Abstract
Centrioles are cell organelles consisting of nine triplet microtubules arranged in rotational symmetry. This structure is highly conserved among various eukaryotic organisms and serves as the template for the “9 + 2” or “9 + 0” structures of ciliary axonemes. How this nine-fold symmetrical structure forms is a long-standing question. Recently, genetic approaches using Chlamydomonas revealed that the cartwheel, a sub-centriolar structure with a hub and nine spokes, plays a pivotal role in the establishment of nine-fold symmetry, and that a protein called SAS-6 is a key component of the cartwheel assembly. This review summarizes the Chlamydomonas studies and recent advances in the understanding the SAS-6 function.
