[SPO11: an activity that promotes DNA breaks required for meiosis]

Recombination between homologous chromosomes during meiosis is an essential process, which mechanistical function is to ensure the reductional segregation of chromosomes at the first meiotic division. SPO11, one of the key genes directly involved in this process, has been at the origin of considerable interest for the past five years, for several reasons. First, Spo11 is responsible for the initiation of meiotic recombination through the formation of DNA double-strand breaks by a type II DNA topoisomerase-like activity. Moreover, Spo11, and its function, have been conserved through evolution, from yeasts to human, as demonstrated by the identification of members of the Spo11 protein family and the analyses of corresponding mutants. Indeed, for every eukaryote that has been tested, spo11 mutants are deficient for meiotic recombination and are partially or completely sterile. Depending on the species, this reduced fertility reflects either a defect in chromosome segregation, or an arrest response in germ cell differentiation. Similarities and differences from species to species uncover a complex set of regulations that coordinate recombination with other events of meiotic prophase, such as chromosome pairing and meiotic cell cycle.