Biology subjects

Salter, M. W.

Publications and source records attributed to Salter, M. W..

10 recordsLinked to original sources

bioRxiv2026

TRACR: an anterograde transneuronal tracing system for genetic access across synapses and longitudinal circuit analysis

Following neural signals as they converge onto and diverge from individual neurons is central to understanding circuit function and disease-related dysfunction. Existing anterograde transneuronal tracers are limited by cytotoxicity and incomplete genetic control over connected partners. To address these limitations, we adapted synthetic Notch designs to create TRanssynaptic Anterograde Circuit Readout (TRACR). Binding of the engineered ligand-receptor across synapses induces TRE-driven reporter transcription, enabling characterization of postsynaptic neurons. TRACR provides segregated genetic access to pre- and postsynaptic populations, and can be combined with markers, sensors, or effectors to expand circuit analysis. By applying TRACR at multiple synapses in the mouse visual system, we show that TRACR labels postsynaptic partners of sensory neurons, long-range projections and local inhibitory interneurons. TRACR signaling is reversible and fails to activate when synapses are absent or disrupted. Together, TRACR is an accessible, AAV-deliverable transneuronal reporting tool for longitudinal analysis of circuit assembly, degeneration, and repair. HIGHLIGHTSO_LITRACR adapts the synNotch system to signal across synapses for tracing postsynaptic targets. C_LIO_LITRACR identifies local and long-range postsynaptic targets in the mouse visual system. C_LIO_LITRACR activation requires intact synaptic connectivity rather than proximity. C_LIO_LITRACR signals are reversible, diminishing upon synapse loss and activating following assembly. C_LI

neuroscience↗

bioRxiv2025

Meningeal macrophages mask incision pain sensitization in male rats

IntroductionMeninges surrounding the brain and spinal cord house a variety of immune cell types including macrophages that express the CD206 mannose receptor. Here, we investigated whether CD206+ macrophages in the meninges play a role in regulating nociception and pain hypersensitivity. MethodsWe selectively depleted CD206+ macrophages in the meninges around the lumbar spinal cord by intrathecal administration of anti-CD206 coupled to saporin, and determined the effects of CD206+ macrophage depletion on responses in naive rats and in those that had received a skin incision to the upper hindlimb. In addition, we used RNAseq to investigate transcriptional changes in lumbar meninges and dorsal root ganglia. Experiments were done in both male and female rats. ResultsDepleting CD206+ meningeal macrophages did not alter basal responses in naive animals of either sex. By contrast depleting these cells after skin injury induced mechanical hypersensitivity in male rats, without changes in thermal sensitivity but had no effect in females. In male rats with skin incision injury, we found that the mechanical hypersensitivity induced by depleting CD206+ meningeal macrophages was reversed by administering the NMDAR antagonist, APV. In addition, the hypersensitivity was reversed by an enhancer of KCC2 function, CLP290. Unexpectedly, skin incision caused significant transcriptional changes in the meninges, but only in male rats. ConclusionsTaken together, our results indicate that while CD206+ meningeal macrophages do not regulate basal nociception in naive rats, after skin incision injury, these cells mask mechanical hypersensitivity in male rats only. Thus, we conclude that in a sex-dependent manner CD206+ meningeal macrophages prevent the spread of pain hypersensitivity after a minor injury. Importantly, the skin incision we used was comparable to that used in sham controls in numerous rodent studies of neuropathic pain. Our findings have, therefore, potentially broad implications for re-interpreting results from previous neuropathic pain research.

neuroscience↗

bioRxiv2024

Blocking Src-PSD-95 interaction rescues glutamatergic signaling dysregulation in schizophrenia.

The complex and heterogeneous genetic architecture of schizophrenia inspires us to look beyond individual risk genes for therapeutic strategies and target their interactive dynamics and convergence. Postsynaptic NMDA receptor (NMDAR) complexes are a site of such convergence. Src kinase is a molecular hub of NMDAR function, and its protein interaction subnetwork is enriched for risk-genes and altered protein associations in schizophrenia. Previously, Src activity was found to be decreased in post-mortem studies of schizophrenia, contributing to NMDAR hypofunction. PSD-95 suppresses Src via interacting with its SH2 domain. Here, we devised a strategy to suppress the inhibition of Src by PSD-95 via employing a cell penetrating and Src activating PSD-95 inhibitory peptide (TAT-SAPIP). TAT-SAPIP selectively increased post-synaptic Src activity in humans and mice, and enhanced synaptic NMDAR currents in mice. Chronic ICV injection of TAT-SAPIP rescued deficits in trace fear conditioning in Src hypomorphic mice. We propose blockade of the Src-PSD-95 interaction as a proof of concept for the use of interfering peptides as a therapeutic strategy to reverse NMDAR hypofunction in schizophrenia and other illnesses.

neuroscience↗

bioRxiv2023

Hyperexcitability in human MECP2 null neuronal networks manifests as calcium-dependent reverberating super bursts

