Biology subjects

Farmer, K.

Publications and source records attributed to Farmer, K..

5 recordsLinked to original sources

bioRxiv2026

Scn2a-deficient mice exhibit serotonergic dysfunction and altered behavioral responses to psilocybin

Autism spectrum disorder (ASD) is a prominent neurodevelopmental disorder affecting approximately 3.2% of children in the United States. Although ASD has traditionally been considered a polygenic disorder, advances in genetic testing have identified individual genes that can contribute to its development. Large-scale whole-exome sequencing has identified variants in SCN2A, which encodes the alpha subunit of the voltage-gated sodium channel Nav1.2, as a leading monogenic cause of ASD. Social deficits are a core feature of ASD, and the serotonergic system has been implicated in the regulation of social behavior. Recent studies have demonstrated that serotonergic psychedelics, such as psilocybin, can increase sociability in mouse models of ASD. However, whether underlying genetic alterations associated with ASD influence behavioral responses to psilocybin remains poorly understood. Therefore, we investigated how Scn2a deficiency affects behavioral responses to psilocybin and whether these differences are accompanied by alterations in the serotonergic system. We found that Scn2a-deficient mice exhibited differential responses to psilocybin compared to wild-type (WT) mice. Specifically, psilocybin increased sociability in Scn2a-deficient mice without affecting anxiety-like behavior, whereas WT mice exhibited decreased anxiety-like behavior without increased sociability. Further behavioral evaluation revealed a reduced head twitch response in Scn2a-deficient mice following psilocybin administration compared to WT mice. To further investigate these differences, we examined serotonin levels and receptor expression in the medial prefrontal cortex (mPFC), a brain region implicated in social behavior and psychedelic action. Although baseline serotonin levels in the mPFC did not differ between genotypes, Scn2a-deficient mice exhibited altered serotonin receptor expression. We further characterized the serotonergic system by evaluating neuronal activity in the Dorsal Raphe Nucleus, a major source of serotonergic projections to the mPFC, and found increased spontaneous firing in Scn2a-deficient mice. Together, these findings highlight serotonergic alterations associated with SCN2A deficiency and the potential for serotonergic interventions to alleviate social deficits associated with SCN2A-related ASD.

neuroscience↗

bioRxiv2026

Gene therapy with doxycycline-controlled expression of human Kv1.1 reduces neuronal excitability and increases sociability of Scn2a-deficient mice

Genetic loss-of-function (LoF) variants in SCN2A, a gene encoding the voltage-gated sodium channel Nav1.2, have been identified as one of the foremost monogenic causes of autism spectrum disorder (ASD). ASD encompasses a broad spectrum of behavioral phenotypes, with impaired sociability as a core characteristic. We have established Scn2a-deficient mice (Scn2agt/gt) to model Scn2a-related ASD and found that this model recapitulates social impairment, exhibiting severe social deficits. Scn2agt/gt mice exhibit neuronal hyperexcitability and a marked global reduction in potassium channel expression, which plays a crucial role in maintaining the resting membrane potential and repolarizing neurons after an action potential. Among these downregulated potassium channels, potassium voltage-gated channel subfamily A member 1 (Kv1.1) was one of the most affected. To explore whether Kv1.1 could be a potential therapeutic target in SCN2A-related ASD, we evaluated the in vivo efficacy of a genetic construct driven by the CaMKII promoter that allows for exogenous expression of human Kv1.1 (hKv1.1) in principal neurons. In Scn2agt/gt mice, we found that hKv1.1 expression normalizes neuronal hyperexcitability. Importantly, doxycycline-induced hKv1.1 expression enhances sociability in Scn2a-deficient mice without influencing social behavior in wild-type mice, and this effect was reversed upon doxycycline withdrawal. Overall, we demonstrate the successful use of an inducible AAV-mediated gene delivery system to supplement hKv1.1 expression to mitigate neuronal hyperexcitability and ameliorate social impairments in a mouse model of SCN2A-related ASD. These findings highlight the contribution of Kv1.1 to SCN2A-associated pathophysiology and its potential as a therapeutic target for severe social deficits.

neuroscience↗

bioRxiv2024

Unique nigral and cortical pathways implicated by epigenomic and transcriptional analyses in a rotenone rat model of Parkinson's disease

