Neuronal temperature perception induces specific defenses that enable C. elegans to cope with the enhanced reactivity of hydrogen peroxide at high temperature

CaMK modulates sensory neural activity to control longevity and proteostasis

The impact of neural activity on aging and longevity remains poorly understood, with limited understanding of the specific neuron groups and molecular mechanisms that regulate lifespan. In this study, we uncover a correlation between human longevity and reduced CaMK4 expression in the frontal cortex. We further show that this link is conserved in Caenorhabditis elegans, where the loss of the homolog CMK-1 leads to increased longevity and enhanced proteostasis. These beneficial effects are primarily driven by suppressed excitation in the primary thermosensory AFD neurons, particularly at elevated temperatures that trigger hyperactivation. In the thermosensory neural circuit, suppression of AFD neuron activity promotes the release of INS-1/insulin from AIZ, which in turn activates DAF-16/FOXO in the intestine. Our findings reveal a causal mechanism through which sensory neural activity governs lifespan and organismal proteostasis, highlighting the significance of CaMK in shaping these processes through the regulation of neural activity.

Behavioral Cooperation or Conflict of Human Intestinal Roundworms and Microbiomes: A Bio-Activity Perspective

Human infections are greatly impacted by intestinal nematodes. These nematodes, which encompass the large roundworms, have a direct impact on human health and well-being due to their close cohabitation with the host's microorganisms. When nematodes infect a host, the microbiome composition changes, and this can impact the host's ability to control the parasites. We aimed to find out if the small intestinal roundworms produce substances that have antimicrobial properties and respond to their microbial environment, and if the immune and regulatory reactions to nematodes are altered in humans lacking gut microbes. There is no doubt that different nematodes living in the intestines can alter the balance of intestinal bacteria. Nonetheless, our knowledge about the parasite's influence on the gut microbiome remains restricted. The last two decades of study have revealed that the type of iron utilized can influence the activation of unique virulence factors. However, some roundworm proteins like P43, which makes up a large portion of the worm's excretory-secretory product, have an unknown role. This review explores how the bacterial iron regulatory network contributes to the adaptability of this opportunistic pathogen, allowing it to successfully infect nematodes in different host environments.

The AFD-expressed SRTX-1 GPCR does not contribute to AFD thermosensory functions

Temperature experience-regulated gene expression changes have been shown to underlie long-term adaptation of the response threshold of the AFD thermosensory neuron pair, and contribute to thermotaxis behavioral plasticity in C. elegans . We previously showed that the SRTX-1 GPCR is expressed primarily in AFD and is localized to their sensory endings. Here we find that SRTX-1 levels are regulated by the animal's temperature experience. However, loss or overexpression of srtx-1 does not affect thermotaxis behaviors or examined temperature-evoked calcium responses in AFD. Our observations suggest that SRTX-1 may modulate AFD responses and behavior under defined temperature conditions, or in response to specific environmental stimuli.

Polylactic acid microplastics cause transgenerational reproductive toxicity associated with activation of insulin and hedgehog ligands in C. elegans

As a member of biodegradable plastics, exposure risk of polylactic acid microplastic (PLA-MP) has received attention recently. Toxicity of PLA-MP at parental generation (P0-G) has been observed in some organisms; however, its possible transgenerational toxicity and underlying mechanisms remain unclear. In Caenorhabditis elegans, 10 and 100 μg/L PLA-MP resulted in transgenerational inhibition in reproductive capacity and transgenerational damage on gonad development. Meanwhile, transgenerational increase in germline apoptosis was detected after PLA-MP exposure at P0-G, which was associated with transgenerational dysregulation in expressions of genes governing apoptosis (ced-3, ced-4, egl-1, and ced-9) and DNA damage related genes (cep-1, mrt-2, hus-1, and clk-2). Among secreted ligand genes, PLA-MP exposure induced transgenerational increase in expression of ins-39 and wrt-3, and RNAi of ins-39 and wrt-3 inhibited germline apoptosis in PLA-MP exposed nematodes. Additionally, PLA-MP caused transgenerational increase in expression of met-2 and set-6 encoding histone methylation transferases, and germline apoptosis induced by PLA-MP could be suppressed by RNAi of met-2 and set-6. Dysregulated expressions of some apoptosis and DNA damage related genes caused by PLA-MP were reversed by RNAi of ins-39, wrt-3, met-2, and set-6. Moreover, in PLA-MP exposed animals, expression of ins-39 and wrt-3 could be further inhibited by RNAi of met-2 and set-6. Therefore, PLA-MP potentially induced reproductive toxicity across multiple generations, which was under the control of MET-2 and SET-6 activated ligands of INS-39 and WRT-3.

