C. elegans PEZO-1 is a mechanosensitive ion channel involved in food sensation.

PIEZO channels are force sensors essential for physiological processes, including baroreception and proprioception. The Caenorhabditis elegans genome encodes an orthologue gene of the Piezo family, pezo-1, which is expressed in several tissues, including the pharynx. This myogenic pump is an essential component of the C. elegans alimentary canal, whose contraction and relaxation are modulated by mechanical stimulation elicited by food content. Whether pezo-1 encodes a mechanosensitive ion channel and contributes to pharyngeal function remains unknown. Here, we leverage genome editing, genetics, microfluidics, and electropharyngeogram recording to establish that pezo-1 is expressed in the pharynx, including in a proprioceptive-like neuron, and regulates pharyngeal function. Knockout (KO) and gain-of-function (GOF) mutants reveal that pezo-1 is involved in fine-tuning pharyngeal pumping frequency, as well as sensing osmolarity and food mechanical properties. Using pressure-clamp experiments in primary C. elegans embryo cultures, we determine that pezo-1 KO cells do not display mechanosensitive currents, whereas cells expressing wild-type or GOF PEZO-1 exhibit mechanosensitivity. Moreover, infecting the Spodoptera frugiperda cell line with a baculovirus containing the G-isoform of pezo-1 (among the longest isoforms) demonstrates that pezo-1 encodes a mechanosensitive channel. Our findings reveal that pezo-1 is a mechanosensitive ion channel that regulates food sensation in worms.

Quantitative RNA-seq meta-analysis of alternative exon usage in C. elegans.

Almost 20 years after the completion of the C. elegans genome sequence, gene structure annotation is still an ongoing process with new evidence for gene variants still being regularly uncovered by additional in-depth transcriptome studies. While alternative splice forms can allow a single gene to encode several functional isoforms, the question of how much spurious splicing is tolerated is still heavily debated. Here we gathered a compendium of 1682 publicly available C. elegans RNA-seq data sets to increase the dynamic range of detection of RNA isoforms, and obtained robust measurements of the relative abundance of each splicing event. While most of the splicing reads come from reproducibly detected splicing events, a large fraction of purported junctions is only supported by a very low number of reads. We devised an automated curation method that takes into account the expression level of each gene to discriminate robust splicing events from potential biological noise. We found that rarely used splice sites disproportionately come from highly expressed genes and are significantly less conserved in other nematode genomes than splice sites with a higher usage frequency. Our increased detection power confirmed trans-splicing for at least 84% of C. elegans protein coding genes. The genes for which trans-splicing was not observed are overwhelmingly low expression genes, suggesting that the mechanism is pervasive but not fully captured by organism-wide RNA-seq. We generated annotated gene models including quantitative exon usage information for the entire C. elegans genome. This allows users to visualize at a glance the relative expression of each isoform for their gene of interest.

Omega-3 Fatty Acids Modulate TRPV4 Function through Plasma Membrane Remodeling.

Dietary consumption of ω-3 polyunsaturated fatty acids (PUFAs), present in fish oils, is known to improve the vascular response, but their molecular targets remain largely unknown. Activation of the TRPV4 channel has been implicated in endothelium-dependent vasorelaxation. Here, we studied the contribution of ω-3 PUFAs to TRPV4 function by precisely manipulating the fatty acid content in Caenorhabditis elegans. By genetically depriving the worms of PUFAs, we determined that the metabolism of ω-3 fatty acids is required for TRPV4 activity. Functional, lipid metabolome, and biophysical analyses demonstrated that ω-3 PUFAs enhance TRPV4 function in human endothelial cells and support the hypothesis that lipid metabolism and membrane remodeling regulate cell reactivity. We propose a model whereby the eicosanoid's epoxide group location increases membrane fluidity and influences the endothelial cell response by increasing TRPV4 channel activity. ω-3 PUFA-like molecules might be viable antihypertensive agents for targeting TRPV4 to reduce systemic blood pressure.

An Abundant Class of Non-coding DNA Can Prevent Stochastic Gene Silencing in the C. elegans Germline.

Cells benefit from silencing foreign genetic elements but must simultaneously avoid inactivating endogenous genes. Although chromatin modifications and RNAs contribute to maintenance of silenced states, the establishment of silenced regions will inevitably reflect underlying DNA sequence and/or structure. Here, we demonstrate that a pervasive non-coding DNA feature in Caenorhabditis elegans, characterized by 10-base pair periodic An/Tn-clusters (PATCs), can license transgenes for germline expression within repressive chromatin domains. Transgenes containing natural or synthetic PATCs are resistant to position effect variegation and stochastic silencing in the germline. Among endogenous genes, intron length and PATC-character undergo dramatic changes as orthologs move from active to repressive chromatin over evolutionary time, indicating a dynamic character to the An/Tn periodicity. We propose that PATCs form the basis of a cellular immune system, identifying certain endogenous genes in heterochromatic contexts as privileged while foreign DNA can be suppressed with no requirement for a cellular memory of prior exposure.

The 5A apolipoprotein A-I mimetic peptide displays antiinflammatory and antioxidant properties in vivo and in vitro.

OBJECTIVE: The apolipoprotein (apo)A-I mimetic peptide 5A is highly specific for ATP-binding cassette transporter (ABC)A1-mediated cholesterol efflux. We investigated whether the 5A peptide shares other beneficial features of apoA-I, such as protection against inflammation and oxidation. Methods- New Zealand white rabbits received an infusion of apoA-I, reconstituted high-density lipoprotein (HDL) containing apoA-I ([A-I]rHDL), or the 5A peptide complexed with phospholipids (1-palmitoyl-2-linoleoyl phosphatidylcholine [PLPC]), before inserting a collar around the carotid artery. Human coronary artery endothelial cells (HCAECs) were incubated with (A-I)rHDL or 5A/PLPC before stimulation with tumor necrosis factor alpha. Results- ApoA-I, (A-I)rHDL, and 5A/PLPC reduced the collar-mediated increase in (1) endothelial expression of cell adhesion molecules vascular cell adhesion molecule-1 and intercellular adhesion molecule-1; (2) production, as well as the expression of the Nox4 catalytic subunits of the NADPH oxidase; and (3) infiltration of circulating neutrophils into the carotid intima-media. In HCAECs, both 5A/PLPC and (A-I)rHDL inhibited tumor necrosis factor-alpha-induced intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression, as well as the nuclear factor kappaB signaling cascade and production. The effects of the 5A/PLPC complex were no longer apparent in HCAECs knocked down for ABCA1. CONCLUSIONS: Like apoA-I, the 5A peptide inhibits acute inflammation and oxidative stress in rabbit carotids and HCAECs. In vitro, the 5A peptide exerts these beneficial effects through interaction with ABCA1.