Biology subjects

Francis, C.

Publications and source records attributed to Francis, C..

6 recordsLinked to original sources

bioRxiv2026

The Nuclear-Cytoskeletal Interface Is a Vulnerability in Aging Endothelium

Vascular aging is a fundamental driver of age-related cardiovascular diseases. Endothelial cells (ECs) lining the vascular lumen of capillaries are specialized, thin cells that supply tissues with metabolites, and their loss in aging poses a threat to tissue perfusion and ischemia risk. Mechanisms causing capillary dropout in aging are largely unknown, although VEGF signaling deficiency is implicated.15 To identify mechanisms involved in vascular aging, we investigated mice with the accelerated aging disorder Progeria, and aged wildtype mice. At the organismal level, Progerin expression reduced sprouting angiogenesis and capillary density in neonatal mouse retinas, which impaired tissue perfusion and increased DNA damage compared to wildtype littermates. Progeric capillaries and aortic ECs displayed a disrupted nuclear-cytoskeletal interface that was shared with aged wildtype mice. 4D EC sprouts derived from Progeria mice had mispositioned nuclei at sprouting tips and bulging nuclei that failed to flatten and obstructed lumen formation, demonstrating cell autonomous defects. Progerin expression in human ECs likewise affected nuclear positioning and flattening and prevented sprouting and lumen formation. Mechanistically, Progerin expression altered LINC complex protein abundance resulting in a failed connection with cytoskeletal Actin and the intermediate filament protein Vimentin. Impairment of the nuclear-cytoskeletal interface was conserved in Progeria patient derived ECs, and partially rescued by inhibiting Progerin with the drug, Progerinin. Taken together, our results reveal that nuclear positioning and flattening is required for angiogenic sprouting and lumen formation respectively and identify the nuclear-cytoskeletal interface as a vulnerability for age-related microvascular dropout and a target for therapeutic intervention.

cell biology↗

bioRxiv2025

Crystal Structure of 3-Hydroxypropionyl-CoA Synthetase (ADP-forming) from Nitrosopumilus maritimus

The 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) cycle in thaumarchaeota contributes significantly to global organic carbon fixation as the most energetically efficient aerobic carbon fixation pathway. The thaumarchaeal 3-Hydroxypropionyl-CoA Synthetase (ADP-forming; Nmar_1309) is crucial to this efficiency, utilizing ATP to ADP catalysis. This first reported structure of Nmar_1309 reveals a homodimer with a unique subdomain organization ([3-4-1-2-5]) and a distinct linker between subdomains 4 and 1. The presence of bound substrates including 3-hydroxypropionate, non-hydrolyzable ATP (ADPNP), and a phosphate suggests an intermediate state mimicking a reaction step immediately preceding the formation of a 3-hydroxypropionyl-phosphohistidine. Conformational differences were observed between the two chains of the homodimer, likely influenced by the binding of a single ADPNP molecule in one chain. Phylogenetic analysis suggests that while 4HB synthetases may have evolved earlier in the evolutionary timeline, 3HP synthetases in Thaumarchaeota may have occurred after the Great Oxygenation Event. These structural data provide further characterization of the 3HP/4HB cycle and, in conjunction with the structure of 4-hydroxybutyryl-CoA synthetase, Nmar_0206, provide baseline structures of the key ADP-forming Acyl-CoA synthetases within this pathway.

biophysics↗

bioRxiv2024

Endothelial Rho kinase controls blood vessel integrity and angiogenesis

BackgroundThe Rho kinases 1 and 2 (ROCK1/2) are serine-threonine specific protein kinases that control actin cytoskeleton dynamics. They are expressed in all cells throughout the body, including cardiomyocytes, smooth muscle cells and endothelial cells, and intimately involved in cardiovascular health and disease. Pharmacological ROCK inhibition is beneficial in mouse models of hypertension, atherosclerosis, and neointimal thickening that display overactivated ROCK. However, the consequences of endothelial ROCK signaling deficiency in vivo remain unknown. To address this issue, we analyzed endothelial cell (EC) specific ROCK1 and 2 deletions. MethodsWe generated Cdh5-CreERT2 driven, tamoxifen inducible loss of function alleles of ROCK1 and ROCK2 and analyzed mouse survival and vascular defects through cellular, biochemical, and molecular biology approaches. ResultsWe observed that postnatal or adult loss of endothelial ROCK1 and 2 was lethal within a week. Mice succumbed to multi-organ hemorrhage that occurred because of loss of vascular integrity. ECs displayed deficient cytoskeletal actin polymerization that prevented focal adhesion formation and disrupted junctional integrity. Retinal sprouting angiogenesis was also perturbed, as sprouting vessels exhibited lack of polymerized actin and defective lumen formation. In a three-dimensional endothelial sprouting assay, combined knockdown of ROCK1/2 or knockdown or ROCK2 but not ROCK1 led to reduced sprouting, lumenization and cell polarization defects caused by defective actin and altered VE-cadherin dynamics. The isoform specific role of endothelial ROCK2 correlated with ROCK2 substrate specificity for FAK and LIMK. By analyzing single and three allele mutants we show that one intact allele of ROCK2 is sufficient to maintain vascular integrity in vivo. ConclusionEndothelial ROCK1 and 2 maintain junctional integrity and ensure proper angiogenesis and lumen formation. The presence of one allele of ROCK2 is sufficient to maintain vascular growth and integrity. These data indicate the need of careful consideration for the use of ROCK inhibitors in disease settings.