Rett syndrome (RTT) patients show abnormal developmental trajectories including loss of language and repetitive hand movements but also have signs of cortical hyperexcitability such as seizures. RTT is predominantly caused by mutations in MECP2 and can be modelled in vitro using human stem cell-derived neurons. MECP2 null excitatory neurons are smaller in soma size and have reduced synaptic connectivity but are also hyperexcitable, due to higher input resistance, which increases the chance to evoke action potentials with a given depolarized current. Few studies examine how single neuron activity integrates into neuronal networks during human development. Paradoxically, networks of MECP2 null neurons show a decrease in the frequency of bursting patterns consistent with synaptic hypoconnectivity, but no hyperexcitable network events have been reported. Here, we show that MECP2 null neurons have an increase in the frequency of a network event described as reverberating super bursts (RSBs) relative to isogenic controls. RSBs can be mistakenly called as a single long duration burst by standard burst detection algorithms. However, close examination revealed an initial large amplitude network burst followed by high frequency repetitive low amplitude mini-bursts. Using a custom burst detection algorithm, we unfolded the multi-burst structure of RSBs revealing that MECP2 null networks increased the total number of bursts relative to isogenic controls. Application of the Ca2+ chelator EGTA-AM selectively eliminated RSBs and rescued the network burst phenotype relative to the isogenic controls. Our results indicate that during early development, MECP2 null neurons are hyperexcitable and produce hyperexcitable networks. This may predispose them to the emergence of hyper-synchronic states that potentially translate into seizures. Network hyperexcitability is dependent on asynchronous neurotransmitter release driven by pre-synaptic Ca2+ and can be rescued by EGTA-AM to restore typical network dynamics. HIGHLIGHTSO_LIReverberating super-bursts (RSBs) follow a stereotypic form of a large initial network burst followed by several smaller amplitude high-frequency mini-bursts. C_LIO_LIRSBs occur more often in MECP2 null excitatory networks. C_LIO_LIMECP2 null excitatory networks with increased RSBs show a hyperexcitable network burst phenotype relative to isogenic controls. C_LIO_LIThe calcium chelator, EGTA-AM, decreases RSBs and rescues the dynamics of MECP2 null hyperexcitable networks. C_LI

neuroscience↗

bioRxiv2023

Pain hypersensitivity is dependent on autophagy protein Beclin 1 in males but not females

Chronic pain is a pervasive health, social, and economic problem affecting 1 in 5 individuals around the world. Increasingly, it is understood that alterations in fundamental cell biological processes are critical for chronic pain. A prominent cellular process is autophagy but whether it plays a role in pain is unknown. To investigate whether autophagy is involved in pain processing and is targetable for pain relief, we focused on Beclin 1, a component of the class III phosphatidylinositol 3-kinase (PI3K) complex necessary for initiating autophagy. Here, we found that inflammatory pain hypersensitivity in male mice lacking one allele of Becn1 is significantly greater than that in wild type mice. By contrast, in female mice, loss of Becn1 did not affect inflammation-induced pain hypersensitivity. Further, intrathecal delivery of an activator of Beclin 1, tat-beclin 1, reversed mechanical hypersensitivity induced by peripheral inflammation or peripheral nerve injury in males. Tat-beclin 1 also prevented mechanical hypersensitivity induced by exogenous brain-derived neurotrophic factor (BDNF), a core mediator of inflammatory and neuropathic pain in the spinal dorsal horn in males. Pain signaling pathways converge on enhancement of N-methyl-D-aspartate receptors (NMDARs) in spinal dorsal horn neurons. We found that loss of Beclin 1 increases expression of the pain-critical NMDAR subunit, GluN2B, in the dorsal horn and upregulates synaptic NMDAR-mediated currents in dorsal horn neurons from males but not females. From our converging lines of evidence, we conclude that inhibition of Beclin 1 in the dorsal horn is critical in mediating inflammatory and neuropathic pain signaling pathways in males. Our findings provide the basis for sex-specific therapeutic approaches targeting pain with a new class of analgesics - activators of Beclin 1.

neuroscience↗

bioRxiv2023

A Cas9-fusion proximity-based approach generates an Irak1-Mecp2 tandem duplication mouse model for the study of MeCP2 duplication syndrome.

MECP2 duplication syndrome (MDS) is a neurodevelopmental disorder caused by tandem duplication of the MECP2 locus and its surrounding genes, including IRAK1. Current MDS mouse models involve transgenic expression of MECP2 only, limiting their applicability to the study of the disease. Herein, we show that an efficient and precise CRISPR/Cas9 fusion proximity-based approach can be utilized to generate an Irak1-Mecp2 tandem duplication mouse model. The Mecp2 Dup model displays a neurological phenotype in keeping with MDS and demonstrates an abnormal immune response to infection not previously observed in other mouse models, possibly stemming from concurrent Irak1 overexpression. The Mecp2 Dup mouse line thus provides an innovative tool to investigate disease mechanisms and potential therapeutic development.

