Biology subjects

Valdivia, S.

Publications and source records attributed to Valdivia, S..

6 recordsLinked to original sources

bioRxiv2026

CGRP receptor-expressing neurons in the central amygdala contributes to injury-induced pain hypersensitivity

The central nucleus of amygdala (CeA) comprises diverse populations of neurons, forming a complex network responsible for regulating various behavioral responses. Among these, neurons expressing calcitonin gene-related peptide receptors (CGRPR) have emerged as key players in CGRP neuropeptide-mediated pain modulation. While previous studies emphasize CGRPs key role in synaptic plasticity and its connection with pain behavior in the CeA, the precise functional attributes and contributions of CeA-CGRPR-expressing neurons in pain processing remain elusive. This study reveals the co-localization of CGRPR-expressing neurons in the CeA with phosphorylated extracellular signal-regulated kinase (pERK), a marker indicating pain plasticity, in a neuropathic pain model. Electrophysiological assessments of these neurons in slice preparations unveiled heightened intrinsic excitability after sciatic nerve cuff implantation, contingent upon their rostro-caudal positioning within the CeA. Furthermore, our behavioral experiments using chemogenetic inhibition of CeA-CGRPR neurons demonstrated the ability to reverse nerve injury-induced hypersensitivity. Conversely, activating these neurons induced pain-related hypersensitivity even in the absence of injury. Our findings also highlight a sex-specific role of CeA-CGRPR neurons in formalin-induced spontaneous pain response. Collectively, these data reinforce the involvement of CeA-CGRPR neurons in pain processing, contributing to a better understanding of how neural circuits are affected in persistent pain conditions. Significance StatementOur study shows the role of CGRPR-expressing neurons within the CeA during pain processing. Using a cuff-implanted neuropathic mouse model, we discovered that CGRPR-expressing neurons co-localize with phosphorylated extracellular signal-regulated kinase (pERK), a hallmark of pain plasticity, in both male and female mice. Furthermore, our electrophysiological investigations reveal that posterior CeA-CGRPR neurons exhibit increased excitability following sciatic nerve cuff implantation. Importantly, we demonstrate that CeA-CGRPR neurons exert bidirectional effects on pain behavior in mice, irrespective of sex differences in nerve injury-induced pain responses while showing sex-specific spontaneous pain responses in the formalin-induced model. These findings show the role of CeA-CGRPR neurons in pain modulation, underscoring their potential significance in understanding and addressing persistent pain conditions.

neuroscience↗

bioRxiv2026

Identification of novel inhibitors of Mycobacterium smegmatis growth through genome-wide overexpression of Cluster P3 mycobacteriophage Xavia genes

We examined whether genes encoded by the mycobacteriophage Xavia disrupt growth of Mycobacterium smegmatis, a widely used mycobacterial model. Seventy-one Xavia genes were individually expressed using an inducible plasmid system and assessed for effects on colony formation. Two genes were lethal even without induction, indicating toxicity under basal expression. Induction of sixteen additional genes reduced bacterial growth, spanning structural proteins, lysogeny regulators, DNA-associated enzymes, a lysis protein, and several genes with no known function. These findings expand functional insights into mycobacteriophage gene repertoires and identify candidates for future mechanistic studies. AbstractBacteriophage genomes encode large numbers of genes with no known function, and many of these genes affect essential host processes when expressed in a heterologous system. For mycobacteriophages, genome-wide overexpression in Mycobacterium smegmatis provides a direct way to identify proteins that impair growth and to determine which mycobacterial pathways are sensitive to phage gene products. To evaluate the cytotoxic potential of the Cluster P3 phage Xavia, a lineage that has not undergone functional screening, we constructed an arrayed pExTra library containing 71 predicted Xavia genes under control of the anhydrotetracycline inducible promoter pTet. All constructs were sequence-verified and transformed into M. smegmatis, and induction allowed measurement of gene-specific effects on growth. Two genes prevented recovery of transformants, suggesting toxicity under basal promoter leakiness. Inducible expression of 16 additional genes impaired growth, and these inhibitory proteins include structural components, regulators of lysogeny, enzymes of DNA metabolism, a lysis factor, and several proteins with no known function. Four of the strongest inhibitors were genes with no known function. These results extend functional screening into the previously untested P3 branch of Actinobacteriophages and identify new proteins that require mechanistic analysis.

