Figure 4. Centrioles formed through de novo assembly are error-prone.
(A–C) Isogenic SAS-6-/-; p53-/- cells carrying indicated SAS-6 constructs (see ‘Methods’) were induced to express indicated SAS-6 mutants for 3 days, and then processed for serial sectioning electron microscopy. (A1) A mature, SAS-6FL-derived centriole missed three MT triplets but was able to duplicate, producing daughter centrioles also made of an incomplete set of MT triplets (see stars in sections I and II). It appears that two daughter centrioles were formed at the same time. (A2) A mature, SAS-6FL-derived centriole 33% wider than normal centrioles was able to acquire appendages. (A3) A SAS-6FL-derived centriole made of disorganized MTs. (A4&5) Cross-sectional views of SAS-6FL-derived, abnormal centrioles missing MT triplets. (A6) A SAS-6FL-derived centriole carrying 9 MT triplets (arrow heads) but existing as a distorted open cylinder (arrow). (B) Abnormal centrioles derived from SAS-6DM4 were shown in cross-sectional or longitudinal views. (C) Abnormal centrioles derived from SAS-6F131E were shown in cross-sectional views. Note that a larger centriole made of 11 MT triplets was shown (C1). (D) The outer diameter of centrioles was quantified for both canonical centrioles (in normal RPE1 cells), and SAS-6FL-derived de novo centrioles. (E) Quantifications showing the error rates of de novo and canonical centrioles. Sample size (n) is indicated. Note that arrows in all images indicate the missing of MT triplets.