developmental biology↗

bioRxiv2022

Out of thin air: surveying tropical bat roosts through air sampling of eDNA

Understanding roosting behaviour is essential to bat conservation and biomonitoring, often providing the most accurate methods of assessing population size and health. However, roosts can be challenging to survey. Roosts can be physically impossible to access or present risks for researchers and disturbance during monitoring can disrupt natural bat behaviour and present material risks to the population e.g. disrupting hibernation cycles. One solution to this is the use of non-invasive monitoring approaches. Environmental (e)DNA has proven especially effective at detecting rare and elusive species particularly in hard-to-reach locations. It has recently been demonstrated that eDNA is carried in air and, when collected in semi-confined spaces can provide remarkably accurate profiles of biodiversity, even in complex tropical communities. In this study we deploy novel airborne eDNA collection for air for the first time in a natural setting and use this approach to survey difficult to access potential roosts in the neotropics. Using airborne eDNA we confirmed the presence of bats in 9 out of 12 roosts. The identified species matched previous historical records of roost use obtained from photographic and live capture methods demonstrating the utility of this approach. We also detected the presence of the white-winged vampire bat (Diaemus youngi) which had never been confirmed in the area but was long suspected. In addition to the bats, we also detected several non-bat vertebrates, including the big-eared climbing rat (Ototylomys phyllotis), which has previously been observed in and around bat roosts. We also detected eDNA from other local species known to be in the vicinity. Using airborne eDNA to detect new roosts and monitor known populations, particularly when species turnover is rapid, could maximize efficiency for surveyors while minimizing disturbance to the animals. This study presents the first applied use of airborne eDNA collection for ecological analysis and demonstrates a clear utility for this technology in the wild.

ecology↗

bioRxiv2020

A plasma membrane nanoplatform ensures signal specificity during osmotic signaling in plants

In the course of their growth and development plants have to constantly perceive and react to their environment. This is achieved in cells, by the coordination of complex combinatorial signaling networks. However, how signal integration and specificity are achieved in this context is unknown. With a focus on the hyperosmotic stimulus, we use live super-resolution light imaging methods to demonstrate that a Rho GTPase, Rho-of-Plant 6 (ROP6), forms stimuli-dependant nanodomains within the PM. These nanodomains are necessary and sufficient to transduce production of reactive oxygen species (ROS),that act as secondary messengers and trigger several plant adaptive responses to osmotic constraints. Furthermore, ROP6 activation triggers the nanoclustering of two NADPH oxidases that subsequently generates ROS. ROP6 nanoclustering is also needed for cell surface auxin signaling, but short-time auxin treatment does not induce ROS accumulation. We show that auxin-induced ROP6 nanodomains, unlike osmotically-driven ROP6 clusters, do not recruit the NADPH oxidase, RBOHD. Together, our results suggest that Rho GTPase nano-partitioning at the PM ensure signal specificity downstream of independent stimuli.

plant biology↗

bioRxiv2017

CardioClassifier: demonstrating the power of disease- and gene-specific computational decision support for clinical genome interpretation

PurposeInternationally-adopted variant interpretation guidelines from the American College of Medical Genetics and Genomics (ACMG) are generic and require disease-specific refinement. Here we developed CardioClassifier (www.cardioclassifier.org), a semi-automated decision-support tool for inherited cardiac conditions (ICCs).\n\nMethodsCardioClassifier integrates data retrieved from multiple sources with user-input case-specific information, through an interactive interface, to support variant interpretation. Combining disease- and gene-specific knowledge with variant observations in large cohorts of cases and controls, we refined 14 computational ACMG criteria and created three ICC-specific rules.\n\nResultsWe benchmarked CardioClassifier on 57 expertly-curated variants and show full retrieval of all computational data, concordantly activating 87.3% of rules. A generic annotation tool identified fewer than half as many clinically-actionable variants (64/219 vs 156/219, Fishers P=1.1x10-18), with important false positives; illustrating the critical importance of disease and gene-specific annotations.\n\nCardioClassifier identified putatively disease-causing variants in 33.7% of 327 cardiomyopathy cases, comparable with leading ICC laboratories. Through addition of manually-curated data, variants found in over 40% of cardiomyopathy cases are fully annotated, without requiring additional user-input data.\n\nConclusionCardioClassifier is an ICC-specific decision-support tool that integrates expertly curated computational annotations with case-specific data to generate fast, reproducible and interactive variant pathogenicity reports, according to best practice guidelines.

genomics↗