Isolation, profiling, and tracking of extracellular vesicle cargo in Caenorhabditis elegans

Polycystins recruit cargo to distinct ciliary extracellular vesicle subtypes in C. elegans

Therapeutic use of tiny extracellular vesicles (EVs) requires understanding cargo loading mechanisms. Here, we use a modular proximity labeling approach to identify the cargo of ciliary EVs associated with the transient receptor potential channel polycystin-2 PKD-2 of C. elegans. Polycystins are conserved ciliary proteins and cargo of EVs; dysfunction causes polycystic kidney disease in humans and mating deficits in C. elegans. We discover that polycystins localize with specific cargo on ciliary EVs: polycystin-associated channel-like protein PACL-1, dorsal and ventral polycystin-associated membrane C-type lectins PAMLs, and conserved tumor necrosis factor receptor-associated factor (TRAF) TRF-1 and TRF-2. Loading of these components to EVs relies on polycystin-1 LOV-1. Our modular EV-TurboID approach can be applied in both cell- and tissue-specific manners to define the composition of distinct EV subtypes, addressing a major challenge of the EV field.

Mitochondrial Protein MjEF-Tu is Secreted into Host Plants by Nematodes Eliciting Immune Signaling and Resistance

Little is known about plant-parasitic animal-derived pathogen-associated molecular pattern (PAMP)/ pattern-recognition receptor (PRR) pairs. Additionally, mitochondrial proteins have not previously been reported to be secreted into hosts by pathogens. Here, it is found that the Meloidogyne javanica elongation factor thermo unstable (EF-Tu) (MjEF-Tu) located in the nematode mitochondria is up-regulated and secreted into the host plant during nematode parasitism. MjEF-Tu interacts with the PRR Arabidopsis thaliana EF-Tu receptor (AtEFR), triggering the plant hallmark defence responses mediated by AtEFR. An 18-aa sequence (Nelf18) in the N terminus of the nematode EF-Tu contributes to the immunogenic activity. M. javanica water extract and mitochondrial extract also induce plant immunity sensed by AtEFR, owing to the presence of MjEF-Tu. In addition, Nelf18 enhances plant resistance to nematode, virus, and bacterial infections depending on AtEFR. These findings first demonstrate that mitochondrial proteins from pathogens can be secreted into hosts and function as a cross-kingdom signal and identified the first plant-parasitic animal-derived proteinaceous PAMP/PRR pair, providing novel insights into host-pathogen interactions.

The abundance change of age-regulated secreted proteins affects lifespan of C. elegans

Proteome integrity is vital for survival and failure to maintain it results in uncontrolled protein abundances, misfolding and aggregation which cause proteotoxicity. In multicellular organisms, proteotoxic stress is communicated among tissues to maintain proteome integrity for organismal stress resistance and survival. However, the nature of these signalling molecules and their regulation in extracellular space is largely unknown. Secreted proteins are induced in response to various stresses and aging, indicating their roles in inter-tissue communication. To study the fates of age-regulated proteins with potential localization to extracellular, we analysed publicly available age-related proteome data of C. elegans. We found that abundance of majority of the proteins with signal peptides (SP) increases with age, which might result in their supersaturation and subsequent aggregation. Intriguingly, these changes are differentially regulated in the lifespan mutants. A subset of these SP proteins is also found in the cargo of extracellular vesicles. Many of these proteins are novel and functionally uncharacterized. Reducing levels of a few extracellular proteins results in increasing lifespan. This suggests that uncontrolled levels of extracellular proteins might disturb proteostasis and limit the lifespan. Overall, our findings suggest that the age-induced secreted proteins might be the potential candidates to be considered as biomarkers or for mitigating age-related pathological conditions.

