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 γ-tubulin ring complex (γTuRC). The widely accepted view is that γTuRC localizes to the pericentriolar material (PCM), where it nucleates microtubules. γTuRC 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 γTuRC 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 γTuRC mutant fibroblasts derived from a patient suffering from microcephaly with chorioretinopathy. These results identify a novel, non-canonical role of augmin-γTuRC in the centriole lumen that is linked to human disease.

Centrosome linker diversity and its function in centrosome clustering and mitotic spindle formation

“…How C-Nap1 that only associates at the proximal end of centrioles contributes to c-tubulin recruitment is presently unclear. C-Nap1 could have an impact on CEP192 localization or activity that recruits the c-tubulin ring complex to the PCM of interphase centrioles (Schweizer et al, 2021). Since in RPE1 cells, centrosome cohesion is very efficient even in the absence of MTs (Figs 1B and 2A), it is unlikely that the MT-promoting activity of C-Nap1 and Ninein contributes to the function of the centrosome linker.…”

Nine‐fold symmetry of centriole: The joint efforts of its core proteins

“…U‐ExM revealed that γTuRC also localizes in the centriole lumen, necessary for centriole integrity and cilium assembly. [ 37,104 ] Another method of expansion microscopy, magnified analysis of the proteome (MAP), [ 105 ] revealed that the centriole microtubules are ubiquitously acetylated and the centriole length can be defined by the labeling of acetylated tubulin. [ 106 ] Apart from C .…”

ENKD1 is a centrosomal and ciliary microtubule-associated protein important for primary cilium assembly and Hedgehog signaling

“…To this end, we analyzed its localization at different stages of the cell cycle using ultrastructure expansion microscopy (U-ExM) that allows nanoscale mapping of proteins at the centrosomes and cilia (Gambarotto et al, 2019). RPE1::mNG-ENKD1 cells were stained for acetylated tubulin, which marks the centriole wall and gamma-tubulin, which marks the pericentriolar material and the centriole lumen (Schweizer et al, 2020). ENKD1 localized to resolvable rings at the outer, proximal part of the centrioles in interphase and metaphase cells and the diameter of its rings were smaller than that of gamma-tubulin rings (Fig.…”