has a highly conserved growth promoting role. ResultsShould Grb10 interact with Igf1r to regulate growth Grb10:Igf1r double mutant mice should be indistinguishable from Igf1r KO single mutants, which are around half normal size at birth. Instead, Grb10:Igf1r double mutants were intermediate in size between Grb10 KO and Igf1r KO single mutants, indicating additive effects of the two signalling proteins having opposite actions in separate pathways. Some organs examined followed a similar pattern, though Grb10 KO neonates exhibited sparing of the brain and kidneys, whereas the influence of Igf1r extended to all organs. An interaction between Grb10 and Insr was similarly investigated. While there was no general evidence for a major interaction for fetal growth regulation, the liver was an exception. The liver in Grb10 KO mutants was disproportionately overgrown with evidence of excess lipid storage in hepatocytes, whereas Grb10:Insr double mutants were indistinguishable from Insr single mutants or wild types. ConclusionsGrb10 acts largely independently of Igf1r or Insr to control fetal growth and has a more variable influence on individual organs. Only the disproportionate overgrowth and excess lipid storage seen in the Grb10 KO neonatal liver can be explained through an interaction between Grb10 and the Insr. Our findings are important for understanding how positive and negative influences on fetal growth dictate size and tissue proportions at birth.

developmental biology↗

bioRxiv2023

Frataxin-deficient human brain microvascular endothelial cells lose polymerized actin and are paracellularly permeable -implications for blood-brain barrier integrity in Friedreich's Ataxia

BackgroundFriedreichs Ataxia (FRDA) is the most prevalent inherited ataxia; the disease results from loss of Frataxin, an essential mitochondrial iron trafficking protein. FRDA presents as neurodegeneration of the dorsal root ganglion and cerebellar dentate nuclei, followed by brain iron accumulation in the latter. End stage disease includes cardiac fibrosis that contributes to hypertrophic cardiomyopathy. The microvasculature plays an essential barrier role in both the brain and heart, thus an investigation of this tissue system in FRDA is essential to the delineation of the cellular dysfunction in this genetic disorder. Here, we investigate brain microvascular endothelial cell integrity in FRDA in a model of the blood-brain barrier (BBB). MethodsWe used lentiviral mediated shRNA delivery to generate a novel FRDA model in immortalized human brain microvascular endothelial cells (hBMVEC) that compose the microcapillaries of the BBB. We verified known cellular pathophysiologies of FXN knockdown including increased oxidative stress, loss of energy metabolism, and increased cell size. Furthermore, we investigated cytoskeletal architecture including the abundance and organization of filamentous actin, and barrier physiology via transendothelial electrical resistance and fluorescent tracer flux. ResultsshFXN hBMVEC display the known FRDA cell morbidity including increased oxidative stress, decreased energy metabolism, and an increase in cell size. We demonstrate that shFXN hBMVEC have less overall filamentous actin, and that filamentous actin is lost at the cell membrane and cortical actin ring. Consistent with loss of cytoskeletal structure and anchorage, we found decreased barrier strength and increased paracellular tracer flux in the shFXN hBMVEC transwell model. ConclusionWe identified that insufficient FXN levels in the hBMVEC BBB model causes changes in cytoskeletal architecture and increased barrier permeability, cell pathologies that may be related to patient brain iron accumulation, neuroinflammation, neurodegeneration, and stroke. Our findings implicate other barrier cells, e.g., the cardiac microvasculature, likely contributory also to disease pathology in FRDA.

biochemistry↗