Centriolar satellites assemble via a hierarchical pathway driven by PCM1 multimerization

Centriolar satellites (CS) are ubiquitous membraneless organelles with diverse functions and links to developmental and neuronal diseases. However, the molecular principles governing their assembly and regulation remain poorly understood. To address this, we developed cellular and in vitro biogenesis assays that enable spatiotemporal quantification of CS granule properties during assembly, remodeling, and maintenance. Using these tools, we show that CS assemble via a hierarchical pathway initiated by pericentriolar material-1 (PCM1) scaffold formation and followed by client recruitment. PCM1 intrinsically assembles into granules through multimerization, a process modulated by the cytoskeleton. High-resolution imaging revealed that PCM1 and its clients occupy distinct subdomains with different compositions and dynamics. Perturbing PCM1 multimerization impaired ciliary signaling and mitotic progression, underscoring its functional importance. Together, these findings define the molecular basis of CS biogenesis, establish tools to probe CS regulation, and provide a framework for understanding how CS deregulation contributes to disease. More broadly, these may extend to other membraneless organelles and help explain their specificity and plasticity.