Nanoplastic at environmentally relevant concentrations induces toxicity across multiple generations associated with inhibition in germline G protein-coupled receptor CED-1 in Caenorhabditis elegans

Nanoplastics at environmentally relevant concentrations (ERCs) could cause transgenerational toxicity on organisms. Caenorhabditis elegans is an important model for the study of transgenerational toxicology of pollutants. Nevertheless, the underlying mechanisms for the control of transgenerational nanoplastic toxicity by germline signals remain largely unclear. In C. elegans, exposure to 1-100 μg/L polystyrene nanoparticle (PS-NP) decreased expression of germline ced-1 encoding a G protein-coupled receptor at parental generation (P0-G). After PS-NP exposure at P0-G, transgenerational decrease in germline ced-1 expression could be detected. Meanwhile, the susceptibility to transgenerational PS-NP toxicity was observed in ced-1(RNAi) animals. After PS-NP exposure at P0-G, germline RNAi of ced-1 increased expressions of met-2 and set-6 encoding histone methylation transferases. The susceptibility of ced-1(RNAi) to transgenerational PS-NP toxicity could be inhibited by RNAi of met-2 and set-6. Moreover, in PS-NP exposed met-2(RNAi) and set-6(RNAi) nematodes, expressions of ins-39, wrt-3, and/or efn-3 encoding secreted ligands were decreased. Therefore, our results demonstrated that inhibition in germline CED-1 mediated the toxicity induction of nanoplastics at ERCs across multiple generations in nematodes.

Defining the contribution of microRNA-specific Argonautes with slicer capability in animals

microRNAs regulate gene expression through interaction with an Argonaute protein. While some members of this protein family retain an enzymatic activity capable of cleaving RNA molecules complementary to Argonaute-bound small RNAs, the role of the slicer residues in the canonical microRNA pathway is still unclear in animals. To address this, we created Caenorhabditis elegans strains with mutated slicer residues in the endogenous ALG-1 and ALG-2, the only two slicing Argonautes essential for the miRNA pathway in this animal model. We observe that the mutation in ALG-1 and ALG-2 catalytic residues affects overall animal fitness and causes phenotypes reminiscent of miRNA defects only when grown and maintained at restrictive temperature. Furthermore, the analysis of global miRNA expression shows that the slicer residues of ALG-1 and ALG-2 contribute differentially to regulate the level of specific subsets of miRNAs in young adults. We also demonstrate that altering the catalytic tetrad of those miRNA-specific Argonautes does not result in any defect in the production of canonical miRNAs. Together, these data support that the slicer residues of miRNA-specific Argonautes contribute to maintaining levels of a set of miRNAs for optimal viability and fitness in animals particularly exposed to specific growing conditions.

Sex-specific developmental gene expression atlas unveils dimorphic gene networks in C. elegans

Sex-specific traits and behaviors emerge during development by the acquisition of unique properties in the nervous system of each sex. However, the genetic events responsible for introducing these sex-specific features remain poorly understood. In this study, we create a comprehensive gene expression atlas of pure populations of hermaphrodites and males of the nematode Caenorhabditis elegans across development. We discover numerous differentially expressed genes, including neuronal gene families like transcription factors, neuropeptides, and G protein-coupled receptors. We identify INS-39, an insulin-like peptide, as a prominent male-biased gene expressed specifically in ciliated sensory neurons. We show that INS-39 serves as an early-stage male marker, facilitating the effective isolation of males in high-throughput experiments. Through complex and sex-specific regulation, ins-39 plays pleiotropic sexually dimorphic roles in various behaviors, while also playing a shared, dimorphic role in early life stress. This study offers a comparative sexual and developmental gene expression database for C. elegans. Furthermore, it highlights conserved genes that may underlie the sexually dimorphic manifestation of different human diseases.