Pesticide exposure is increasingly recognised as a potential environmental factor contributing to the onset of idiopathic Parkinsons disease, yet the molecular mechanisms underlying this connection remain unclear. This study aims to explore how pesticide exposure disrupts key brain regions involved in Parkinsons disease pathology by reshaping gene regulatory landscapes. Using the well-established rotenone rat model of the disease, we performed H3K27ac ChIP-sequencing to profile active regulatory elements in the substantia nigra and cortex. In this model, rotenone distributes uniformly throughout the brain, and the degree of complex I inhibition is equivalent in cortical and substantia nigra neurons. Despite the uniformity of complex I inhibition, we identified widespread epigenomic differences, with brain region specific acetylation patterns associated with rotenone exposure. We showed consistent changes in transcriptomic activity by RNA-sequencing. Our results indicate there is a strong immune response to rotenone localised to the substantia nigra and highlight an enrichment of immune-related motifs in this brain region, suggesting that the immune response is at least partially driven by gene regulatory mechanisms. We also noted an increase in C1q complement pathway activity in the substantia nigra. In contrast, we identified widespread dysregulation of synaptic function at the gene regulatory level in the cortex of these same rats. Our results highlight a role for gene regulatory mechanisms potentially mediating the effects of pesticide exposure, driving region-specific functional responses in the brain that may contribute to the pathology and selective vulnerability that characterise Parkinsons disease.

genomics↗

bioRxiv2024

15-Lipoxygenase-Mediated Lipid Peroxidation Regulates LRRK2 Kinase Activity

Mutations in leucine-rich repeat kinase 2 (LRRK2) that increase its kinase activity are strongly linked to genetic forms of Parkinsons disease (PD). However, the regulation of endogenous wild-type (WT) LRRK2 kinase activity remains poorly understood, despite its frequent elevation in idiopathic PD (iPD) patients. Various stressors such as mitochondrial dysfunction, lysosomal dyshomeostasis, or vesicle trafficking deficits can activate WT LRRK2 kinase, but the specific molecular mechanisms are not fully understood. We found that the production of 4-hydroxynonenal (4-HNE), a lipid hydroperoxidation end-product, is a common biochemical response to these diverse stimuli. 4-HNE forms post-translational adducts with Cys2024 and Cys2025 in the kinase activation loop of WT LRRK2, significantly increasing its kinase activity. Additionally, we discovered that the 4-HNE responsible for regulating LRRK2 is generated by the action of 15-lipoxygenase (15-LO), making 15-LO an upstream regulator of the pathogenic hyperactivation of LRRK2 kinase activity. Pharmacological inhibition or genetic ablation of 15-LO prevents 4-HNE post-translational modification of LRRK2 kinase and its subsequent pathogenic hyperactivation. Therefore, 15-LO inhibitors, or methods to lower 4-HNE levels, or the targeting of Cys2024/2025 could provide new therapeutic strategies to modulate LRRK2 kinase activity and treat PD.

neuroscience↗

bioRxiv2021

Neuronal NADPH oxidase in Parkinson disease pathogenesis

Mitochondrial dysfunction and oxidative stress are strongly implicated in the pathogenesis of Parkinsons disease (PD) and there is evidence that mitochondrially-generated superoxide can activate NADPH oxidase 2 (NOX2), which is a major enzymatic generator of superoxide. Although NOX2 has been examined in the context of PD, previous studies have focused on microglial function; the role of neuronal NOX2 in PD pathogenesis remains to be defined. Here we devised and validated a proximity ligation assay for NOX2 activity and demonstrated that in human PD and 2 models thereof, neuronal NOX2 is highly active in substantia nigra dopamine neurons. Further, NOX2 activity is responsible for accumulation, post-translational modification and oligomerization of -synuclein as well as activation of leucine-rich repeat kinase 2 (LRRK2). Administration of a brain-penetrant, specific NOX2 inhibitor prevented NOX2 activation and its downstream effects in vivo in a rat model of PD. We conclude that neuronal NOX2 is a major contributor to oxidative stress in PD, to -synuclein pathology and to LRRK2 activation in idiopathic PD. In this context, NOX2 inhibitors hold potential as a disease-modifying therapy in PD. SummaryIn dopamine neuron, NADPH oxidase isoform 2 amplifies the oxidative stress-related pathogenic cascade in Parkinsons disease

neuroscience↗