genetics↗

bioRxiv2022

Regulation of neuropathic pain by microglial Orai1 channels

Microglia are important mediators of neuroinflammation that underlies neuropathic pain. However, the molecular checkpoints controlling microglial reactivity are not well-understood. We investigated the role of Orai1 channels for microglia-mediated neuroinflammation following nerve injury and find that deletion of Orai1 in microglia attenuates Ca2+ signaling and the production of inflammatory cytokines by proalgesic agonists. Conditional deletion of Orai1 attenuated microglia proliferation in the dorsal horn, spinal cytokines levels, and potentiation of excitatory neurotransmission following peripheral nerve injury. These cellular effects were accompanied by mitigation of pain hyperalgesia in Orai1 knockout mice. A small-molecule Orai1 inhibitor, CM4620, similarly mitigated allodynia in male mice. Surprisingly, these protective effects were not seen in female mice, revealing striking sexual dimorphism in Orai1 regulation of microglial reactivity and hyperalgesia. These findings indicate that Orai1 channels are key regulators of the sexually dimorphic role of microglia for the neuroinflammation that underlies neuropathic pain.

neuroscience↗

bioRxiv2022

Conserved transcriptional programming across sex and species after peripheral nerve injury predicts treatments for neuropathic pain

Chronic pain is a devastating problem affecting 1 in 5 individuals around the globe, with neuropathic pain the most debilitating and poorly treated type of chronic pain. Advances in transcriptomics and data mining have contributed to cataloging diverse cellular pathways and transcriptomic alterations in response to peripheral nerve injury but have focused on phenomenology and classifying transcriptomic responses. Here, with the goal of identifying new types of pain-relieving agents, we compared transcriptional reprogramming changes in the dorsal spinal cord after peripheral nerve injury cross-sex and cross-species and imputed commonalities, as well as differences in cellular pathways and gene regulation. We identified 93 transcripts in the dorsal horn that were increased by peripheral nerve injury in male and female mice and rats. Following gene ontology and transcription factor analyses, we constructed a pain interactome for the proteins encoded by the differentially expressed genes, discovering new, conserved signaling nodes. We interrogated the interactome with the Drug-Gene database to predict FDA-approved medications that may modulate key nodes within the network. The top hit from the analysis was fostamatinib, the molecular target of which is the non-receptor tyrosine kinase Syk, which our analysis had identified as a key node in the interactome. We found that intrathecally administrating the active metabolite of fostamatinib, R406, significantly reversed pain hypersensitivity in both sexes. Thus, we have identified and shown the efficacy of an agent that could not have been previously predicted to have analgesic properties. One sentence summaryUnbiased approach to predicting safe therapies for neuropathic pain

neuroscience↗

bioRxiv2022

Methacrylic acid-based biomaterials promote peripheral innervation in the subcutaneous space of mice

Peripheral nerve innervation is essential for regulating tissue repair and regeneration. MAA-based biomaterials have been previously shown to promote angiogenesis. Here we show a new role for MAA-based biomaterials in promoting terminal axon nerve growth. Our results demonstrate that MAA-based biomaterials promote peripheral nerve growth in an Igf-1 and Shh dependent manner. The resulting nerves increased the sensitivity of treated mice paws to nociception. iDISCO clearing showed that MAA increased the presence of peripheral nerve structures in whole explants. MAA was also able to increase the expression of key neuronal markers and growth factors in a peripheral neuropathy model, the diabetic db/db mouse, suggesting that MAA-based biomaterials may be relevant to treatment of peripheral neuropathy. Moreover, in a peripheral neuropathy model, MAA was able to up-regulate the expression of growth factors for an extended duration suggesting MAA may prevent degeneration through an effect on factors that promote survival. As all tissues are innervated, MAA-based biomaterials could have broad applications in the promoting regeneration and preventing degeneration of peripheral nerves. HIGHLIGHTSO_LIMethacrylic acid-based biomaterials promote axon growth in-situ without exogenous growth factors or cells C_LIO_LIMethacrylic acid-based biomaterial induced terminal axon growth displays nociception, an indicator of functional outgrowth C_LIO_LIMethacrylic acid-based biomaterials terminal axon growth is Igf-1 and Shh driven C_LI

bioengineering↗

bioRxiv2020

Single-cell RNA sequencing reveals time- and sex-specific responses of spinal cord microglia to peripheral nerve injury and links ApoE to neuropathic pain

Activation of microglia in the spinal cord following peripheral nerve injury is critical for the development of long-lasting pain hypersensitivity. However, it remains unknown whether distinct microglia subpopulations or states contribute to different stages of pain development and maintenance. We show, using single-cell RNA-sequencing, that nerve injury induces the generation of a male-specific inflammatory microglia subtype, and demonstrate increased proliferation of microglia in males as compared to females. We also show time- and sex-specific transcriptional changes in different microglial subpopulations following injury. Apolipoprotein E (Apoe) is the top upregulated gene in microglia at chronic time points after nerve injury in mice and polymorphisms in the APOE gene in humans are associated with chronic pain. Single-cell analysis of human spinal cord microglia reveals a subpopulation with a disease-related transcriptional signature. Our data provide a detailed analysis of transcriptional states of mouse and human spinal cord microglia, and identify a previously unrecognized role for ApoE in neuropathic pain.

neuroscience↗