Structure of the meiotic spindle T he meiotic spindle is made up of shorter microtubules than previously believed, suggest results from Ge Yang, Gaudenz Danuser (Scripps Research Institute, La Jolla, CA), Ben Houghtaling, Tarun Kapoor (Rockefeller University, New York, NY), and colleagues. Current models of the spindle, as a bipolar array of overlapping fi laments extending from opposite spindl...

Polo-like kinase 1 (PLK1) orchestrates multiple events of cell division. Although PLK1 function has been intensively studied in centriole-containing and rapidly cycling somatic cells, much less is known about its function in the meiotic divisions of mammalian oocytes, which arrest for a long period of time in prophase before meiotic resumption and lack centrioles for spindle assembly. Here, usi...

in human fertilization, the sperm centrosome nucleates a radial array of microtubules called the sperm aster. the sperm aster is responsible for apposition of male and female pronuclei, and later gives rise to the first meiotic spindle. the objective of this study was to determine microtubule assembly and chromatin configuration in rabbit oocytes following intracytoplasmic injection with human ...

The meiotic spindles of animal eggs move to extremely asymmetric positions, close to the cell cortex. A recent paper has identified a motor complex that may move the meiotic spindle toward the cortex in Caenorhabditis elegans eggs.

High levels of mos protooncogene product are expressed during oocyte meiotic maturation and Mos has been implicated in formation of the spindle and spindle pole. Here, we show that in Swiss 3T3 cells with 4N DNA content, high levels of Mos lead to the production of binucleated cells. The Swiss 3T3 cells in mitosis, before binucleation occurs, are anastral and the spindle poles are juxtaposed to...

P21-activated kinase 1 (PAK1), an effector of Rho GTPase Rac 1 and Cdc42, is required for mitotic progression. However, its functions in meiosis are unclear. In the present study, we examined the expression, localization and function of PAK1 during mouse oocyte meiotic maturation and found that PAK1 was mainly associated with the meiotic spindle microtubules. Taxol treatment resulted in localiz...

Aneuploidy in human eggs is the leading cause of pregnancy loss and several genetic disorders such as Down syndrome. Most aneuploidy results from chromosome segregation errors during the meiotic divisions of an oocyte, the egg's progenitor cell. The basis for particularly error-prone chromosome segregation in human oocytes is not known. We analyzed meiosis in more than 100 live human oocytes an...

Background: In vitro maturation (IVM) is a promising treatment option for certain infertile women. Nowadays, with the aid of the Polscope, it has become possible to evaluate zona pellucida (ZP) and spindle as parameters of oocyte quality. The goal was to investigate the relationship between the presence of the meiotic spindle and ZP birefringence with morphology of the in vivo and in vitro matu...

The Drosophila microtubule motor protein, nonclaret disjunctional (ncd), is required for proper chromosome distribution in meiosis and mitosis. We have examined the meiotic and mitotic divisions in wild-type Drosophila oocytes and early embryos, and the effects of three ncd mutants (cand, ncd and ncdD) on spindle structure and chromosome movement. The ncd mutants cause abnormalities in spindle ...

Meiotic chromosome segregation occurs in Drosophila oocytes on an acentrosomal spindle, which raises interesting questions regarding spindle assembly and function. One is how to organize a bipolar spindle without microtubule organizing centers at the poles. Another question is how to orient the chromosomes without kinetochore capture of microtubules that grow from the poles. We have characteriz...