SID-2 is a conserved extracellular vesicle protein that is not associated with environmental RNAi in parasitic nematodes

In the free-living nematode Caenorhabditis elegans, the transmembrane protein SID-2 imports double-stranded RNA into intestinal cells to trigger systemic RNA interference (RNAi), allowing organisms to sense and respond to environmental cues such as the presence of pathogens. This process, known as environmental RNAi, has not been observed in the most closely related parasites that are also within clade V. Previous sequence-based searches failed to identify sid-2 orthologues in available clade V parasite genomes. In this study, we identified sid-2 orthologues in these parasites using genome synteny and protein structure-based comparison, following identification of a SID-2 orthologue in extracellular vesicles from the murine intestinal parasitic nematode Heligmosomoides bakeri. Expression of GFP-tagged H. bakeri SID-2 in C. elegans showed similar localization to the intestinal apical membrane as seen for GFP-tagged C. elegans SID-2, and further showed mobility in intestinal cells in vesicle-like structures. We tested the capacity of H. bakeri SID-2 to functionally complement environmental RNAi in a C. elegans SID-2 null mutant and show that H. bakeri SID-2 does not rescue the phenotype in this context. Our work identifies SID-2 as a highly abundant EV protein whose ancestral function may be unrelated to environmental RNAi, and rather highlights an association with extracellular vesicles in nematodes.

The Caenorhabditis elegans cuticle and precuticle: a model for studying dynamic apical extracellular matrices in vivo

Apical extracellular matrices (aECMs) coat the exposed surfaces of animal bodies to shape tissues, influence social interactions, and protect against pathogens and other environmental challenges. In the nematode Caenorhabditis elegans, collagenous cuticle and zona pellucida protein-rich precuticle aECMs alternately coat external epithelia across the molt cycle and play many important roles in the worm's development, behavior, and physiology. Both these types of aECMs contain many matrix proteins related to those in vertebrates, as well as some that are nematode-specific. Extensive differences observed among tissues and life stages demonstrate that aECMs are a major feature of epithelial cell identity. In addition to forming discrete layers, some cuticle components assemble into complex substructures such as ridges, furrows, and nanoscale pillars. The epidermis and cuticle are mechanically linked, allowing the epidermis to sense cuticle damage and induce protective innate immune and stress responses. The C. elegans model, with its optical transparency, facilitates the study of aECM cell biology and structure/function relationships and all the myriad ways by which aECM can influence an organism.

Extracellular vesicles

Extracellular vesicles (EVs) encompass a diverse array of membrane-bound organelles released outside cells in response to developmental and physiological cell needs. EVs play important roles in remodeling the shape and content of differentiating cells and can rescue damaged cells from toxic or dysfunctional content. EVs can send signals and transfer metabolites between tissues and organisms to regulate development, respond to stress or tissue damage, or alter mating behaviors. While many EV functions have been uncovered by characterizing ex vivo EVs isolated from body fluids and cultured cells, research using the nematode Caenorhabditis elegans has provided insights into the in vivo functions, biogenesis, and uptake pathways. The C. elegans EV field has also developed methods to analyze endogenous EVs within the organismal context of development and adult physiology in free-living, behaving animals. In this review, we summarize major themes that have emerged for C. elegans EVs and their relevance to human health and disease. We also highlight the diversity of biogenesis mechanisms, locations, and functions of worm EVs and discuss open questions and unexplored topics tenable in C. elegans, given the nematode model is ideal for light and electron microscopy, genetic screens, genome engineering, and high-throughput omics.

A cytidine deaminase regulates axon regeneration by modulating the functions of the Caenorhabditis elegans HGF/plasminogen family protein SVH-1

The pathway for axon regeneration in Caenorhabditis elegans is activated by SVH-1, a growth factor belonging to the HGF/plasminogen family. SVH-1 is a dual-function factor that acts as an HGF-like growth factor to promote axon regeneration and as a protease to regulate early development. It is important to understand how SVH-1 is converted from a protease to a growth factor for axon regeneration. In this study, we demonstrate that cytidine deaminase (CDD) SVH-17/CDD-2 plays a role in the functional conversion of SVH-1. We find that the codon exchange of His-755 to Tyr in the Asp-His-Ser catalytic triad of SVH-1 can suppress the cdd-2 defect in axon regeneration. Furthermore, the stem hairpin structure around the His-755 site in svh-1 mRNA is required for the activation of axon regeneration by SVH-1. These results suggest that CDD-2 promotes axon regeneration by transforming the function of SVH-1 from a protease to a growth factor through modification of svh-1 mRNA.

