Biology subjects

Kuhn, N. C.

Publications and source records attributed to Kuhn, N. C..

8 recordsLinked to original sources

bioRxiv2026

Loss of autism-associated gene wac alters social behavior and identifies cho-1 as a modulator of cholinergic signaling in C. elegans

WAC is a chromatin-associated regulatory protein involved in transcriptional control and has been identified as an autism-associated gene in human genetic studies. However, its functional role in regulating behavior and synaptic processes remains incompletely understood. Using Caenorhabditis elegans, we investigated the consequences of wac deficiency on food-associated social behavior, growth-associated phenotypes, and cholinergic pathway function. wac-deficient worms showed a marked reduction in food-leaving behavior, supporting impaired behavioral responsiveness to food-associated environmental cues, while aggregation behavior was not significantly altered. PHX2587 wac deletion mutant worms also exhibited reduced body length, decreased pharyngeal pumping, and shortened lifespan, indicating broader growth and physiological impairment. Stage-resolved analysis of cholinergic pathway genes revealed stage-associated transcriptional changes, with coordinated upregulation of multiple presynaptic and postsynaptic cholinergic components (ace-1, cha-1, cho-1, lev-1, lev-10, unc-17, unc-29, unc-38, and unc-50) emerging most prominently at the young adult stage. Functional RNAi analysis further identified cho-1, which encodes the high-affinity presynaptic choline transporter, as a genotype-specific modifier of cholinergic sensitivity in PHX2587 worms. Importantly, cho-1 RNAi not only reduced aldicarb hypersensitivity but also partially suppressed the reduced body length phenotype and improved food-leaving behavior in PHX2587 worms, while having limited effects in wild-type N2. Together, these findings support a functional relationship between wac deficiency and cho-1-associated cholinergic modulation, suggesting that presynaptic choline transport contributes to selected behavioral and physiological consequences of wac loss. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/719318v2_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@cd8950org.highwire.dtl.DTLVardef@1f1e6adorg.highwire.dtl.DTLVardef@5f783dorg.highwire.dtl.DTLVardef@1cf0ed6_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

neuroscience↗

bioRxiv2026

Neurobehavioral impacts of the autism risk gene, WAC: Studies involving C. elegans and Mice

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by a broad spectrum of behavioral impairments. While multiple genetic and environmental factors are attributed to its cause, biological underpinnings are still poorly understood. We investigated an ASD-associated gene, WAC, for its neurobehavioral aspects using C. elegans and mice. Studies of C. elegans with wac gene deletions (wac-1.1 and wac-1.2) showed enhanced acetylcholine-associated behavior, as indicated by the aldicarb assay. No alteration in acetylcholine levels or acetylcholinesterase activity was observed. Upon further investigation, we found that the elevated cholinergic transmission resulted from increased activity of nicotinic acetylcholine receptors (nAChRs). Additionally, we observed reduced motility and dopamine-associated behaviors, along with a reduced ability to switch from crawling to swimming, a serotonin-dependent behavior. Upregulation in mRNA expression of the lev-1 gene was observed. Conversely, a feedback-counterbalancing response in the form of downregulated genes, acr-2, unc-17, unc-63, and unc-50, was also observed. Surprisingly, lev-1 RNAi did not reverse the enhanced cholinergic transmission in PHX2587 worms, indicating the involvement of other players. To validate our findings, we also assessed CHRNA7 levels in Wac+/- mice. While some genetic compensation was observed in heterozygous mice, we found a direct, inverse correlation between Wac mRNA expression and CHRNA7 levels in the mouse brain cortex, corroborating our findings from C. elegans. Overall, these studies indicate that wac gene deletion in C. elegans exhibits a neurotransmitter alteration that is relatable to ASD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=61 SRC="FIGDIR/small/709202v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1771dc4org.highwire.dtl.DTLVardef@1434b4eorg.highwire.dtl.DTLVardef@10525ecorg.highwire.dtl.DTLVardef@fcd8a9_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Brief report on differential toxicity of legacy and second-generation PFAS on dopaminergic neurons and mitochondria

Per/polyfluoroalkyl substances (PFAS) are anthropogenic chemicals that have shown extensive usage. Owing to widespread use and resistance to environmental degradation, they have become a hazard with respect to the environment and human health. While the legacy PFAS are being phased out, they are being replaced by second-generation PFAS that are considered safer alternatives. However, the lack of information pertaining to the underlying mechanisms for legacy and especially second-generation PFAS exacerbates the risk. This study investigates legacy and second-generation PFAS to determine their individual effects on neurotoxicity and mitochondrial respiration. Legacy PFAS, perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and second-generation PFAS, GenX, and ADONA were employed, and studies were conducted using Caenorhabditis elegans and mitochondria isolated from Rat brain for Complex I to IV. It was found that legacy PFAS, PFNA, and PFDA were neurotoxic, with neurotoxicity proportional to chain length. PFOA, PFNA, and PFDA also exhibited significant inhibition to most of the mitochondrial complexes. Whereas in the case of second-generation PFAS ADONA, and GenX, it was only limited to the inhibition of Complex IV. GenX only exhibited neurodegeneration at very high doses. Our findings conclude that the legacy and second-generation PFAS might have significant neurotoxic implications. While the targets are similar to some extent, the mechanisms between the two classes are distinct. Our study the sets the stage to evaluate further the combined effect of PFAS (legacy and emergent) to fill in informational gaps pertaining to their safety.

