Biology subjects

Floyd, C.

Publications and source records attributed to Floyd, C..

6 recordsLinked to original sources

bioRxiv2025

A Porcine Model of Intervertebral Disc Injury Recapitulates Human Discogenic Pain via Notochordal Cell Loss and Pain-inducing Nucleus Pulposus Cell Emergence

Lower back pain (LBP) is one of the most common causes of disability, with up to 40% of LBP cases attributed to intervertebral disc (IVD) degeneration. While small animal models are widely used to study IVD and LBP, the small size of their IVDs limits translational and biological relevance. Large animal models more accurately emulate human disease; however, methods of measuring LBP are not well established. Pigs were also considered unfit for LBP research, due to notochordal cells (NCs) persistence through life, unlike humans. We developed a comprehensive porcine model with quantitative measure of discogenic pain via biobehavioral testing (BBT), MRI, and multi-omics tissue analysis of IVD and DRGs. MRI demonstrated the progression of IVD degeneration beginning at 4 weeks post-injury. BBTs showed the development of significant pain responses by week 4 post-injury, supported by transcriptomics of injury matched DRGs. Single cell transcriptomics, trajectory and cell-cell communication analyses suggest that, with injury, NCs are differentiating to nucleus pulposus cells (NPCs). Furthermore, NPCs showed upregulation of cellular stress, neural outgrowth, and inflammation pathway, consistent with pain-inducing distress signals found in human samples. This study establishes novel MRI and BBT-based methods for quantifying LBP in pigs and supports its translational relevance to human discogenic LBP. The identification of LBP-associated clusters mirrors our previous finding in humans. Moreover, the shift of NC to NPC phenotype further supports that the porcine model is relevant to human pathology, as the injury induced accelerated aging and loss of NCs with IVD degeneration and discogenic pain.

developmental biology↗

bioRxiv2025

Light-induced reversible assembly and actuation in ultrafast Ca2+-driven chemomechanical protein networks

Programming rapid, repeatable motions in soft materials has remained a challenge in active matter and biomimetic design. Here, we present a light-controlled chemomechanical network based on Tetrahymena thermophila calcium-binding protein 2 (Tcb2), a Ca2+-sensitive contractile protein. These networks--driven by Ca2+-triggered structural rearrangements--exhibit dynamic selfassembly, spatiotemporal growth, and contraction rates comparable to actomyosin systems. By coupling light-sensitive chelators for optically triggered Ca2+ release, we achieve precise growth and repeatable mechanical contractility of Tcb2 networks, revealing emergent phenomena such as boundary-localized active regions and density gradient-driven reversals in motion. A coupled reaction-diffusion and elastic model explains these dynamics, highlighting the interplay between chemical network assembly and mechanical response. We further demonstrate active transport of particles via network-mediated forces in vitro and implement reinforcement learning to program seconds-scale spatiotemporal actuation in silico. These results establish a platform for designing responsive active materials with rapid chemomechanical dynamics and tunable optical control, with applications in synthetic cells, sub-cellular force generation, and programmable biomaterials.

bioengineering↗

bioRxiv2024

Fishnet mesh of centrin-Sfi1 drives ultrafast calcium-activated contraction of the giant cell Spirostomum ambiguum