microbiology↗

bioRxiv2025

Implications of Endogenous Small Regulatory RNAs on Gene Silencing in Mollusks

Mollusks are an abundant group of animals with many economically important members that are phylogenetically distinct from nearly all genetic model organisms. This study provides clade-wide evaluation of sRNA biogenesis pathways, with emphasis on the easter oyster, Crassostrea virginica. Understanding these molecules prescribes RNAi-based gene silencing approaches, benefiting genetic investigation and biotechnology. Similar to other animal groups, mollusks have conserved microRNAs (miRNAs) with some shared with ecdysozoans and deuterostomes; however, there was no evidence of an endogenous small-interfering RNA (siRNA) pathway. These results suggest that long double-stranded RNA (dsRNA)-based RNAi is not appropriate for gene silencing in Mollusks as well as other members of the broader Lophotrochozoan clade. The study also finds an abundance of piwi-interacting RNAs (piRNAs) in both soma and gonads. Differences are also found in piRNA biology. Many invertebrates exhibit somatic piRNAs; however, mollusk piRNAs appear to be restricted to a subset of cells, limiting the potential of piRNA-based RNAi. Further, individual animals also express a unique collection of piRNAs that seem to be only partially determined through inheritance from both parents. Together this work defines the RNAi mechanisms in mollusks, which represent 23% of animals, and provides insights into the phenotypic diversity seen in this group. Significance StatementThis study provides an extensive, clade-wide evaluation of small RNA (sRNA) biogenesis pathways in mollusks. Our findings reveal that, unlike ecdysozoans and deuterostomes, mollusks lack a functional siRNA pathway, which fundamentally changes expectations around RNA interference (RNAi) applications in Mollusca. Instead, we find the expected microRNAs and an assortment of piwi-interacting RNAs (piRNAs). We show that piRNA biology in mollusks is highly cell-type specific and genetically individualized. We further demonstrate that piRNA expression is likely linked to stem-like, quiescent cells, suggesting a critical role in genomic maintenance. This work offers insight into RNAi potential in mollusks, the second largest animal phylum, and has significant implications for both basic biology and applied sciences such as pest control and aquaculture.

evolutionary biology↗

bioRxiv2025

Processing of Genomic RNAs by Dicer in Bat Cells Limits SARS-CoV-2 Replication

Bats are reservoirs for numerous viruses that cause serious diseases in other animals and humans. Several mechanisms are proposed to contribute to the tolerance of bats to these pathogens. This study investigates the response of bat cells to double-stranded RNA generated by SARS-CoV-2 replication. Here, we found the involvement of Dicer in the processing of viral genomic RNAs during SARS-CoV-2 infection. Examining RNA sequencing of infected cells, small-interfering RNA (siRNA)-like fragments were found derived from viral RNAs. Depletion of Dicer showed a reduction in these RNAs and an increase in viral loads suggesting unlike other mammals, bats may use Dicer to limit viral replication. This prompted the exploration of key dsRNA sensors in bat cells. Our analysis showed significant upregulation of OAS1 and MX1 in response to dsRNA, while PKR levels remained low, suggesting alternative dsRNA-response mechanisms are present that eschew the common PKR-based system. These results further show how bats employ distinct strategies for antiviral defense that may contribute to tolerating viral infections. They suggest the involvement of Dicer in antiviral mechanisms in bats, a function not observed in other mammals. This highlights a mechanism for bat originating viruses to evolve features that in other animals could cause extreme antiviral responses such as is seen with SARS-CoV-2. GRAPHICAL SUMMARY O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=152 SRC="FIGDIR/small/632425v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1755d68org.highwire.dtl.DTLVardef@475cb8org.highwire.dtl.DTLVardef@1185813org.highwire.dtl.DTLVardef@13e847a_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2021

Bidirectional modulation of pain-related behaviors in the zona incerta

Central amygdala neurons expressing protein kinase C-delta (CeA-PKC{delta}) are sensitized following nerve injury and promote pain-related responses in mice. The neural circuits underlying modulation of pain-related behaviors by CeA-PKC{delta} neurons, however, remain unknown. In this study, we identified a functional monosynaptic inhibitory neural circuit that originates in CeA-PKC{delta} neurons and terminates in the ventral region of the zona incerta (ZI), a subthalamic structure previously linked to pain processing. Behavioral experiments further show that chemogenetic inhibition of GABAergic ZI neurons is sufficient to induce bilateral hypersensitivity in uninjured mice as well as contralateral hypersensitivity after nerve injury. In contrast, chemogenetic activation of GABAergic ZI neurons reverses nerve injury-induced hypersensitivity, demonstrating that silencing of the ZI is required for injury-induced behavioral hypersensitivity. Our results identify a previously unrecognized inhibitory efferent pathway from CeA-PKC{delta} neurons to the ZI and demonstrate that ZI-GABAergic neurons can bidirectionally modulate pain-related behaviors in mice.

neuroscience↗

bioRxiv2019

Cell-type specificity of neuronal excitability and morphology in the central amygdala

Central amygdala (CeA) neurons expressing protein kinase C delta (PKC{delta}+) or Somatostatin (Som+) differentially modulate diverse behaviors. The underlying features supporting cell-type-specific function in the CeA, however, remain unknown. Using whole-cell patch-clamp electrophysiology in acute mouse brain slices and biocytin-based neuronal reconstructions, we demonstrate that neuronal morphology and relative excitability are two distinguishing features between Som+ and PKC{delta}+ CeLC neurons. Som+ neurons, for example, are more excitable, compact and with more complex dendritic arborizations than PKC{delta}+ neurons. Cell size, intrinsic membrane properties, and anatomical localization were further shown to correlate with cell-type-specific differences in excitability. Lastly, in the context of neuropathic pain, we show a shift in the excitability equilibrium between PKC{delta}+ and Som+ neurons, suggesting that imbalances in the relative output of these cells underlie maladaptive changes in behaviors. Together, our results identify fundamentally important distinguishing features of PKC{delta}+ and Som+ cells that support cell-type-specific function in the CeA.

neuroscience↗