ABSTRACT
Faithful chromosome segregation during meiosis I depends upon the formation of connections between homologous chromosome pairs. For most chromosome pairs a connection is provided by crossovers. The crossover creates a link that allows the pair to attach to the meiotic spindle as a unit, such that at anaphase I, the partners will migrate away from one another. Recent studies have shown that some chromosome pairs that fail to experience crossovers become paired at their centromeres in meiotic prophase, and in some organisms, this pairing has been shown to promote proper segregation of the partners, later, at anaphase I. Centromere pairing is mediated by synaptonemal complex (SC) proteins that persist at the centromere when the SC disassembles. Here, using experiments in mouse and yeast model systems, we tested the role of shugoshin in promoting meiotic centromere pairing by protecting centromeric synaptonemal components from disassembly. The results show that shugoshin protects centromeric SC in meiotic prophase and also promotes the proper segregation in anaphase of partner chromosomes that are not joined by a crossover.