Spirostomum is a giant unicellular ciliate that contracts to a quarter of its body length in less than five milliseconds, achieving an order of magnitude higher fractional shortening rate than actomyosin-based systems. This ultrafast contraction is powered by myonemes, calcium-activated protein networks at the cortex whose biochemical mechanism remain unclear. We quantify changes in cortical microtubules, membrane ruffles, and the fishnet-like myoneme mesh during contraction, and develop multiscale models that connect local myoneme shortening to whole-cell shape change. Centrin and an Sfi1 homolog co-localize with the myoneme by immunofluorescence and localize to the myoneme by immunogold electron microscopy. Coarse-grained mesh simulations reproduce the measured deformations and show that fishnet geometry, together with volume conservation, leads to uniform contraction. Finally, we reconstitute a Spirostomum centrin-Sfi1 repeat complex in vitro and measure calcium-dependent compaction and self-association, supporting a molecular basis for myoneme contractility. Together, these results support a multiscale model in which calcium-responsive centrin- Sfi1 structures are the central contractile element in Spirostomum and suggest design principles for fast, calcium-triggered, chemomechanical contractile networks that operate without actomyosin or ATP. SIGNIFICANCE STATEMENTMany cells change shape using actomyosin, but some protists contract using calcium-activated protein networks called myonemes. We combine quantitative imaging, electron microscopy, multiscale modeling, and in vitro reconstitution to link molecular-scale mechanisms to the millisecond shortening of the giant ciliate Spirostomum. Centrin and an Sfi1 homolog co-localize in a fishnet-like cortical mesh, and simulations show that this geometry can reproduce the observed whole-cell shape change under volume conservation. Purified centrin-Sfi1 complexes undergo calcium-dependent compaction and self-association, supporting a protein-scale switch that can drive myoneme contraction. These results connect calcium signaling to whole-cell mechanics and suggest principles for designing fast, ATP-independent bioin-spired actuators and synthetic cellular machinery.

cell biology↗

bioRxiv2023

Foliar inoculation of Phyllachora maydis into corn induces infection and local spread in field environments

Tar spot of corn (Zea mays L.) is a significant disease in the United States and Canada caused by Phyllachora maydis, an obligate biotroph fungus. However, field research critical for understanding, managing, and mitigating the disease has been hindered by a need for methods to inoculate corn with P. maydis in field environments. In this study, we developed a method to initiate tar spot in field settings using inoculations of corn leaves with P. maydis inoculum that had been stored at -20 {degrees}C for 10 months. Stromata of P. maydis were observed 19 days after inoculation (dai), and the spread of tar spot was initially detected locally from the infection area 39 to 41 dai. Tar spot was not present in the fields beyond the inoculated area or localized spread area, signifying that the establishment of the disease resulted solely from inoculations. This study enhances our understanding of inoculation and infection of corn with P. maydis and tar spot development in field environments. The results will aid new research into understanding the corn tar spot pathosystem and improving management strategies.

plant biology↗

bioRxiv2022

A unified model for the dynamics of ATP-independent ultrafast contraction

In nature, several ciliated protists possess the remarkable ability to execute ultrafast motions using protein assemblies called myonemes, which contract in response to Ca2+ ions. Existing theories, such as actomyosin contractility and macroscopic biomechanical latches, do not adequately describe these systems, necessitating new models to understand their mechanisms. In this study, we image and quantitatively analyze the contractile kinematics observed in two ciliated protists (Vorticella sp and Spirostomum sp), and, based on the mechanochemistry of these organisms, we propose a minimal mathematical model that reproduces our observations as well as those published previously. Analyzing the model reveals three distinct dynamic regimes, differentiated by the rate of chemical driving and the importance of inertia. We characterize their unique scaling behaviors and kinematic signatures. Besides providing insights into Ca2+-powered myoneme contraction in protists, our work may also inform the rational design of ultrafast bioengineered systems such as active synthetic cells.

biophysics↗

bioRxiv2020

Immunoresolvents Support Skeletal Myofiber Regeneration via Actions on Myeloid and Muscle Stem Cells

Specialized pro-resolving mediators (SPMs) actively limit inflammation and expedite its resolution. Here we profiled intramuscular lipid mediators following injury and investigated the role of SPMs in skeletal muscle inflammation and repair. Both eicosanoids and SPMs increased following myofiber damage induced by intramuscular injection of barium chloride or functional overload. Daily systemic administration of resolvin D1 (RvD1) limited the degree and duration of inflammation, enhanced regenerating myofiber growth, and improved recovery of muscle strength. RvD1 suppressed inflammatory cytokines, enhanced polymorphonuclear cell clearance, modulated muscle stem cells, and polarized macrophages to a more pro-regenerative subset. RvD1 had minimal direct impact on in-vitro myogenesis but directly suppressed myokine production and stimulated macrophage phagocytosis, showing that SPMs influence modulate both infiltrating myeloid and resident muscle cells. These data reveal the efficacy of immunoresolvents as a novel alternative to classical anti-inflammatory interventions in the management of muscle injuries to modulate inflammation while stimulating tissue repair.

immunology↗