pharmacology and toxicology↗

bioRxiv2025

γ-glutamyl-cysteine is a critical intermediate in glutathione-led amelioration of PFOS-neurotoxicity

Perfluorooctane sulfonate (PFOS) is one of the most prevalent PFAS. Earlier studies using Caenorhabditis elegans indicated that glutathione (GSH) ameliorates PFOS-induced neurodegeneration. This study investigates the GSH synthesis pathway to elucidate critical neuroprotective mechanisms. We assessed the effects of GSH precursors, cysteine, glutamic acid, and cysteine + glutamic acid, and of the intermediate {gamma}-glutamyl-cysteine ({gamma}-Glu-Cys), on PFOS neurotoxicity. While cysteine showed slight neuroprotection, other GSH precursors, glutamate, and cysteine + glutamate did not demonstrate beneficial effects. However, the crucial GSH synthesis intermediate, {gamma}-Glu-Cys, conferred neuroprotection comparable to GSH. Notably, no changes were observed in the gene or protein expression of GSH synthesis enzymes in C. elegans and SH-SY5Y cells, respectively. Further, testing of the alternative pathway for 5-oxoproline-mediated GSH synthesis revealed that it is not involved in {gamma}-glutamyl-cysteine-mediated neuroprotection. Paradoxically, 5-oxoproline supplementation was neurotoxic, plausibly due to glutamate toxicity. Further, we tested the effect of acute PFOS exposure on mitochondrial complexes I, II, III, and IV. We observed significant inhibition of enzyme activity in mitochondrial complexes II, III, and IV. Next, we tested whether GSH and {gamma}-Glu-Cys could rescue PFOS-induced enzyme inhibition. We found that while both GSH and {gamma}-Glu-Cys could rescue enzyme inhibition in complex III, the rescuing effect was altogether absent for complex IV. Overall, our findings confirmed that both GSH and {gamma}-Glu-Cys can rescue PFOS-induced neurodegeneration and mitochondrial enzyme affliction. This study effectively uncovers a novel mechanism that addresses existing knowledge gaps pertaining to the role of the GSH pathway in curtailing PFOS neurotoxicity. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/657248v3_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1050eeborg.highwire.dtl.DTLVardef@11668e0org.highwire.dtl.DTLVardef@3f51ddorg.highwire.dtl.DTLVardef@1178865_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract {gamma}-glutamyl-cysteine is the critical intermediate in glutathione-modulated amelioration of PFOS-neurotoxicity Perfluorooctanesulfonate (PFOS) leads to dopaminergic cell loss in C. elegans. Glutathione (GSH) confers neuroprotection against PFOS neurotoxicity. Further investigation of the critical components involved in GSH biosynthesis identified that while precursors of GSH, Cysteine and glutamate fail to confer neuroprotection, only {gamma}-glutamyl-cysteine alleviates neuronal loss similar to GSH. C_FIG

neuroscience↗

bioRxiv2024

Parkinson's disease-associated shifts between DNA methylation and DNA hydroxymethylation in human brain

Epigenetic mechanisms are mediators of interactions between aging, genetics, and environmental factors in sporadic Parkinsons disease (PD). Multiple studies have explored the DNA modifications in PD, but few focus on 5-hydroxymethylcytosine (5-hmC), which is important in the central nervous system and sensitive to environmental exposures. To date, studies have not differentiated between 5-methylcytosine (5-mC) and 5-hmC or have analyzed them separately. In this study, we modeled paired 5-mC and 5-hmC data simultaneously. We identified 108 cytosines with significant PD-associated shifts between these marks in an enriched neuronal population from PD postmortem parietal cortex, within 83 genes and 34 enhancers associated with 67 genes. These data potentially link epigenetic regulation of genes related to LRRK2 and endolysosomal sort (RAB32 and AGAP1), and genes involved in neuroinflammation, the inflammasome, and neurodevelopment with early changes in PD and suggest that there are significant shifts between 5mC and 5hmC associated with PD in genes not captured by standard methods.

neuroscience↗

bioRxiv2024

Developmental origins of Parkinson's disease risk: perinatal exposure to the organochlorine pesticide dieldrin leads to sex-specific DNA modifications in critical neurodevelopmental pathways in the mouse midbrain

