Extracellular vesicles (EVs) are nano-sized packages released by cells that function in intercellular communication. Cilia are hair-like projections that play important roles in development and signaling. The cilium both releases and binds to EVs. EVs play a role in cell signaling in health and pathologies, and may carry beneficial or toxic cargo. A fundamental understanding of the biogenesis, release, uptake, and signaling of ciliary EVs is lacking. Here, we demonstrate the utility of the nematode C.elegans as a model to identify the molecules and mechanisms that play a role in EV biology and function.
A subset of the ciliated neurons of C.elegans release EVs containing select cargo into the environment. These cargo include the polycystins LOV-1 and PKD-2. C.elegans EVs regulate the mating behaviors in a cargo-dependent manner. Using a candidate gene approach combined with live imaging of mutants that express GFP-tagged EV cargo, we are determining mechanisms driving biogenesis and release. Defects in the release of GFP-tagged EV cargo from the tips of EV releasing neurons (EVNs) and/or the accumulation of GFP-tagged EV cargo at the base of the EVNs indicates defects in EV biogenesis and/or release. We then use Transmission Electron Microscopy to determine whether the gene is required for EV biogenesis or EV release. Using these approaches, we have uncovered a requirement for cilia, the intraflagellar transport (IFT) machinery, a ciliary kinesin KLP-6, a stress-activated p38 MAPK PMK-1, and a novel myristoylated protein CIL-7. We are now determining whether a RAB protein and a phospholipid flippase play a role in ciliary EV biology. Thus, C.elegans can be used to study the relationship between cilia and EVs, and also identify the factors that regulate EV composition and function in health and disease.
Future studies are aimed at the identification of EV cargo, environmental conditions, and the components that regulate the biogenesis and release of EVs containing distinct cargoes. .