Acentrosomal spindle assembly and chromosome segregation during oocyte meiosis

Abstract

The ability to reproduce relies in most eukaryotes on specialized cells called gametes. Gametes are formed by the process of meiosis in which, after a single round of replication, two successive cell divisions reduce the ploidy of the genome. Fusion of gametes at fertilization reconstitutes diploidy. In most animal species, chromosome segregation during female meiosis occurs on spindles assembled in the absence of the major microtubule-organizing center, the centrosome. In mammals, oocyte meiosis is error-prone and underlies the majority of birth aneuploidies. Here, we review recent work on acentrosomal spindle formation and chromosome alignment/separation during oocyte meiosis in different animal models.

Chromatin-induced spindle assembly plays an important role in metaphase congression of silkworm holocentric chromosomes

“…we detected the accumulation of tubulin around chromosomes in silkworm BmN4 cells in 1 prometaphase, which is similar to the assembly of acentrosomal spindles observed during 2 meiosis in oocytes (Dumont and Desai, 2012 Confocal three-dimensional reconstructions of chromosomes and spindles in prometaphase. 5…”

Spindle Assembly and Chromosome Segregation Requires Central Spindle Proteins inDrosophilaOocytes

“…Similarly, another prominent central spindle component is the CPC, which is also required for acentrosomal spindle assembly (Colombié et al 2008;Radford et al 2012). Based on these and other studies, we and others have suggested that, in the absence of centrosomes, the central spindle has a critical role in organizing the microtubules and chromosome alignment (Jang et al 2005;Resnick et al 2006;Dumont and Desai 2012;Radford et al 2012). Thus, we have initiated the first comprehensive study of central spindle protein function in acentrosomal spindle assembly and chromosome segregation.…”

“…How a robust spindle assembles without guidance from the centrosomes is not well understood. While it is clear that the chromosomes can recruit microtubules and drive spindle assembly (Tseng et al 2010;Dumont and Desai 2012), how a bipolar spindle is organized and chromosomes make the correct attachments to microtubules is not understood.The Drosophila oocyte provides a genetically tractable system for the identification of genes involved in acentrosomal spindle assembly. Substantial evidence in Drosophila suggests that the chromosomes direct microtubule assembly, subsequent elongation of the spindle, and establishment of spindle bipolarity (Theurkauf and Hawley 1992;Matthies et al 1996;Doubilet and McKim 2007).…”

“…How a robust spindle assembles without guidance from the centrosomes is not well understood. While it is clear that the chromosomes can recruit microtubules and drive spindle assembly (Tseng et al 2010;Dumont and Desai 2012), how a bipolar spindle is organized and chromosomes make the correct attachments to microtubules is not understood.…”

“…This equatorial region is composed of antiparallel microtubules and is a structure that includes a plethora of proteins (Jang et al 2005). Assembling a central microtubule array may be a conserved mechanism to organize a bipolar spindle in the absence of centrosomes (Dumont and Desai 2012).…”