Biology subjects

Cheetham, C. E. J.

Publications and source records attributed to Cheetham, C. E. J..

6 recordsLinked to original sources

bioRxiv2025

Immature olfactory sensory neurons provide complementary input in the healthy olfactory system

Adult neurogenesis of olfactory sensory neurons (OSNs) provides the unique opportunity to understand how new neurons functionally integrate into existing circuitry and contribute to behaviors. Previous studies have shown that immature OSNs express odorant receptors, form dendritic knobs with short cilia, and project their axons into the olfactory bulb (OB) to form functional synapses. Furthermore, a previous study found that immature OSNs respond selectively to odorants and exhibit graded responses in a higher odorant concentration range than mature OSNs. Finally, this study also showed that, in mice that lack mature OSNs, sensory input from immature OSNs can mediate odor detection and discrimination. What remains unknown is how these immature OSNs contribute to odor-guided behavior in the healthy, intact olfactory system. Here we show that chemogenetically silencing immature OSNs impairs odor detection ability in a buried food assay. Furthermore, immature OSN silencing reduces the amplitude of odor-evoked dendritic calcium responses in OB neurons in vivo. Together, these findings suggest that immature OSNs provide distinct odor input that complements mature OSN input to contribute to odor-guided behaviors in the healthy, intact olfactory system.

neuroscience↗

bioRxiv2025

Longitudinal Assessment of Fluorescence Stability Shows Fluorescence Intensity Decreases Over Time: Implications for Fluorescence Microscopy Studies

Immunohistochemistry (IHC) is one of the most widely used techniques across basic, translational, and clinical sciences. Key considerations need to be made to achieve reliable and robust IHC staining, however what has been understudied is the stability of IHC signal intensity over time. Changes in signal intensity over time have significant implications for data analysis and interpretation and ultimately impact scientific conclusions. In order to explore changes in IHC signal, the stability of fluorescence intensity was assessed over the course of six weeks using widefield or confocal microscopy. Results indicate that fluorescence intensity can decrease over this time course and that whether this decrease occurs and to what extent is influenced by the selection of the primary antibody as well as that of the secondary antibody, primary-secondary antibody combination, and utilization of chemical staining versus IHC staining. This investigation reinforces best practices for imaging fluorescent staining to ensure accurate and reliable data collection, be it for cell counting, assessing protein expression levels, or marker colocalization.

neuroscience↗

bioRxiv2024

Regional deficits in endogenous regeneration of mouse olfactory sensory neuron axons

Postnatal neurogenesis occurs in only a few regions of the mammalian nervous system. Hence, neurons that are lost due to neurodegenerative disease, stroke, traumatic brain injury or peripheral neuropathy cannot be replaced. Transplantation of stem cell-derived neurons provides a potential replacement strategy, but how these neurons can be encouraged to functionally integrate into circuits remains a significant challenge. In the mammalian olfactory epithelium (OE), olfactory sensory neurons (OSNs) continue to be generated throughout life from basal stem cells and can be repopulated even after complete ablation. However, the specialized population of navigator OSNs that ensures accurate olfactory receptor-specific targeting of OSN axons to glomeruli in the olfactory bulb (OB) is only present perinatally. Despite this, some studies have reported complete regeneration of specific glomeruli, while others have found various degrees of recovery, following OSN cell death. Variability in the extent of both initial OSN ablation and subsequent repopulation of the OE, and the focus on anatomical recovery, leave the extent to which newly generated OSNs can reinnervate the OB unclear. Here, we employed the olfactotoxic drug methimazole (MMZ) to selectively ablate OSNs without damaging the basal stem cells that generate them, enabling us to assess the extent of functional recovery of OSN input to the OB in the context of complete OSN repopulation. We found profound deficits in the recovery of odor-evoked responses in OSN axons in the glomerular layer of the dorsal OB five weeks after OSN ablation, a time point at which OSNs are known to have repopulated the OE. Histological analysis of mature OSN axons in the OB at 10 and 20 weeks post-methimazole showed persistent region-specific deficits in OSN axon reinnervation of the dorsal and medial OB, with the dorsomedial region being particularly adversely affected. In contrast, reinnervation of the glomerular layer in lateral and ventral regions of the OB was essentially complete by 10 weeks post-MMZ. Hence, we have identified a region-specific deficit in OSN reinnervation of the mouse OB, which sets the stage to identify the mechanisms that mediate successful vs. unsuccessful axonal regeneration in an endogenous population of stem cell-derived neurons.

