Native architecture of the centriole proximal region reveals features underlying its 9-fold radial symmetry.
BACKGROUND
Centrioles are cylindrical microtubule-based structures whose assembly is critical for the formation of cilia, flagella, and centrosomes. The centriole proximal region harbors a cartwheel that dictates the 9-fold symmetry of centrioles. Although the cartwheel architecture has been recently analyzed, how it connects to the peripheral microtubules is not understood. More generally, a high-resolution view of the proximal region of the centriole is lacking, thus limiting understanding of the underlying assembly mechanisms.


RESULTS
We report the complete architecture of the Trichonympha centriole proximal region using cryotomography. The resulting 3D map reveals several features, including additional densities in the cartwheel that exhibit a 9-fold symmetrical arrangement, as well as the structure of the Pinhead and the A-C linker that connect to microtubules. Moreover, we uncover striking chiral features that might impart directionality to the entire centriole. Furthermore, we identify Trichonympha SAS-6 and demonstrate that it localizes to the cartwheel in vivo.


CONCLUSIONS
Our work provides unprecedented insight into the architecture of the centriole proximal region, which is key for a thorough understanding of the mechanisms governing centriole assembly.
Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland.
Paul
P
Guichard
Virginie
V
Hachet
Norbert
N
Majubu
Aitana
A
Neves
Davide
D
Demurtas
Natacha
N
Olieric
Isabelle
I
Fluckiger
Akinori
A
Yamada
Kumiko
K
Kihara
Yuichiro
Y
Nishida
Shigeharu
S
Moriya
Michel O
MO
Steinmetz
Yuichi
Y
Hongoh
Pierre
P
Gönczy
D000818:Animals; D002502:Centrioles; D056952:Hypermastigia / Q000166:cytology; D008969:Molecular Sequence Data