Biology subjects

Rodgers, M. L.

Publications and source records attributed to Rodgers, M. L..

5 recordsLinked to original sources

bioRxiv2026

Single-Molecule Dwell Times in Biomolecular Condensates

Biomolecular condensates are dynamic, membrane-free compartments that continuously exchange molecules with their surroundings. The dwell time, defined as the time a molecule remains inside a condensate between entry and exit, determines how extensively the molecule can explore the dense phase and encounter potential binding partners or reaction sites, thereby modulating condensate function. Motivated by our single-molecule measurements of RNA dwell times, we developed an analytical theory to understand dwell-time distributions in biomolecular condensates. Our theory predicts that the dwell-time distributions generally exhibit an early-time power-law regime followed by a late-time exponential tail. The form of the distribution encodes the rate-limiting mechanism of molecular escape: dense-phase diffusion-limited transport feature a -1.5 power law with an exponential tail set by a diffusion timescale, whereas interfacial barrier-crossing-limited transport feature a - 0.5 power law with a decay governed by a barrier-crossing timescale. These distinct signatures provide a direct readout of the physical processes that control molecular retention in condensates, with implications for both natural and synthetic condensates.

biophysics↗

bioRxiv2025

Temperature modulates PFAS accumulation and energy allocation in sheepshead minnows

Climate warming and chemical pollution shape aquatic ecosystems, yet the physiological mechanisms underlying their combined effects remain unclear. We investigated how projected increases in mean summer surface water temperature alter per- and polyfluoroalkyl substances (PFAS) toxicokinetics and their effects on sheepshead minnows (Cyprinodon variegatus) physiological performance. Adult fish were chronically exposed to an environmentally relevant PFAS mixture (perfluorooctane sulfonate (PFOS) + perfluorooctanoate (PFOA)) under current and projected mean-temperature scenarios. Tissue PFAS concentrations, whole-organism metabolic rates, swimming performance, reproductive parameters, somatic indices were assessed. Temperature modified PFAS tissue concentrations in a compound- and tissue-specific manner, promoting PFOA redistribution to eggs. Metabolic responses were temperature-dependent: at 26 {degrees}C, higher tissue PFAS concentrations were associated with elevated standard and maximum metabolic rates (SMR and MMR), maintaining aerobic scope (AS). At 28.5 {degrees}C, SMR remained stable while MMR and AS declined with rising PFAS, indicating less oxygen for energetically demanding activities. Despite unchanged swimming and reproductive outputs, an increased hepatosomatic index with increasing tissue PFAS concentrations and altered PFAS distribution suggest detoxification costs. These findings indicate that increases in mean water temperature are likely to exacerbate contaminant stress, with consequences for coastal fish population resilience and offspring development. PFAS risk assessment should consider co-stressors under projected warming. SynopsisLimited research addresses how temperature affects PFAS toxicokinetics and toxicity. This study shows that warming reshapes tissue PFAS concentrations and distribution, and influences fish energy-allocation trade-offs.

physiology↗

bioRxiv2024

Rates of evolution differ between cell types identified by single-cell RNAseq in threespine stickleback

Rates of evolutionary change vary by gene. While some broad gene categories are highly conserved with little divergence over time, others undergo continuous selection pressure and are highly divergent. Here, we combine single-cell RNA sequencing (scRNAseq) with evolutionary genomics to understand whether certain cell types exhibit faster evolutionary divergence (using their characteristic genes), than other types of cells. Merging scRNAseq with population genomic data, we show that cell types differ in the rate at which their characteristic genes evolve, as measured by allele frequency divergence among many populations (FST) and between species (dN/dS ratios). Neutrophils, B cells, and fibroblasts exhibit elevated FST at characteristic genes, while eosinophils in the intestine and thrombocytes in the head kidney exhibit lower FST than the average for 1000 random genes. Gene network centrality also differed between immune- and non-immune-associated genes, and closeness centrality was positively related to gene FST. These results highlight the value of merging single cell RNA sequencing technology with evolutionary population genomic data, and reveal that genes which define immune cell types exhibit especially rapid evolution.