neuroscience↗

bioRxiv2024

Cell type- and layer-specific plasticity of olfactory bulb interneurons following olfactory sensory neuron ablation

Lifelong neurogenesis endows the mouse olfactory system with a capacity for regeneration that is unique in the mammalian nervous system. Throughout life, olfactory sensory neurons (OSNs) are generated from olfactory epithelium (OE) stem cells in the nose, while the subventricular zone generates neuroblasts that migrate to the olfactory bulb (OB) and differentiate into multiple populations of inhibitory interneurons. Methimazole (MMZ) selectively ablates OSNs, but OE neurogenesis enables OSN repopulation and gradual recovery of OSN input to the OB within six weeks. However, it is not known how OB interneurons are affected by this loss and subsequent regeneration of OSN input following MMZ treatment. We found that dopaminergic neuron density was significantly reduced 7-14 days post-MMZ but recovered substantially at 35 days. The density of parvalbumin-expressing interneurons was unaffected by MMZ; however, their soma size was significantly reduced at 7-14 days post-MMZ, recovering by 35 days. Surprisingly, we found a transient increase in the density of calretinin-expressing neurons in the glomerular and external plexiform layers, but not the granule cell layer, 7 days post-MMZ. This could not be accounted for by increased neurogenesis but may result from increased calretinin expression. At subsequent time points, calretinin neurons in all three layers showed reduced density at 14 days but recovered to baseline by 35 days. Together, our data demonstrate cell type- and layer-specific changes in OB interneuron density and morphology after MMZ treatment, providing new insight into the range of plasticity mechanisms employed by OB circuits during loss and regeneration of sensory input.

neuroscience↗

bioRxiv2022

CACNB4 overexpression decreases dendritic spine density in sex-specific manner

The canonical voltage-gated calcium channel (VGCC) subunit complex is comprised of the 1 subunit, the ion permeable channel, plus three auxiliary subunits: {beta}, 2{delta} and {gamma}. {beta} is the most extensively studied auxiliary subunit and is necessary for proper forward trafficking of the 1 subunit to the plasma membrane. 1 subunits mediate voltagedependent movement of calcium ions into the cytoplasm of neurons, including at dendritic sites, where increased intracellular calcium initiates signaling cascades that shape structural and functional plasticity of dendritic spines. Genetic studies strongly implicate calcium signaling dysfunction in the etiology of neurodevelopmental disorders including schizophrenia. Dendritic spine density (DSD) is significantly decreased in schizophrenia in primary auditory cortex where DSD is driven by loss of small spines, and small spine loss is associated with increased peptide levels of ALFDFLK found in the VGCC {beta} subunit {beta}4. Overexpessing CACNB4 to increase {beta}4 levels selectively reduced small spine density in cortical neuron cultures. The studies described herein set out to validate this in vitro observation in an intact mammalian system within a neurodevelopmental context. We overexpressed CACNB4 in neurodevelopment and assessed DSD and morphology in cerebral cortex of male and female mice at an adult timpoint. We then characterized {beta} protein levels and {beta}4 protein-protein interactions in male and female mouse cortex. Overexpression selectively reduced small dendritic spine density but this effect was present only in female mice and did not appear to result from estrous stage. Instead, the sex-dependent effect on DSD corresponded to sex differences in the {beta}4 interactome of male versus female mice: the VGCC {beta} subunit {beta}1b was significantly enriched in the {beta}4 interactome of brain tissue of male mice, and thus may have served to mitigate VGCC overexpression-mediated spine loss in male mice.

neuroscience↗

bioRxiv2021

Immature olfactory sensory neurons provide behaviorally useful sensory input to the olfactory bulb

Postnatal neurogenesis provides an opportunity to understand how newborn neurons integrate into circuits to restore function. Newborn olfactory sensory neurons (OSNs) wire into highly organized olfactory bulb (OB) circuits throughout life, enabling lifelong plasticity and regeneration. Immature OSNs form functional synapses capable of evoking firing in OB projection neurons but what contribution, if any, they make to odor processing is unknown. Here, we show that immature OSNs provide odor input to the OB, where they form monosynaptic connections with excitatory neurons. Importantly, immature OSNs respond as selectively to odorants as mature OSNs and provide information about high odorant concentrations at which mature OSN responses are already maximal, suggesting that immature and mature OSNs provide distinct odor input streams. Furthermore, mice can successfully perform odor detection and discrimination tasks using sensory input from immature OSNs alone. Together, our findings suggest that immature OSNs play a previously unappreciated role in olfactory-guided behavior.

neuroscience↗