Sub-centrosomal mapping identifies augmin-γTuRC as part of a centriole-stabilizing scaffold

Abstract

Centriole biogenesis and maintenance are crucial for cells to generate cilia and assemble centrosomes that function as microtubule organizing centers (MTOCs). Centriole biogenesis and MTOC function both require the microtubule nucleator {gamma}-tubulin ring complex ({gamma}TuRC). The widely accepted view is that {gamma}TuRC localizes to the pericentriolar material (PCM), where it nucleates microtubules. {gamma}TuRC has also been observed at centriolar regions that lack PCM, but the significance of these findings is unclear. Here we have used expansion microscopy to map spatially and functionally distinct sub-populations of centrosomal {gamma}TuRC including in the centriole lumen. Luminal localization is mediated by augmin and both complexes are linked to the centriole inner scaffold through POC5. Disruption of luminal localization impairs centriole stability and cilia assembly, defects that are also observed in {gamma}TuRC mutant fibroblasts derived from a patient suffering from microcephaly with chorioretinopathy. These results identify a novel, non-canonical role of augmin-{gamma}TuRC in the centriole lumen that is linked to human disease.