Ciliary intrinsic mechanisms regulate dynamic ciliary extracellular vesicle release from sensory neurons

Extracellular vesicles (EVs) are submicron membranous structures and key mediators of intercellular communication.1,2 Recent research has highlighted roles for cilia-derived EVs in signal transduction, underscoring their importance as bioactive extracellular organelles containing conserved ciliary signaling proteins.3,4 Members of the transient receptor potential (TRP) channel polycystin-2 (PKD-2) family are found in ciliary EVs of the green algae Chlamydomonas and the nematode Caenorhabditis elegans5,6 and in EVs in the mouse embryonic node and isolated from human urine.7,8 In C. elegans, PKD-2 is expressed in male-specific EV-releasing sensory neurons, which extend ciliary tips to ciliary pore and directly release EVs into the environment.6,9 Males release EVs in a mechanically stimulated manner, regulate EV cargo content in response to mating partners, and deposit PKD-2::GFP-labeled EVs on the vulval cuticle of hermaphrodites during mating.9,10 Combined, our findings suggest that ciliary EV release is a dynamic process. Herein, we identify mechanisms controlling dynamic EV shedding using time-lapse imaging. Cilia can sustain the release of PKD-2-labeled EVs for 2 h. This extended release doesn't require neuronal transmission. Instead, ciliary intrinsic mechanisms regulate PKD-2 ciliary membrane replenishment and dynamic EV release. The kinesin-3 motor kinesin-like protein 6 (KLP-6) is necessary for initial and extended EV release, while the transition zone protein NPHP-4 is required only for sustained EV release. The dynamic replenishment of PKD-2 at the ciliary tip is key to sustained EV release. Our study provides a comprehensive portrait of real-time ciliary EV release and mechanisms supporting cilia as proficient EV release platforms.

Polycystins recruit cargo to distinct ciliary extracellular vesicle subtypes

Therapeutic use of tiny extracellular vesicles (EVs) requires understanding cargo loading mechanisms. Here, we used a modular proximity label approach to identify EV cargo associated with the transient potential channel (TRP) polycystin PKD-2 of C. elegans. Polycystins are conserved receptor-TRP channel proteins affecting cilium function; dysfunction causes polycystic kidney disease in humans and mating deficits in C. elegans. Polycystin-2 EV localization is conserved from algae to humans, hinting at an ancient and unknown function. We discovered that polycystins associate with and direct specific cargo to EVs: channel-like PACL-1, dorsal and ventral membrane C-type lectins PAMLs, and conserved tumor necrosis-associated factor (TRAF) signaling adaptors TRF-1 and TRF-2. Loading of these components relied on polycystin-1 LOV-1. Our modular EV-TurboID approach can be applied in both cell- and tissue-specific manners to define the composition of distinct EV subtypes, addressing a major challenge of the EV field.

C. elegans males optimize mate-preference decisions via sex-specific responses to multimodal sensory cues

For sexually reproducing animals, selecting optimal mates is important for maximizing reproductive fitness. In the nematode C. elegans, populations reproduce largely by hermaphrodite self-fertilization, but the cross-fertilization of hermaphrodites by males also occurs. Males' ability to recognize hermaphrodites involves several sensory cues, but an integrated view of the ways males use these cues in their native context to assess characteristics of potential mates has been elusive. Here, we examine the mate-preference behavior of C. elegans males evoked by natively produced cues. We find that males use a combination of volatile sex pheromones (VSPs), ascaroside sex pheromones, surface-associated cues, and other signals to assess multiple features of potential mates. Specific aspects of mate preference are communicated by distinct signals: developmental stage and sex are signaled by ascaroside pheromones and surface cues, whereas the presence of a self-sperm-depleted hermaphrodite is likely signaled by VSPs. Furthermore, males prefer to interact with virgin over mated, and well-fed over food-deprived, hermaphrodites; these preferences are likely adaptive and are also mediated by ascarosides and other cues. Sex-typical mate-preference behavior depends on the sexual state of the nervous system, such that pan-neuronal genetic masculinization in hermaphrodites generates male-typical social behavior. We also identify an unexpected role for the sex-shared ASH sensory neurons in male attraction to ascaroside sex pheromones. Our findings lead to an integrated view in which the distinct physical properties of various mate-preference cues guide a flexible, stepwise behavioral program by which males assess multiple features of potential mates to optimize mate preference.

