Biology subjects

O'Brien, C. F.

Publications and source records attributed to O'Brien, C. F..

3 recordsLinked to original sources

bioRxiv2026

Spared corticospinal neurons activate an endogenous plasticity program after partial CNS injury

Functional recovery after incomplete spinal cord injury depends substantially on the capacity of anatomically spared neurons to remodel their connections, yet the molecular programs underlying this endogenous plasticity remain poorly understood. To identify and validate these mechanisms, we combined retrograde labeling, unilateral corticospinal tract injury, spatial transcriptomics, and human stem cell-derived neurons. Injured corticospinal neurons exhibited widespread downregulation with remaining activated pathways dominated by stress, cell death, and degenerative programs. In contrast, spared corticospinal neurons activated a coordinated pro-plasticity program characterized by metabolic, immune, and cytoskeletal remodeling together with selective suppression of growth-inhibitory signaling. Network and drug perturbation analyses identified ARHGEF12 suppression and vorinostat treatment as complementary target- and state-based strategies to enhance neurite regeneration in human neurons. Together, these findings define key components of endogenous plasticity and provide a framework for discovering therapeutic targets for neural repair.

neuroscience↗

bioRxiv2025

Rehabilitation drives functional reorganization of intact corticospinal-supraspinal projections following partial spinal cord injury

Spinal cord injury (SCI) disrupts corticospinal tract (CST) connectivity and impairs skilled voluntary movement. However, most human SCIs are anatomically incomplete, allowing spared CST pathways to engage in rehabilitation-mediated plasticity to promote functional recovery. How voluntary rehabilitation engages and reorganizes the supraspinal targets of the intact CST remains incompletely understood. Here, we combined unilateral pyramidotomy (uPyX) in male and female mice with continuous voluntary complex-wheel running to test whether fine motor-dependent rehabilitation drives supraspinal CST plasticity. uPyX mice rapidly resumed wheel running after a transient deficit. In contrast to lesion-only controls, rehabilitation significantly improved skilled forelimb performance on the horizontal ladder rung task. Immunohistochemical c-Fos labeling confirmed that complex-wheel running robustly activated the intact forelimb CST in motor cortex. Whole-brain CST projection mapping using intersectional viral vector tracing revealed targeted supraspinal reorganization localized to medullary motor nuclei. Three nuclei - the lateral paragigantocellular reticular nucleus (LPGi), gigantocellular reticular nucleus, alpha part (GiA), and ventral medullary reticular nucleus (MdV) - exhibited significant lesion- and/or rehabilitation-induced increases in CST innervation. Rehabilitation-driven CST sprouting correlated with regional c-Fos activation, indicating activity-dependent remodeling. Notably, CST projection density in the MdV, critical for skilled forelimb control, correlated with functional recovery. These findings identify a set of spinally-projecting medullary nuclei as key sites of rehabilitation-induced CST plasticity and highlight the MdV as a potential mediator of restored motor function. This work defines how voluntary rehabilitation reorganizes spared corticospinal pathways and provides targets for optimizing activity-based interventions after SCI. Significance StatementEffective rehabilitation after spinal cord injury (SCI) must harness the plasticity of spared motor pathways, yet the supraspinal circuits that support rehabilitation-mediated recovery remain unknown. Using a model that preserves voluntary motor engagement, we show that continuous fine motor-dependent rehabilitation activates intact corticospinal neurons and drives highly specific remodeling of their supraspinal terminals. Rehabilitation selectively strengthens CST inputs to motor regions of the medulla, particularly the ventral medullary reticular nucleus (MdV), and CST plasticity within this region predicts enhanced behavioral recovery. These findings highlight the MdV as a central locus by which rehabilitation re-establishes descending control of the impaired limb, providing mechanistic insight to guide targeted, circuit-based rehabilitation therapies for incomplete SCI.

neuroscience↗

bioRxiv2025

REVS: A New Open-Source Platform for High-Resolution Analysis of Rodent Wheel Running Behavior

BackgroundRodent wheel running is widely used in neuroscience and preclinical research to assess locomotor function, recovery post-trauma or disease, circadian rhythms, and exercise physiology. However, most existing wheel-running systems offer limited metrics, lack flexibility in hardware, or require costly proprietary software, reducing their usefulness for detailed behavioral phenotyping--especially in models of injury or rehabilitation. New methodWe developed REVS (Revolution Evaluation and Visualization Software), a low-cost, open-source hardware and software platform for analyzing and visualizing rodent wheel running behavior. REVS captures wheel revolutions using Hall effect sensors and computes 13 day-level behavioral metrics along with detailed bout-level data. Users can interactively explore high-resolution temporal features and export data in Open Data Commons (ODC)-compatible formats. REVS supports customizable wheel types, facilitating use in animals with motor and/or sensory impairments. ResultsWe validated REVS using a mouse model of partial spinal cord injury, where fine motor control is compromised. REVS detected impairments in 10 of 13 behavioral metrics post-injury, with varied recovery trajectories across measures. Principal component analysis revealed that recovery was closely linked to bout quality and intensity, rather than timing. Comparison with existing methodsUnlike commercial and open-source systems, REVS offers more detailed metrics, customizable wheel compatibility, seamless blending with common vivarium hardware, integrated data visualizations, and ODC-compatible data export. It also supports flexible analysis across individuals and groups. ConclusionsREVS provides a powerful, scalable tool for granular behavioral phenotyping in rodent studies, enhancing reproducibility and revealing insights into subtle locomotor changes associated with injury, recovery, and intervention. HighlightsO_LIREVS enables detailed analysis of voluntary wheel running in rodents C_LIO_LIThe platform combines low-cost hardware with open-source analysis software C_LIO_LIREVS computes 13 behavioral metrics across daily and bout-level timescales C_LIO_LIWe identified a unique lesion and recovery profile after partial spinal cord injury C_LIO_LIREVS supports ODC-compatible data export for transparency and reuse C_LI

neuroscience↗