Biology subjects

Margetts, A. V.

Publications and source records attributed to Margetts, A. V..

5 recordsLinked to original sources

bioRxiv2026

Morphine and methamphetamine trigger divergent post-transcriptional neuroimmune landscapes in the dorsal striatum

Opioid and methamphetamine use disorders (OUD and MUD) are characterized by enduring neural adaptations within brain reward circuitry, yet the cell-type-specific post-transcriptional mechanisms underlying these changes remain poorly understood. While microglia are essential for maintaining central nervous system homeostasis and modulating neuroinflammatory responses to drugs of abuse, their alternative splicing (AS) programs have not been defined in the context of addiction. This study characterized the microglial AS landscape in the mouse dorsal striatum during morphine and methamphetamine intravenous self-administration (IVSA), as well as following a 21-day period of abstinence. Analysis of RNA-sequencing data using rMATS and DEXSeq revealed that both drugs significantly dysregulate core splicing machinery, with skipped exons (SE) emerging as the most prevalent splicing event. Notably, morphine exposure induced a robust persistent splicing signature, comprising 736 exonic regions in 221 genes that remained altered through abstinence, whereas methamphetamine-induced changes were primarily reversible. Functional annotation predicted that approximately 27.5% of these events induce frameshifts, potentially impacting critical microglial pathways such as autophagy (Wdr81), chromatin remodeling (Chd4, Kmt2c), and RNA processing (Hnrnpl, Mbnl2, Tia1). These findings identify previously unrecognized post-transcriptional neuroimmune mechanisms and suggest that persistent splicing dysregulation in microglia may contribute to the long-term pathophysiology of OUD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/716002v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1c30f01org.highwire.dtl.DTLVardef@10e16d7org.highwire.dtl.DTLVardef@1fd80dforg.highwire.dtl.DTLVardef@17c80f_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

Parabrachial CGRP Neurons Regulate Opioid Reinforcement

Opioid use disorder (OUD) is a chronic, relapsing disease driven by the reinforcing properties of opioids and perpetuated by avoidance of the negative affective states associated with the absence of the drug. Most available OUD treatments directly engage the {micro}-opioid receptor and may induce side effects that can compromise their therapeutic efficacy, thus underscoring the need for novel therapeutic alternatives. Calcitonin gene-related peptide (CGRP) is produced by a small population of neurons in the parabrachial nucleus (PBN) that has been shown to modulate itch, pain, as well as appetitive behaviors. Using a cell-specific nuclear labeling approach coupled with RNA-sequencing, we generated a baseline transcriptome of CGRPPBN neurons and confirmed expression of multiple genes associated with behavioral responses to appetitive stimuli, as well as enrichment of the {micro}-opioid receptor, suggesting that CGRPPBN neuron function may be sensitive to the presence of opioids. Indeed, cFos immunostaining showed that CGRPPBN neuron activity increases during early morphine abstinence and reduces gradually over 48 hours. Given the inhibitory effects of opioids on CGRPPBN neuron activity, we next tested whether these neurons could regulate opioid reinforcement. Using a mouse model of morphine intravenous self-administration, we found that chemogenetic inhibition of CGRPPBN neurons significantly reduced the number of morphine rewards earned in both single-dose and dose-response tests but did not affect context-induced morphine seeking after 21 days of abstinence. These results suggest that CGRPPBN neurons are sensitive to opioid administration and can regulate appetitive behaviors such as morphine-taking. Considering that CGRP signaling is regulated by opioid administration, molecular targets that regulate CGRP neurotransmission without direct -opioid receptor engagement may therefore serve as novel therapeutic avenues for the treatment of OUD. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=195 SRC="FIGDIR/small/712659v1_ufig1.gif" ALT="Figure 1"> View larger version (56K): org.highwire.dtl.DTLVardef@1fb9c9borg.highwire.dtl.DTLVardef@1e6ba79org.highwire.dtl.DTLVardef@dc60f5org.highwire.dtl.DTLVardef@61adaf_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

Cocaine taking and craving produce distinct transcriptional profiles in dopamine neurons

