Procentrioles over-elongate during prolonged mitosis. (A) The analysis of procentriole length in cycling cells during mitosis and G1. Average PC length, SD, and centriole number are indicated below images. (B, D, and E) Examples of expanded centrioles arrested in S phase (by HU), G2 (by RO 3306, RO) and in mitosis (by monastrol). Centrioles were immunolabeled for acetylated tubulin. (C) EM analysis of procentriole length in cells arrested in S phase by HU. (F and G) Quantification of centriole length under various experimental conditions using expansion and acetylated tubulin labeling. (H) Examples of over-elongated procentrioles from mitotically arrested cells immunolabeled for acetylated tubulin and distal centriole protein Cep290. (I) Examples of over-elongated procentrioles analyzed by EM. (J) Quantification of centriole phenotypes in expanded mitotically arrested cells of various cell lines. Procentrioles were scored for the length of their acetylated tubulin signals. Cells were placed in the green or blue category by the presence of at least one procentriole of indicated length. Cells with both procentrioles shorter than ∼500 nm were placed in the gray category. Centriole counts are from 2, 2, 1, 5, 2, and 2 independent experiments, respectively. MC, mother centriole; PC, procentriole. Prometa, prometaphase; Meta, metaphase; Ana, anaphase; Telo, telophase. Scale bars, 0.5 µm in A and I; 2 µm in B, D, and H; 4 µm in E; 0.4 µm in C.