Transport and barrier mechanisms that regulate ciliary compartmentalization and ciliopathies

Primary cilia act as cell surface antennae, coordinating cellular responses to sensory inputs and signalling molecules that regulate developmental and homeostatic pathways. Cilia are therefore critical to physiological processes, and defects in ciliary components are associated with a large group of inherited pleiotropic disorders - known collectively as ciliopathies - that have a broad spectrum of phenotypes and affect many or most tissues, including the kidney. A central feature of the cilium is its compartmentalized structure, which imparts its unique molecular composition and signalling environment despite its membrane and cytosol being contiguous with those of the cell. Such compartmentalization is achieved via active transport pathways that bring protein cargoes to and from the cilium, as well as gating pathways at the ciliary base that establish diffusion barriers to protein exchange into and out of the organelle. Many ciliopathy-linked proteins, including those involved in kidney development and homeostasis, are components of the compartmentalizing machinery. New insights into the major compartmentalizing pathways at the cilium, namely, ciliary gating, intraflagellar transport, lipidated protein flagellar transport and ciliary extracellular vesicle release pathways, have improved our understanding of the mechanisms that underpin ciliary disease and associated renal disorders.

Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches

Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly.

Early-life stress triggers long-lasting organismal resilience and longevity via tetraspanin

Early-life stress experiences can produce lasting impacts on organismal adaptation and fitness. How transient stress elicits memory-like physiological effects is largely unknown. Here, we show that early-life thermal stress strongly up-regulates tsp-1, a gene encoding the conserved transmembrane tetraspanin in C. elegans. TSP-1 forms prominent multimers and stable web-like structures critical for membrane barrier functions in adults and during aging. Increased TSP-1 abundance persists even after transient early-life heat stress. Such regulation requires CBP-1, a histone acetyltransferase that facilitates initial tsp-1 transcription. Tetraspanin webs form regular membrane structures and mediate resilience-promoting effects of early-life thermal stress. Gain-of-function TSP-1 confers marked C. elegans longevity extension and thermal resilience in human cells. Together, our results reveal a cellular mechanism by which early-life thermal stress produces long-lasting memory-like impact on organismal resilience and longevity.

Heat Shock Proteins Function as Signaling Molecules to Mediate Neuron-Glia Communication During Aging

The nervous system is primarily composed of neurons and glia, and the communication between them plays profound roles in regulating the development and function of the brain. Neuron-glia signal transduction is known to be mediated by secreted or juxtacrine signals through ligand-receptor interactions on the cell membrane. Here, we report a novel mechanism for neuron-glia signal transduction, wherein neurons transmit proteins to glia through extracellular vesicles, activating glial signaling pathways. We find that in the amphid sensory organ of Caenorhabditis elegans, different sensory neurons exhibit varying aging rates. This discrepancy in aging is governed by the crosstalk between neurons and glia. We demonstrate that early-aged neurons can transmit heat shock proteins (HSP) to glia via extracellular vesicles. These neuronal HSPs activate the IRE1-XBP1 pathway, further increasing their expression in glia, forming a positive feedback loop. Ultimately, the activation of the IRE1-XBP-1 pathway leads to the transcriptional regulation of chondroitin synthases to protect glia-embedded neurons from aging-associated functional decline. Therefore, our studies unveil a novel mechanism for neuron-glia communication in the nervous system and provide new insights into our understanding of brain aging.

Ciliary intrinsic mechanisms regulate dynamic ciliary extracellular vesicle release from sensory neurons

Cilia-derived extracellular vesicles (EVs) contain signaling proteins and act in intercellular communication. Polycystin-2 (PKD-2), a transient receptor potential channel, is a conserved ciliary EVs cargo. Caenorhabditis elegans serves as a model for studying ciliary EV biogenesis and function. C. elegans males release EVs in a mechanically-induced manner and deposit PKD-2-labeled EVs onto the hermaphrodite vulva during mating, suggesting an active release process. Here, we study the dynamics of ciliary EV release using time-lapse imaging and find that cilia can sustain the release of PKD-2-labeled EVs for a two-hour duration. Intriguingly, this extended release doesn't require neuronal synaptic transmission. Instead, ciliary intrinsic mechanisms regulate PKD-2 ciliary membrane replenishment and dynamic EV release. The ciliary kinesin-3 motor KLP-6 is necessary for both initial and extended ciliary EV release, while the transition zone protein NPHP-4 is required only for sustained EV release. The dihydroceramide desaturase DEGS1/2 ortholog TTM-5 is highly expressed in the EV-releasing sensory neurons, localizes to cilia, and is required for sustained but not initial ciliary EV release, implicating ceramide in ciliary ectocytosis. The study offers a comprehensive portrait of real-time ciliary EV release, and mechanisms supporting cilia as proficient EV release platforms.