Epidemiological studies show that exposure to the organochlorine pesticide dieldrin is associated with increased risk of Parkinsons disease (PD). Animal studies support a link between developmental dieldrin exposure and increased neuronal susceptibility in the -synuclein preformed fibril (-syn PFF) and MPTP models in adult male C57BL/6 mice. In a previous study, we showed that developmental dieldrin exposure was associated with sex-specific changes in DNA modifications within genes related to dopaminergic neuron development and maintenance at 12 weeks of age. Here, we used capture hybridization-sequencing with custom baits to interrogate DNA modifications across the entire genetic loci of the previously identified genes at multiple time points - birth, 6 weeks, 12 weeks, and 36 weeks old. We identified largely sex-specific dieldrin-induced changes in DNA modifications at each time point that annotated to pathways important for neurodevelopment, potentially related to critical steps in early neurodevelopment, dopaminergic neuron differentiation, synaptogenesis, synaptic plasticity, and glial-neuron interactions. Despite large numbers of age-specific DNA modifications, longitudinal analysis identified a small number of DMCs with dieldrin-induced deflection of epigenetic aging. The sex-specificity of these results adds to evidence that sex-specific responses to PD-related exposures may underly sex-specific differences in disease. Overall, these data support the idea that developmental dieldrin exposure leads to changes in epigenetic patterns that persist after the exposure period and disrupt critical neurodevelopmental pathways, thereby impacting risk of late life diseases, including PD.

neuroscience↗

bioRxiv2023

Developmental exposure to the Parkinson's disease-associated organochlorine pesticide dieldrin alters dopamine neurotransmission in α-synuclein pre-formed fibril (PFF)-injected mice

Parkinsons disease (PD) is the most common movement disorder and one of the fastest-growing neurological diseases worldwide. This increase outpaces the rate of aging and is most rapid in recently industrialized areas, suggesting the role of environmental factors. Consistent with this, epidemiological studies show an association between exposure to persistent organic pollutants and an increased risk of PD. When combined with post-mortem analysis and mechanistic studies, a role for specific compounds, including the organochlorine pesticide dieldrin, emerges. In mouse models, developmental dieldrin exposure causes male-specific exacerbation of neuronal susceptibility to MPTP and synucleinopathy. Specifically, our novel two-hit model combining developmental dieldrin exposure with the -synuclein (-syn) pre-formed fibril (PFF) model showed a male-specific exacerbation of PFF-induced increases in striatal dopamine (DA) turnover and motor deficits on the challenging beam 6 months post-PFF injection in male offspring developmentally exposed to dieldrin. Here, we hypothesized that alterations in DA handling contribute to the observed changes and assessed vesicular monoamine transporter 2 (VMAT2) function and DA release in this dieldrin/PFF two-hit model. Female C57BL/6 mice were exposed to 0.3 mg/kg dieldrin or vehicle every 3 days, starting at 8 weeks of age by feeding and continuing throughout breeding, gestation, and lactation. Male offspring from independent litters underwent unilateral, intrastriatal injections of -syn PFFs via stereotaxic surgery at 12 weeks of age and DA handling was assessed 4 months post-PFF injection via vesicular 3H-DA uptake assay and fast-scan cyclic voltammetry (FSCV). We observed no dieldrin-associated change in VMAT2 activity, but a dieldrin-induced increase in DA release in striatal slices in PFF-injected animals. These results suggest that developmental dieldrin exposure alters the dopaminergic response to synucleinopathy-triggered toxicity and supports our hypothesis that alterations in DA handling may underly the observed exacerbation of PFF-induced deficits in motor behavior and DA turnover. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=67 SRC="FIGDIR/small/545967v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@d679deorg.highwire.dtl.DTLVardef@db0d70org.highwire.dtl.DTLVardef@14f368dorg.highwire.dtl.DTLVardef@1868894_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2021

Parkinson's Disease-Associated, Sex-specific Changes in DNA Methylation at PARK7 (DJ-1), ATXN1, SLC17A6, NR4A2, and PTPRN2 in Cortical Neurons

Evidence for epigenetic regulation playing a role in Parkinsons disease (PD) is growing, particularly for DNA modifications. Approximately 90% of PD cases are due to a complex interaction between age, genes, and environmental factors, and epigenetic marks are thought to mediate the relationship between aging, genetics, the environment, and disease risk. To date, there are a small number of published genome-wide studies of DNA modifications in PD, but none accounted for cell-type or sex in their analyses. Given the hetereogeneity of bulk brain tissue samples and known sex differences in PD risk, progression, and severity, these are critical variables to account for. In this first genome-wide analysis of DNA methylation in an enriched neuronal population from PD post-mortem parietal cortex, we report sex-specific PD-associated methylation changes in PARK7 (DJ-1), SLC17A6 (VGLUT2), PTPRN2 (IA-2{beta}), NR4A2 (NURR1), and other genes involved in developmental pathways, neurotransmitter packaging and release, and axon and neuron projection guidance.

neuroscience↗