Condensation of pericentrin proteins in human cells illuminates phase separation in centrosome assembly

Mitotic centrosomes are complex membraneless organelles that guide the formation of mitotic spindles to ensure faithful cell division. They are formed by timely expansion of the pericentriolar material (PCM) around the centrioles at the onset of mitosis. How PCM proteins are recruited and held together without a lipid membrane remains elusive. Here we found that endogenously expressed pericentrin (PCNT), a conserved PCM scaffold protein, condenses into liquid-like granules during early mitosis in cultured human cells. Furthermore, the N-terminal segment of PCNT, enriched with conserved coiled-coils and low-complexity regions (LCRs), undergoes phase separation. These PCNT 9condensates9 selectively recruit PCM components and nucleate microtubules in cells. We propose that coiled-coils and LCRs, two prevalent sequence features in the centrosomal proteome, are preserved under evolutionary pressure to drive phase separation, a process that bestows upon the centrosome a distinct material property critical for its assembly and functions.