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First published online July 22, 2009
doi: 10.1242/10.1242/jcs.035287

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Role of cleavage by separase of the Rec8 kleisin subunit of cohesin during mammalian meiosis I

Nobuaki R. Kudo^1,2,*, Martin Anger^1,3,, Antoine H. F. M. Peters^1,4, Olaf Stemmann^5,, Hans-Christian Theussl¹, Wolfgang Helmhart^1,3, Hiromi Kudo^1,¶, Christa Heyting⁶ and Kim Nasmyth^1,3,*

¹ Research Institute of Molecular Pathology, A-1030 Vienna, Austria
² Institute of Reproductive and Developmental Biology, Imperial College London, London W12 0NN, UK
³ University of Oxford, Department of Biochemistry, Oxford OX1 3QU, UK
⁴ Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland
⁵ Department of Molecular Cell Biology, Max-Planck Institute of Biochemistry, D-82152 Martinsried, Germany
⁶ Molecular Genetics Group, Wageningen University, NL-6703 BD Wageningen, The Netherlands

^* Authors for correspondence (e-mails: n.kudo{at}imperial.ac.uk; kim.nasmyth{at}bioch.ox.ac.uk)

Accepted 28 April 2009

Proteolytic activity of separase is required for chiasma resolution during meiosis I in mouse oocytes. Rec8, the meiosis-specific -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.

Key words: Chromosome segregation, Cohesin, Meiosis, Oocyte maturation, Separase, Spermatogenesis

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