The extracellular matrix gene mec-9 regulates C. elegans sensory cilia

Cilia are critical sensory organelles that project from the cell surface into the tissue environment, where they are surrounded by extracellular matrix (ECM). Abnormal ECM and fibrosis are two hallmarks of ciliopathies, yet the relationship between cilia and ECM is not well understood. Using the sense organs of C. elegans as a model, we found that a neomorphic mutation in the ECM gene mec-9 impacts sensory cilia function, ciliary protein localization, microtubule ultrastructure, and shedding of ciliary extracellular vesicles (EVs). We show that mec-9 is not expressed in EV releasing neurons, but rather by companion neurons in the sense organs, and may act cell non-autonomously. Our studies reveal pleiotropic roles for mec-9 in the C. elegans ciliated nervous system and provide an in vivo model to study the relationship between cilia and ECM.