Biology subjects

O'Connell, C.

Publications and source records attributed to O'Connell, C..

4 recordsLinked to original sources

bioRxiv2026

Brain-wide mapping and synaptic localization of C1QL3 using a novel epitope-tagged knock-in mouse

Synapse formation and function are coordinated spatially and temporally by a host of synaptic proteins that regulate neuronal signaling, synapse specificity, and plasticity; many of which are implicated in neuropsychiatric disorders. Members of the C1q/TNF superfamily function as synaptic organizers, shaping synapse assembly and maintenance. Among them, C1QL3 plays a putative role in trans-synaptic adhesion and modulation of synaptic strength, but the lack of a reliable antibody to detect it has severely limited the ability to map its endogenous localization and study its biochemical properties. Here, we present a novel epitope-tagged knock-in mouse line (C1ql32HA), in which two hemagglutinin (HA) epitopes were inserted near the N-terminus of the endogenous C1QL3 protein. This model enables purification, detection, and subcellular localization of native C1QL3 protein (C1QL3-2HA) with high specificity, eliminating the need for overexpression or custom antibodies. We validated that C1ql32HA mice maintain normal mRNA expression, biochemical properties, and behavior. Using native PAGE, we determined the endogenous oligomeric state of C1QL3-2HA. Brain-wide light-sheet microscopy uncovered an expanded neuroanatomical map of C1QL3-2HA expression, including newly identified populations in cortical and subcortical regions as well as the retina. Dual immunohistochemistry confirmed cell type-specific expression patterns, and super-resolution STED microscopy localized C1QL3-2HA to hippocampal mossy fiber synapses, positioned between pre- and post-synaptic markers, supporting its hypothesized role in trans-synaptic complexes. This knock-in mouse line is a powerful tool for studying the anatomical, molecular, and synaptic biology of C1QL3 in all cellular/tissue contexts, enabling future studies into its potential roles in the nervous system and beyond.

neuroscience↗

bioRxiv2025

Genetic diversity of Collaborative Cross mice enables the establishment of a novel Chlamydia muridarum female genital tract infection model

Chlamydial infection in women displays wide variation in bacterial burden, persistence, and risk of upper genital tract pathology, yet the host genetic factors underlying this heterogeneity remain poorly defined. We evaluated genital tract infection with Chlamydia muridarum across 20 Collaborative Cross (CC) strains, a recombinant inbred mouse panel that captures broad genetic diversity with high within-strain reproducibility. CC strains exhibited striking differences in early bacterial burden, time to clearance, and oviduct pathology, including prolonged low-inflammatory infections and burden-pathology discordance that mirror key features of human disease. Heritability analyses demonstrated that host genetics accounted for most of the variation observed in Day 7 bacterial burden and pathological outcomes. Genome-wide scans identified suggestive quantitative trait loci associated with both traits. Genes within the burden-associated locus converged on host pathways implicated in chlamydial intracellular growth, including membrane dynamics and lipid metabolism, ubiquitin signaling, host cell survival mechanisms, and immune regulatory signaling. In contrast, genes within the pathology-associated locus were enriched for pathways regulating inflammatory cell recruitment, inflammasome activation, and tissue remodeling, processes central to genital tract damage following infection. Cervical transcriptional profiling further revealed strain-dependent innate and adaptive immune programs associated with bacterial burden and disease phenotype. Together, these findings establish the CC as a powerful platform for dissecting the genetic architecture of chlamydial immunopathogenesis, and for improving preclinical evaluation of vaccines and therapeutics.

immunology↗

bioRxiv2024

Synaptic Proteomes of Cortical Interneuron Classes Revealed by Antibody Directed Proximity Labeling.

Subtypes of inhibitory interneurons play diverse roles within neural circuits in cerebral cortex. Defining the molecular underpinnings of interneuron functions within cortical circuits will require identification of interneuron synaptic proteomes. In this study, we first combined genetically directed expression of tdTomato-synaptophysin with antibody-directed proximity labeling and tandem mass spectrometry to identify synaptic proteomes of three major interneuron classes in mouse cortex: parvalbumin (PV), somatostatin (SS), and vasoactive intestinal peptide (VIP). After stringent filtering we identified 581 proteins: 228 identified in all cell classes and 353 in one or two of three classes. The PV class had the largest number of uniquely identified proteins (141), followed by VIP (30) and SST (20). Consistent with previously reported electrophysiological evidence, PV presynaptic proteomes were enriched for NMDA receptor subunits and scaffolding proteins. We used antibodies against synaptotagmin 2 (Syt2), a presynaptic protein present at PV synapses, to confirm NMDAR localization, and to find that the mu-opioid receptor agonist buprenorphine rapidly caused reorganization of the PV presynaptic proteome. Overall, our results reveal proteomes of PV, SST, and VIP interneurons in cortex that likely underlie distinct and dynamic interneuron synaptic properties.

neuroscience↗

bioRxiv2023

Model matters: Differential outcomes in traumatic optic neuropathy pathophysiology between blunt and blast-wave mediated head injuries.

Over 3 million people in the United States live with long-term disability as a result of a traumatic brain injury (TBI). The purpose of this study was to characterize and compare two different animal models of TBI (blunt head trauma and blast TBI) to determine common and divergent characteristics of these models. With recent literature reviews noting the prevalence of visual system injury in animal models of TBI, coupled with clinical estimates of 50-75% of all TBI cases, we decided to assess commonalities, if they existed, through visual system injury. Blast, repeat blast, and blunt injury were induced in adult male mice to observe and quantify visual deficits. Retinal ganglion cell loss and axonal degeneration in the optic tract, superior colliculus, and lateral geniculate nuclei were examined to trace injury outcomes throughout major vision-associated areas. Optokinetic response, immunohistochemistry, and western blots were analyzed. Where a single blunt injury produces significant visual deficits a single blast injury appears to have less severe visual consequences. Visual deficits after repeat blasts are similar to a single blast. Single blast injury induces contralateral damage to right optic chiasm and tract whereas bilateral injury follows a single blunt injury. Repeat blast injuries are required to see degeneration patterns in downstream regions similar to the damage seen in a single blunt injury. This finding is further supported by Amyloid Precursor Protein (APP) staining in injured cohorts. Blunt injured groups present with staining 1.2 mm of the optic nerve, indicating axonal breakage closer to the optic chiasm. In blast groups, APP was identifiable in a bilateral pattern only in the geniculate nucleus. Evidence for unilateral neuronal degeneration in brain tissue with bilateral axonal ruptures are pivotal discoveries in this model differentiation. Analysis of the two injury models suggest there is a significant difference in the histological outcomes dependent on injury type, though visual system injury is likely present in more cases than are currently diagnosed clinically.

neuroscience↗