Control of protein and lipid composition of photoreceptor outer segments-Implications for retinal disease

Vision is arguably our most important sense, and its loss brings substantial limitations to daily life for affected individuals. Light is perceived in retinal photoreceptors (PRs), which are highly specialized neurons subdivided into several compartments with distinct functions. The outer segments (OSs) of photoreceptors represent highly specialized primary ciliary compartments hosting the phototransduction cascade, which transforms incoming light into a neuronal signal. Retinal disease can result from various pathomechanisms originating in distinct subcompartments of the PR cell, or in the retinal pigment epithelium which supports the PRs. Dysfunction of primary cilia causes human disorders known as "ciliopathies", in which retinal disease is a common feature. This chapter focuses on PR OSs, discussing the mechanisms controlling their complex structure and composition. A sequence of tightly regulated sorting and trafficking events, both upstream of and within this ciliary compartment, ensures the establishment and maintenance of the adequate proteome and lipidome required for signaling in response to light. We discuss in particular our current understanding of the role of ciliopathy proteins involved in multi-protein complexes at the ciliary transition zone (CC2D2A) or BBSome (BBS1) and how their dysfunction causes retinal disease. While the loss of CC2D2A prevents the fusion of vesicles and delivery of the photopigment rhodopsin to the ciliary base, leading to early OS ultrastructural defects, BBS1 deficiency results in precocious accumulation of cholesterol in mutant OSs and decreased visual function preceding morphological changes. These distinct pathomechanisms underscore the central role of ciliary proteins involved in multiple processes controlling OS protein and lipid composition.

Nematodes Degrade Extracellular Antibiotic Resistance Genes by Secreting DNase II Encoded by the nuc-1 Gene

This study investigated the degradation performance and mechanism of extracellular antibiotic resistance genes (eARGs) by nematodes using batch degradation experiments, mutant strain validation, and phylogenetic tree construction. Caenorhabditis elegans, a representative nematode, effectively degraded approximately 99.999% of eARGs (tetM and kan) in 84 h and completely deactivated them within a few hours. Deoxyribonuclease (DNase) II encoded by nuc-1 in the excretory and secretory products of nematodes was the primary mechanism. A neighbor-joining phylogenetic tree indicated the widespread presence of homologs of the NUC-1 protein in other nematodes, such as Caenorhabditis remanei and Caenorhabditis brenneri, whose capabilities of degrading eARGs were then experimentally confirmed. C. elegans remained effective in degrading eARGs under the effects of natural organic matter (5, 10, and 20 mg/L, 5.26-6.22 log degradation), cation (2.0 mM Mg2+ and 2.5 mM Ca2+, 5.02-5.04 log degradation), temperature conditions (1, 20, and 30 °C, 1.21-5.26 log degradation), and in surface water and wastewater samples (4.78 and 3.23 log degradation, respectively). These findings highlight the pervasive but neglected role of nematodes in the natural decay of eARGs and provide novel approaches for antimicrobial resistance mitigation biotechnology by introducing nematodes to wastewater, sludge, and biosolids.

Small extracellular vesicle-mediated metabolic reprogramming: from tumors to pre-metastatic niche formation

Metastasis, the spread of a tumor or cancer from the primary site of the body to a secondary site, is a multi-step process in cancer progression, accounting for various obstacles in cancer treatment and most cancer-related deaths. Metabolic reprogramming refers to adaptive metabolic changes that occur in cancer cells in the tumor microenvironment (TME) to enhance their survival ability and metastatic potential. Stromal cell metabolism also changes to stimulate tumor proliferation and metastasis. Metabolic adaptations of tumor and non-tumor cells exist not only in the TME but also in the pre-metastatic niche (PMN), a remote TME conducive for tumor metastasis. As a novel mediator in cell-to-cell communication, small extracellular vesicles (sEVs), which have a diameter of 30-150 nm, reprogram metabolism in stromal and cancer cells within the TME by transferring bioactive substances including proteins, mRNAs and miRNAs (microRNAs). sEVs can be delivered from the primary TME to PMN, affecting PMN formation in stroma rewriting, angiogenesis, immunological suppression and matrix cell metabolism by mediating metabolic reprogramming. Herein, we review the functions of sEVs in cancer cells and the TME, how sEVs facilitate PMN establishment to trigger metastasis via metabolic reprogramming, and the prospective applications of sEVs in tumor diagnosis and treatment. Video Abstract.

