Investigating the role of Cdc14 in the regulation of the meiosis I to meiosis II transition

Abstract

Meiosis is a specialized cell division that produces haploid gametes from a diploid progenitor cell. It consists of one round of DNA replication followed by two consecutive rounds of chromosome segregation. Homologous chromosomes segregate in meiosis I and sister chromatids segregate in meiosis II. Failure to correctly regulate meiosis can result in aneuploidy, where daughter cells inherit an incorrect number of chromosomes. Aneuploidy is usually poorly tolerated in eukaryotes, and is associated with infertility, miscarriages and birth defects. At the meiosis I to meiosis II transition, DNA replication does not occur between chromosome segregation steps despite the need for Spindle Pole Bodies (SPBs) to be re-licensed in order to build meiosis II spindles. The mechanisms that make this distinction are not yet known. In budding yeast, the protein phosphatase Cdc14 is essential for the progression of cells into meiosis II. Cdc14 is sequestered for the majority of the cell cycle in the nucleolus by the inhibitor Cfi1/Net, and is only released in anaphase. We have observed Cdc14 localizing to and interacting with SPB components when nucleolar sequestration is inhibited. Through fluorescence microscopy and EM analysis, we have determined that Cdc14 is required for the re-duplication of SPBs after meiosis I. Our data implies a role for Cdc14 in the phospho-regulation of SPB half-bridge component Sfi1. Cdc14 is therefore essential for the relicensing of SPB duplication, a crucial step necessary to ensure accurate chromosome segregation in meiosis.