Mode of centriole duplication and distribution.

R S Kochanski,G G Borisy

doi:10.1083/jcb.110.5.1599

Abstract

Centriole stability and distribution during the mammalian cell cycle was studied by microinjecting biotinylated tubulin into early G1 cells and analyzing the pattern of incorporation into centrioles. Cells were extracted and cold treated to depolymerize labile microtubules, allowing the fluorescent microscopic visualization of the stable centrioles. The ability to detect single centrioles was confirmed by use of correlative electron microscopy. Indirect hapten and immunofluorescent labeling of biotinylated and total tubulin permitted us to distinguish newly formed from preexisting centrioles. Daughter centrioles incorporated biotinylated tubulin, and at mitosis each cell received a centrosome containing one new and one old centriole. We conclude that in each cell cycle tubulin incorporation into centrioles is conservative, and centriole distribution is semiconservative.

Highlights

Centriole stability and distribution during the mammalian cell cycle was studied by microinjecting biotinylated tubulin into early G~ cells and analyzing the pattern of incorporation into centrioles
How are centrioles duplicated and distributed to daughter cells? Previously, the centriole cycle had been studied by electron microscopy of cells fixed at successive stages of the cell cycle (Robbins et al, 1968; Rieder and Borisy, 1982; Vorobyev and Chentsov, 1982), or from analysis of centrioles isolated from populations of synchronized cells (Kuriyama and Borisy, 1981)
We confirm the interpretations of previous studies based on electron microscopy

Summary

Introduction

Centriole stability and distribution during the mammalian cell cycle was studied by microinjecting biotinylated tubulin into early G~ cells and analyzing the pattern of incorporation into centrioles. A pair of centrioles begins the cycle in orthogonal configuration They lose their orthogonal relationship (disorientation) in early Gj phase. The centriole pairs are distributed to the daughter cells and the cycle is completed. The morphological relationships of the centriole cycle strongly suggest that the parent is conserved and that the daughter is newly formed, but micrographs of fixed cells provide only static images of a dynamic process. Centrioles double in number each typical animal cell cycle and so their number remains stable. They sometimes arise de novo, without a visible precursor (reviewed by Wheatley, 1982; Vorobyev and Nadezhdina, 1987), indicating that their formation does not require a preexisting mature centriole.

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