Sporulation in diploid cells homozygous for the cyr1-2 mutation of the yeast Saccharomyces cerevisiae was examined. This mutation causes a defect in adenylate cyclase and temperature-sensitive arrest in the G1 phase of the mitotic cell cycle. The cyr1-2/cyr1-2 diploid cells were able to initiate meiotic divisions, but produced predominantly two-spored asci at the restrictive temperature. Temper...

Meiotic resumption (G2/M transition) and progression through meiosis I (MI) are two key stages for producing fertilization-competent eggs. Here, we report that CenpH, a component of the kinetochore inner plate, is responsible for G2/M transition in meiotic mouse oocytes. Depletion of CenpH by morpholino injection decreased cyclin B1 levels, resulting in attenuation of maturation-promoting facto...

The tandem Tudor-like domain-containing protein Spindlin1 has been reported to be a meiotic spindle-associated protein. Here we report that Spindlin1 is not associated with the spindle in mouse embryonic fibroblast cells during mitotic divisions. In interphase cells, Spindlin1 specifically localizes to the nucleoli. Moreover, Spindlin1 is a histone methylation effector protein that specifically...

Meiotic behavior and pollen fertility were analysed in five Epimedium species: Epimedium chlorandrum, Epimedium acuminatum, Epimedium davidii, Epimedium ecalcaratum and Epimedium pubescens. Chromosome numbers for five species were 2n = 2x = 12. All examined species displayed stable meiotic process and high pollen fertility (>76.67%). Meiotic abnormality partially affected pollen fertility. At m...

MEI-1, the catalytic subunit of the Caenorhabditis elegans "katanin" microtubule-severing complex, is required for meiotic spindle formation. However, MEI-1 must be inactivated after the completion of meiosis to allow formation of the first mitotic spindle. Recent work demonstrated that post-meiotic MEI-1 undergoes ubiquitin-dependent degradation mediated by two independent pathways. Here we de...

Bipolar spindles must separate chromosomes by the appropriate distance during cell division, but mechanisms determining spindle length are poorly understood. Based on a 2D model of meiotic spindle assembly, we predicted that higher localized microtubule (MT) depolymerization rates could generate the shorter spindles observed in egg extracts of X. tropicalis compared to X. laevis. We found that ...

In meiosis I, homologous chromosomes pair and then attach to the spindle so that the homologs can be pulled apart at anaphase I. The segregation of homologs before pairing would be catastrophic. We describe two mechanisms that prevent this. First, in early meiosis, Ipl1, the budding yeast homolog of the mammalian Aurora B kinase, triggers shedding of a kinetochore protein, preventing microtubul...

We have previously described the gene mei-1, which encodes an essential component of the Caenorhabditis elegans meiotic spindle. When ectopically expressed after the completion of meiosis, mei-1 protein disrupts the function of the mitotic cleavage spindles. In this article, we describe the cloning and the further genetic characterization of mel-26, a postmeiotic negative regulator of mei-1. me...

The Drosophila gene ald encodes the fly ortholog of mps1, a conserved kinetochore-associated protein kinase required for the meiotic and mitotic spindle assembly checkpoints. Using live imaging, we demonstrate that oocytes lacking Ald/Mps1 (hereafter referred to as Ald) protein enter anaphase I immediately upon completing spindle formation, in a fashion that does not allow sufficient time for n...

NuMA is a well-characterized organizer of the mitotic spindle, which is believed to play a structural role in interphase nucleus. We studied the expression of NuMA in rat seminiferous epithelium in detail. Different stages of the cycle of the seminiferous epithelium were identified using transillumination. Corresponding areas were microdissected and analysed using immunofluorescence, immunohist...