evolutionary biology↗

bioRxiv2023

Opening a can of worms: a test of the coinfection facilitation hypothesis

Parasitic infections are a global occurrence and impact the health of many species. Coinfections, where two or more species of parasite are present in a host, are a common phenomenon across species. Coinfecting parasites can interact directly, or indirectly via their manipulation of (and susceptibility to) the immune system of their shared host. Helminths, such as the cestode Schistocephalus solidus, are well known to suppress immunity of their host (threespine stickleback, Gasterosteus aculeatus), potentially facilitating other parasite species. Yet, hosts can evolve a more robust immune response (as seen in some stickleback populations), potentially turning facilitation into inhibition. Using wild-caught stickleback from 21 populations with non-zero S. solidus prevalence, we tested an a priori hypothesis that S. solidus infection facilitates infection by other parasites. Consistent with this hypothesis, individuals with S. solidus infections have 18.6% higher richness of other parasites, compared to S. solidus-uninfected individuals from the same lakes. This facilitation-like trend is stronger in lakes where S. solidus is particularly successful but is reversed in lakes with sparse and smaller cestodes (indicative of stronger host immunity). These results suggest that a geographic mosaic of host-parasite coevolution might lead to a mosaic of between-parasite facilitation/inhibition effects.

ecology↗

bioRxiv2022

Identification of Transient Intermediates During Spliceosome Activation by Single Molecule Fluorescence Microscopy

Spliceosome activation is the process of creating the catalytic site for RNA splicing and occurs de novo on each intron following spliceosome assembly. Dozens of factors bind to or are released from the activating spliceosome including the Lsm2-8 heteroheptameric ring that binds the U6 small nuclear RNA (snRNA) 3-end. Lsm2-8 must be released to permit active site stabilization by the Prp19-containing complex (NineTeen Complex, NTC); however, little is known about the temporal order of events and dynamic interactions that lead up to and follow Lsm2-8 release. We have used colocalization single molecule spectroscopy (CoSMoS) to visualize Lsm2-8 dynamics during activation of yeast spliceosomes. Lsm2-8 is recruited as a component of the tri-snRNP and is released after integration of the Prp19-containing complex (NineTeen Complex, NTC). Despite Lsm2-8 and the NTC being mutually exclusive in existing cryo-EM structures of yeast B complex spliceosomes, we identify a transient intermediate containing both [Formula] and provide a kinetic framework for its formation and transformation during activation. Prior to [Formula] assembly, the NTC rapidly and reversibly samples the spliceosome suggesting a mechanism for preventing NTC sequestration by defective spliceosomes that fail to properly activate. In complementary ensemble assays, we show that a base-pairing dependent ternary complex can form between Lsm2-8 and U2 and U6 helix II RNAs. Together our data suggest a Hfq-like function for Lsm2-8 in maintaining U2/U6 helix II integrity before it can be transferred to the NTC by transient formation of the [Formula] spliceosome. Significance StatementThe spliceosome active site is created de novo during activation and involves numerous conformational and compositional changes. Here, we define a kinetic pathway for yeast spliceosome activation using single molecule fluorescence that includes transient intermediates not previously identified. Real-time measurements allow us to uncover rapid, reversible sampling interactions of the NineTeen Complex (NTC) that may prevent its accumulation on defective spliceosomes. By analogy with bacterial Hfq, we propose that the homologous Lsm2-8 proteins stabilize U2/U6 helix II during activation before the helix is transferred to the NTC in a short-lived spliceosome containing both Lsm2-8 and the NTC. Our data demonstrate how single molecule studies of activation can reveal kinetically-competent intermediates and complement cryo-EM studies of stalled or inhibited complexes.

biochemistry↗