Biology subjects

Moret, A.

Publications and source records attributed to Moret, A..

4 recordsLinked to original sources

bioRxiv2025

An expanded palette of bright and photostable organellar Ca2+ sensors

The use of fluorescent sensors for functional imaging has revolutionized the study of organellar Ca2+ signaling. However, understanding the dynamic interplay between intracellular Ca2+ sinks and sources has been hindered by the lack of bright, photostable, and multiplexed measurements in different organelles, limiting our ability to define how Ca2+ shapes cell physiology across fields of biology. Here we introduce a new toolkit of chemigenetic organellar Ca2+ indicators whose color is tunable by reconstituting their fluorescence with different exogenous rhodamine dye-ligands, which significantly expand the capacity for multiplexing organellar Ca2+ measurements. These sensors, which we named ER-HaloCaMP and Mito-HaloCaMP, are optimized to report Ca2+ dynamics in the endoplasmic reticulum (ER) and mitochondria of mammalian cells and neurons, and show significantly improved brightness, photostability and responsiveness when compared to current best-in-class alternatives. Using either red or far-red dye-ligands, both ER-HaloCaMP and Mito-HaloCaMP enable visualizing ER and mitochondrial Ca2+ dynamics in neuronal axons, a subcellular location that only contains a few ER tubules and small mitochondria, structural limitations that have impaired measurements with previous red sensors. To show the expanded multiplexing capacities of our toolkit, we measured interorganellar Ca2+ fluxes simultaneously in three different subcellular compartments in live cells, revealing that the amplitude of ER Ca2+ release controls the efficacy of ER-mitochondria Ca2+ coupling in a cooperative manner. Organellar HaloCaMPs enable also measuring Ca2+ dynamics in intact brain tissue from flies and rodents, demonstrating their versatility across biological models. Our new toolkit provides an expanded palette of bright, photostable and responsive organellar Ca2+ sensors, which will facilitate future studies of intracellular Ca2+ signaling across fields of biology in health and disease.

cell biology↗

bioRxiv2024

Oxygen deprivation implicated in rapid coral mortality -- an emerging perilous threat to coral reefs

Tropical coral reefs are undergoing unprecedented degradation1, primarily due to the increasing intensity and frequency of marine heatwaves with climate change2-4. Coral bleaching is a well-known ramification of marine heatwaves, but rapid coral mortality is an emerging paradigm that visually manifests as the sloughing of tissue from the coral skeleton. Unlike coral bleaching, coral tissue sloughing precludes any prospect of holobiont recovery beyond the initial onset1,5,6, indicating a life-or-death tipping point. Here, we experimentally confirm this phenomenon occurs when temperatures increase within temporal windows of hours to days, consistent with field observations7,8. Through microscale measurements of dissolved oxygen in the diffusive boundary layers of two abundant, keystone reef-building corals, we demonstrate that rapid temperature increases coincide with intrinsic oxygen deprivation, occurring before gross tissue disintegration or coral tissue sloughing. We propose that this distinct phenomenon arises from rapid heating, rendering the coral holobiont incapable of engaging in reactive processes to counteract the combined effects of heightened aerobic demands and impaired photosynthetic function. The passive diffusion of O2 from the surrounding bulk water is likely insufficient to meet the holobionts requirements, as explained by the Einstein-Smoluchowski kinetic theory of gases and Brownian motion9,10. These insights into coral tissue sloughing underscore the complexity of holobiont responses to stress and biophysical consequences of heatwaves. A granular understanding of these mechanisms is urgently needed, particularly regarding how heating rates may change under future climate scenarios, to re-evaluate the potentially under-recognised threats facing coral reefs.

ecology↗

bioRxiv2024

Hotwiring integrin endocytosis acutely modulates cell interactions

Integrins are heterodimeric cell surface receptors that govern cell-cell interactions, which in turn can influence multiscale processes: cell migration, extracellular matrix remodeling and tissue formation. These processes occur over timescales which range from milliseconds to days. While various strategies exist to study integrin function across biological scales from cell to tissue, they are often chronic and fail to target specific cell-cell interactions acutely. We engineered cells to rapidly alter cell behavior by downregulating the surface population of 5{beta}1 integrins through hot-wired clathrin-mediated endocytosis. This method allows for inducible, specific internalization of 5{beta}1 integrins, achieving acute downregulation across various cell lines in 5-30 minutes. We show that induced internalization of 5{beta}1 decreases the cell area, causes uptake of extracellular fibronectin, and decreases the rate of tumor spheroid compaction. This targeted control of multiscale processes by rapid downregulation of this important class of cell surface receptors demonstrates that hot-wired endocytosis is a useful tool to acutely modulate cell biology.

bioengineering↗

bioRxiv2022

Nitrogen competition is the general mechanism underlying cnidarian-Symbiodiniaceae symbioses

Symbiotic associations with Symbiodiniaceae have evolved independently across a diverse range of cnidarian taxa including reef-building corals, anemones and jellyfish, yet the molecular mechanisms underlying their regulation and repeated evolution are still elusive. Here we show that despite their independent evolution, cnidarian hosts employ the same mechanism of symbiont control in which symbiont-derived glucose is used to assimilate nitrogenous waste via amino acid biosynthesis to limit the availability of nitrogen to the symbionts. In this metabolic interaction, glucose significantly reduces symbiont density while ammonium promotes symbiont proliferation. We show that glucose-derived 13C and ammonium-derived 15N are co-incorporated into amino acids by the hosts. Metabolic differences between the hosts further suggest that corals are more susceptible to environmental stress and symbiosis breakdown due to their increased energy demands to satisfy calcification. Our results reveal the general metabolic interaction underlying these symbioses and provide a parsimonious explanation for their repeated evolution.

ecology↗