Biology subjects

Kunkhyen, T.

Publications and source records attributed to Kunkhyen, T..

5 recordsLinked to original sources

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↗

bioRxiv2023

Sexually dimorphic mechanisms of VGLUT-mediated protection from dopaminergic neurodegeneration

Parkinsons disease (PD) targets some dopamine (DA) neurons more than others. Sex differences offer insights, with females more protected from DA neurodegeneration. The mammalian vesicular glutamate transporter VGLUT2 and Drosophila ortholog dVGLUT have been implicated as modulators of DA neuron resilience. However, the mechanisms by which VGLUT2/dVGLUT protects DA neurons remain unknown. We discovered DA neuron dVGLUT knockdown increased mitochondrial reactive oxygen species in a sexually dimorphic manner in response to depolarization or paraquat-induced stress, males being especially affected. DA neuron dVGLUT also reduced ATP biosynthetic burden during depolarization. RNA sequencing of VGLUT+ DA neurons in mice and flies identified candidate genes that we functionally screened to further dissect VGLUT-mediated DA neuron resilience across PD models. We discovered transcription factors modulating dVGLUT-dependent DA neuroprotection and identified dj-1{beta} as a regulator of sex-specific DA neuron dVGLUT expression. Overall, VGLUT protects DA neurons from PD-associated degeneration by maintaining mitochondrial health.

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↗