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Proteolytic activity of separase is required for chiasma resolution during meiosis I in mouse oocytes. Rec8, the meiosis-specific alpha-kleisin subunit of cohesin, is a key target of separase in yeast. Is the equivalent protein also a target in mammals? We show here that separase cleaves mouse Rec8 at three positions in vitro but only when the latter is hyper-phosphorylated. Expression of a Rec8 variant (Rec8-N) that cannot be cleaved in vitro at these sites causes sterility in male mice. Their seminiferous tubules lack a normal complement of 2 C secondary spermatocytes and 1 C spermatids and contain instead a high proportion of cells with enlarged nuclei. Chromosome spreads reveal that Rec8-N expression has no effect in primary spermatocytes but produces secondary spermatocytes and spermatids with a 4 C DNA content, suggesting that the first and possibly also the second meiotic division is abolished. Expression of Rec8-N in oocytes causes chromosome segregation to be asynchronous and delays its completion by 2-3 hours during anaphase I, probably due to inefficient proteolysis of Rec8-N by separase. Despite this effect, chromosome segregation must be quite accurate as Rec8-N does not greatly reduce female fertility. Our data is consistent with the notion that Rec8 cleavage is important and probably crucial for the resolution of chiasmata in males and females.

Original publication

DOI

10.1242/jcs.035287

Type

Journal article

Journal

J Cell Sci

Publication Date

01/08/2009

Volume

122

Pages

2686 - 2698

Keywords

Animals, Blotting, Western, Cell Cycle Proteins, Chromosomal Proteins, Non-Histone, Chromosome Segregation, Chromosomes, Artificial, Bacterial, Endopeptidases, Female, Genes, myc, Infertility, Male, Male, Meiosis, Mice, Mice, Transgenic, Mutagenesis, Site-Directed, Nuclear Proteins, Oocytes, Peptide Fragments, Phosphoproteins, Protein Subunits, Separase, Spermatogenesis