Exosomes, microvesicles, and other extracellular vesicles-a Keystone Symposia report

Extracellular vesicles (EVs) are small, lipid-bilayer-bound particles released by cells that can contain important bioactive molecules, including lipids, RNAs, and proteins. Once released in the extracellular environment, EVs can act as messengers locally as well as to distant tissues to coordinate tissue homeostasis and systemic responses. There is a growing interest in not only understanding the physiology of EVs as signaling particles but also leveraging them as minimally invasive diagnostic and prognostic biomarkers (e.g., they can be found in biofluids) and drug-delivery vehicles. On October 30-November 2, 2022, researchers in the EV field convened for the Keystone symposium "Exosomes, Microvesicles, and Other Extracellular Vesicles" to discuss developing standardized language and methodology, new data on the basic biology of EVs and potential clinical utility, as well as novel technologies to isolate and characterize EVs.

C. elegans males optimize mate-choice decisions via sex-specific responses to multimodal sensory cues

For sexually reproducing animals, selecting optimal mates is essential for maximizing reproductive fitness. Because the nematode C. elegans reproduces mostly by self-fertilization, little is known about its mate-choice behaviors. While several sensory cues have been implicated in males' ability to recognize hermaphrodites, achieving an integrated understanding of the ways males use these cues to assess relevant characteristics of potential mates has proven challenging. Here, we use a choice-based social-interaction assay to explore the ability of C. elegans males to make and optimize mate choices. We find that males use a combination of volatile sex pheromones (VSPs), ascaroside pheromones, surface-bound chemical cues, and other signals to robustly assess a variety of features of potential mates. Specific aspects of mate choice are communicated by distinct signals: the presence of a sperm-depleted, receptive hermaphrodite is likely signaled by VSPs, while developmental stage and sex are redundantly specified by ascaroside pheromones and surface-associated cues. Ascarosides also signal nutritional information, allowing males to choose well-fed over starved mates, while both ascarosides and surface-associated cues cause males to prefer virgin over previously mated hermaphrodites. The male-specificity of these behavioral responses is determined by both male-specific neurons and the male state of sex-shared circuits, and we reveal an unexpected role for the sex-shared ASH sensory neurons in male attraction to endogenously produced hermaphrodite ascarosides. Together, our findings lead to an integrated view of the signaling and behavioral mechanisms by which males use diverse sensory cues to assess multiple features of potential mates and optimize mate choice.

C. elegans vab-6 encodes a KIF3A kinesin and functions cell non-autonomously to regulate epidermal morphogenesis

Cells undergo strict regulation to develop their shape in a process called morphogenesis. Caenorhabditis elegans with mutations in the variable abnormal (vab) class of genes have been shown to display epidermal and neuronal morphological defects. While several vab genes have been well-characterized, the function of the vab-6 gene remains unknown. Here, we show that vab-6 is synonymous with a subunit of the kinesin-II heterotrimeric motor complex called klp-20/Kif3a, a motor well-understood to be involved in developing sensory cilia in the nervous system. We show that certain klp-20 alleles cause animals to develop a bumpy body phenotype that is variable but most severe in mutants containing single amino-acid substitutions in the catalytic head-domain sites of the protein. Surprisingly, animals carrying a klp-20 null allele do not show the bumpy epidermal phenotype suggesting genetic redundancy and only when mutant versions of the KLP-20 protein are present, the epidermal phenotype is observed. The bumpy epidermal phenotype was not observed in other kinesin-2 mutants, suggesting that KLP-20 is functioning independently from its role in intraflagellar transport (IFT) during ciliogenesis. Interestingly, despite having such a prominent epidermal phenotype, KLP-20 is not expressed in the epidermis, strongly suggesting a cell non-autonomous role in which it regulates epidermal morphogenesis.