Defining the contribution of microRNA-specific slicing Argonautes in animals

microRNAs regulate gene expression through interaction with an Argonaute protein family member. While some members of this protein family retain an enzymatic activity capable of cleaving RNA molecules complementary to Argonaute-bound small RNAs, the role of the slicing activity in the canonical microRNA pathway is still unclear in animals. To address the importance of slicing Argonautes in animals, we created Caenorhabditis elegans strains, carrying catalytically dead endogenous ALG-1 and ALG-2, the only two slicing Argonautes essential for the miRNA pathway in this animal model. We observe that the loss of ALG-1 and ALG-2 slicing activity affects overall animal fitness and causes phenotypes, reminiscent of miRNA defects, only when grown and maintained at restrictive temperature. Furthermore, the analysis of global miRNA expression shows that the catalytic activity of ALG-1 and ALG-2 differentially regulate the level of specific subsets of miRNAs in young adults. We also demonstrate that altering the slicing activity of those miRNA-specific Argonautes does not result in any defect in the production of canonical miRNAs. Together, these data support that the slicing activity of miRNA-specific Argonautes function to maintain the levels of a set of miRNAs for optimal viability and fitness in animals particularly exposed to specific growing conditions.

Molecular encoding of stimulus features in a single sensory neuron type enables neuronal and behavioral plasticity

Neurons modify their transcriptomes in response to an animal's experience. How specific experiences are transduced to modulate gene expression and precisely tune neuronal functions are not fully defined. Here, we describe the molecular profile of a thermosensory neuron pair in C. elegans experiencing different temperature stimuli. We find that distinct salient features of the temperature stimulus, including its duration, magnitude of change, and absolute value, are encoded in the gene expression program in this single neuron type, and we identify a novel transmembrane protein and a transcription factor whose specific transcriptional dynamics are essential to drive neuronal, behavioral, and developmental plasticity. Expression changes are driven by broadly expressed activity-dependent transcription factors and corresponding cis-regulatory elements that nevertheless direct neuron- and stimulus-specific gene expression programs. Our results indicate that coupling of defined stimulus characteristics to the gene regulatory logic in individual specialized neuron types can customize neuronal properties to drive precise behavioral adaptation.

Molecular encoding of stimulus features in a single sensory neuron type enables neuronal and behavioral plasticity

Neurons modify their transcriptomes in response to an animal’s experience. How specific experiences are transduced to modulate gene expression and precisely tune neuronal functions are not fully defined. Here, we describe the molecular profile of a thermosensory neuron pair in C. elegans experiencing different temperature stimuli. We find that distinct salient features of the temperature stimulus including its duration, magnitude of change, and absolute value are encoded in the gene expression program in this single neuron, and identify a novel transmembrane protein and a transcription factor whose specific transcriptional dynamics are essential to drive neuronal, behavioral, and developmental plasticity. Expression changes are driven by broadly expressed activity-dependent transcription factors and corresponding cis -regulatory elements that nevertheless direct neuron- and stimulus-specific gene expression programs. Our results indicate that coupling of defined stimulus characteristics to the gene regulatory logic in individual specialized neuron types can customize neuronal properties to drive precise behavioral adaptation.

Neuronal temperature perception induces specific defenses that enable C. elegans to cope with the enhanced reactivity of hydrogen peroxide at high temperature

Hydrogen peroxide is the most common reactive chemical that organisms face on the microbial battlefield. The rate with which hydrogen peroxide damages biomolecules required for life increases with temperature, yet little is known about how organisms cope with this temperature-dependent threat. Here, we show that Caenorhabditis elegans nematodes use temperature information perceived by sensory neurons to cope with the temperature-dependent threat of hydrogen peroxide produced by the pathogenic bacterium Enterococcus faecium. These nematodes preemptively induce the expression of specific hydrogen peroxide defenses in response to perception of high temperature by a pair of sensory neurons. These neurons communicate temperature information to target tissues expressing those defenses via an insulin/IGF1 hormone. This is the first example of a multicellular organism inducing their defenses to a chemical when they sense an inherent enhancer of the reactivity of that chemical.