The extracellular matrix gene <i>mec-9</i> regulates <i>C. elegans</i> 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 <i>C. elegans</i> as a model, we found that a neomorphic mutation in the ECM gene <i>mec-9</i> impacts sensory cilia function, ciliary protein localization, microtubule ultrastructure, and shedding of ciliary extracellular vesicles (EVs). We show that <i>mec-9</i> 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 <i>mec-9</i> in the <i>C. elegans</i> ciliated nervous system and provide an <i>in vivo</i> model to study the relationship between cilia and ECM.