Cilia-Derived Extracellular Vesicles in Caenorhabditis Elegans: In Vivo Imaging and Quantification of Extracellular Vesicle Release and Capture

Caenorhabditis elegans is a microscopic model nematode characterized by body transparency and ease of genetic manipulation. Release of extracellular vesicles (EVs) is observed from different tissues; of particular interest are the EVs released by the cilia of sensory neurons. C. elegans ciliated sensory neurons produce EVs that are environmentally released and/or captured by neighboring glial cells. In this chapter, we describe a methodological approach to image the biogenesis, release, and capture of EVs by glial cells in anesthetized animals. This method will allow the experimenter to visualize and quantify the release of ciliary-derived EVs.

Neuronal cilia in energy homeostasis

A subset of genetic disorders termed ciliopathies are associated with obesity. The mechanisms behind cilia dysfunction and altered energy homeostasis in these syndromes are complex and likely involve deficits in both development and adult homeostasis. Interestingly, several cilia-associated gene mutations also lead to morbid obesity. While cilia have critical and diverse functions in energy homeostasis, including their roles in centrally mediated food intake and peripheral tissues, many questions remain. Here, we briefly discuss syndromic ciliopathies and monogenic cilia signaling mutations associated with obesity. We then focus on potential ways neuronal cilia regulate energy homeostasis. We discuss the literature around cilia and leptin-melanocortin signaling and changes in ciliary G protein-coupled receptor (GPCR) signaling. We also discuss the different brain regions where cilia are implicated in energy homeostasis and the potential for cilia dysfunction in neural development to contribute to obesity. We close with a short discussion on the challenges and opportunities associated with studies looking at neuronal cilia and energy homeostasis. This review highlights how neuronal cilia-mediated signaling is critical for proper energy homeostasis.

Kinesin-2 motors differentially impact biogenesis of extracellular vesicle subpopulations shed from sensory cilia

Extracellular vesicles (EVs) are bioactive lipid-bilayer enclosed particles released from nearly all cells. One specialized site for EV shedding is the primary cilium. Here, we discover the conserved ion channel CLHM-1 as a ciliary EV cargo. Imaging of EVs released from sensory neuron cilia of Caenorhabditis elegans expressing fluorescently tagged CLHM-1 and TRP polycystin-2 channel PKD-2 shows enrichment of these cargoes in distinct EV subpopulations that are differentially shed in response to mating partner availability. PKD-2 alone is present in EVs shed from the cilium distal tip, whereas CLHM-1 EVs bud from a secondary site(s), including the ciliary base. Heterotrimeric and homodimeric kinesin-2 motors have discrete impacts on PKD-2 and CLHM-1 colocalization in both cilia and EVs. Total loss of kinesin-2 activity decreases shedding of PKD-2 but not CLHM-1 EVs. Our data demonstrate that anterograde intraflagellar transport is required for selective enrichment of protein cargoes into heterogeneous EVs with different signaling potentials.

Identification of Downregulated Exosome-Associated Gene ENPP1 as a Novel Lipid Metabolism and Immune-Associated Biomarker for Hepatocellular Carcinoma

Exosome plays an important role in the occurrence and development of tumors, such as hepatocellular carcinoma (LIHC). However, the functions and mechanisms of exosome-associated molecules in LIHC are still underexplored. Here, we investigated the role of the exosome-related gene ENPP1 in LIHC. Comprehensive bioinformatics from multiple databases revealed that ENPP1 was significantly downregulated in LIHC tissues. The patients with downregulated ENPP1 displayed a poor prognosis. Immunohistochemistry (IHC) was used to further confirm the downregulated ENPP1 in LIHC tissues. In addition, the coexpression network of ENPP1 was also explored to understand its roles in the underlying signaling pathways, including fatty acid degradation and the PPAR signaling pathway. Simultaneously, GSEA analysis indicated the potential roles of ENPP1 in the lipid metabolism-associated signaling pathways in the pathogenesis of LIHC, including fatty acid metabolism, fatty acid synthesis, and so on. Finally, immunological analysis indicated that ENPP1 might also be involved in multiple immune-related features, including immunoinhibitors, immunostimulators, and chemokines. Taken together, these findings could enhance our understanding of ENPP1 in LIHC pathogenesis and immune response and provide a new target for ENPP1-related immunotherapy in clinical treatment.