SAS-1 and SSNA-1 form dynamic centriolar satellites in C. elegans

Centriolar satellites are dynamic pericentrosomal assemblies that regulate centrosomal protein homeostasis and ciliogenesis. While extensively characterized in vertebrates, their existence and assembly principles in other systems are less well understood. Here, we identify SAS-1 and its interaction partner SSNA-1 as core components of centriolar satellite-like structures in C. elegans . We show that SAS-1 satellites occupy a previously unrecognized centrosomal layer positioned between the pericentriolar material and a specialized endoplasmic reticulum. SAS-1 satellites exhibit many features of biomolecular condensates, such as dose-dependent formation, rapid dynamics, and sensitivity to disruption of weak hydrophobic interactions, while their organization depends on the microtubule cytoskeleton. Mechanistically we identify the unstructured and so far, uncharacterized N-terminal region of SAS-1 being functionally important for embryonic viability, satellite formation and binding to microtubules. Our findings demonstrate that C. elegans . possesses bona fide centriolar satellites that share many features with vertebrate satellites, highlighting their evolutionary conservation and importance across species.