title: Centrosomes and spindles in ascidian embryos and eggs.
abstract: During embryonic development and maternal meiotic maturation, positioning of the mitotic/meiotic spindle is subject to control mechanisms that meet the needs of the particular cell type. Here we review the methods, molecular tools, and the ascidian model we use to study three different ways in which centrosomes or spindles are positioned in three different cellular contexts. First, we review unequal cleavage in the ascidian germ lineage. In the germ cell precursors, a large macromolecular structure termed the centrosome-attracting body causes three successive rounds of unequal cleavage from the 8- to the 64-cell stage. Next, we discuss spindle positioning underlying the invariant cleavage pattern. Ascidian embryos display an invariant cleavage pattern whereby the mitotic spindle aligns in a predetermined orientation in every blastomere up to the gastrula stage (composed of 112 cells). Finally, we review methods and approaches to study meiotic spindle positioning in eggs.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, and CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Villefranche-sur-Mer, France.
authors.forename: Alex
authors.initials: A
authors.lastname: McDougall
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, and CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Villefranche-sur-Mer, France.
authors.forename: Janet
authors.initials: J
authors.lastname: Chenevert
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, and CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Villefranche-sur-Mer, France.
authors.forename: Gerard
authors.initials: G
authors.lastname: Pruliere
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, and CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Villefranche-sur-Mer, France.
authors.forename: Vlad
authors.initials: V
authors.lastname: Costache
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, and CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Villefranche-sur-Mer, France.
authors.forename: Celine
authors.initials: C
authors.lastname: Hebras
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, and CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Villefranche-sur-Mer, France.
authors.forename: Gregory
authors.initials: G
authors.lastname: Salez
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, and CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Villefranche-sur-Mer, France.
authors.forename: Remi
authors.initials: R
authors.lastname: Dumollard
mesh_terms: D000818:Animals; D018385:Centrosome / Q000648:ultrastructure*; D004625:Embryo, Nonmammalian / Q000648:ultrastructure; D008297:Male; D008856:Microscopy, Fluorescence; D010063:Ovum / Q000648:ultrastructure; D008941:Spindle Apparatus / Q000648:ultrastructure*; D014561:Urochordata / Q000648:ultrastructure
keywords: Ascidian; Centrosome; Invariant cleavage; Live cell imaging; Polar body; Spindle pole; Unequal cleavage