Dopamine (DA) signaling plays an essential role in reward valence attribution and in encoding the reinforcing properties of natural and artificial rewards. The adaptive responses from midbrain dopamine neurons to artificial rewards such as drugs of abuse are therefore important for understanding the development of substance use disorders. Drug-induced changes in gene expression are one such adaptation that can determine the activity of dopamine signaling in projection regions of the brain reward system. One of the major challenges to obtaining this understanding involves the complex cellular makeup of the brain, where each neuron population can be defined by a distinct transcriptional profile. To bridge this gap, we have adapted a virus-based method for labeling and capture of dopamine nuclei, coupled with nuclear RNA-sequencing, to study the transcriptional adaptations, specifically, of dopamine neurons in the ventral tegmental area (VTA) during cocaine taking and cocaine craving, using a mouse model of cocaine intravenous self-administration (IVSA). Our results show significant changes in gene expression across non-drug operant training, cocaine taking, and cocaine craving, highlighted by an enrichment of repressive epigenetic modifying enzyme gene expression during cocaine craving. Immunohistochemical validation further revealed an increase of H3K9me3 deposition in DA neurons during cocaine craving. These results demonstrate that cocaine-induced transcriptional adaptations in dopamine neurons vary by phase of self-administration and underscore the utility of this approach for identifying relevant phase-specific molecular targets to study the behavioral course of substance use disorders.

neuroscience↗

bioRxiv2024

Epigenetic heterogeneity shapes the transcriptional landscape of regional microglia

Microglia, the innate immune cells in the central nervous system, exhibit distinct transcriptional profiles across brain regions that are important for facilitating their specialized function. There has been recent interest in identifying the epigenetic modifications associated with these distinct transcriptional profiles, as these may improve our understanding of the underlying mechanisms governing the functional specialization of microglia. One obstacle to achieving this goal is the large number of microglia required to obtain a genome-wide profile for a single histone modification. Given the cellular and regional heterogeneity of the brain, this would require pooling many samples which would impede biological applications that are limited by numbers of available animals. To overcome this obstacle, we have adapted a method of chromatin profiling known as Cleavage Under Targets and Tagmentation (CUT&Tag-Direct) to profile histone modifications associated with regional differences in gene expression throughout the brain reward system. Consistent with previous studies, we find that transcriptional profiles of microglia vary by brain region. However, here we report that these regional differences also exhibit transcriptional network signatures specific to each region. Additionally, we find that these region-dependent network signatures are associated with differential deposition of H3K27ac and H3K7me3, and while the H3K27me3 landscape is remarkably stable across brain regions, the H3K27ac landscape is most consistent with the anatomical location of microglia which explain their distinct transcriptional profiles. Altogether, these findings underscore the established role of H3K27me3 in cell fate determination and support the active role of H3K27ac in the dynamic regulation of microglial gene expression. In this study, we report a molecular and computational framework that can be applied to improve our understanding of the role of epigenetic regulation in microglia in both health and disease, using as few as 2,500 cells per histone mark. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=179 SRC="FIGDIR/small/607229v1_fig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@426944org.highwire.dtl.DTLVardef@d1b9aorg.highwire.dtl.DTLVardef@8f2cedorg.highwire.dtl.DTLVardef@1ce8105_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 1.C_FLOATNO Pipeline of tissue processing and data analysis for the characterization of the microglial transcriptome and epigenome on a regional scale. C_FIG

genetics↗

bioRxiv2023

Microglia contribute to methamphetamine reinforcement and reflect persistent transcriptional and morphological adaptations to the drug

Methamphetamine use disorder (MUD) is a chronic, relapsing disease that is characterized by repeated drug use despite negative consequences and for which there are currently no FDA-approved cessation therapeutics. Repeated methamphetamine (METH) use induces long-term gene expression changes in brain regions associated with reward processing and drug-seeking behavior, and recent evidence suggests that methamphetamine-induced neuroinflammation may also shape behavioral and molecular responses to the drug. Microglia, the resident immune cells in the brain, are principal drivers of neuroinflammatory responses and contribute to the pathophysiology of substance use disorders. Here, we investigated transcriptional and morphological changes in dorsal striatal microglia in response to methamphetamine-taking and during methamphetamine abstinence, as well as their functional contribution to drug-taking behavior. We show that methamphetamine self-administration induces transcriptional changes associated with protein folding, mRNA processing, immune signaling, and neurotransmission in dorsal striatal microglia. Importantly, many of these transcriptional changes persist through abstinence, a finding supported by morphological analyses. Functionally, we report that microglial ablation increases methamphetamine-taking, possibly involving neuroimmune and neurotransmitter regulation, and that post-methamphetamine microglial repopulation attenuates drug-seeking following a 21-day period of abstinence. In contrast, microglial depletion during abstinence did not alter methamphetamine-seeking. Taken together, these results suggest that methamphetamine induces both short and long-term changes in dorsal striatal microglia that contribute to altered drug-taking behavior and may provide valuable insights into the pathophysiology of MUD. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=191 SRC="FIGDIR/small/563168v2_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@640bf6org.highwire.dtl.DTLVardef@4d5f5forg.highwire.dtl.DTLVardef@1b08864org.highwire.dtl.DTLVardef@ca80fa_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