Key regulator of kinetochore function during meiosis I: required both for mono-orientation of kinetochores on sister chromosomes and protection of centromeric cohesin from separase-mediated cleavage. Acts by facilitating kinetochore mono-orientation during meiosis I, when kinetochores on sister chromosomes face the same direction and are thus captured and pulled by spindle fibers from the same pole. Also required to prevent cleavage of cohesin at centromeres during meiosis I, possibly by acting as a regulator of the shugoshin-dependent protection pathway. Acts in collaboration with PLK1: required for PLK1 enrichment to kinetochores. Not required during meiosis II or mitosis. Interacts with CENPC. Interacts with PLK1; required for recruitment of PLK1 at kinetochores. Localizes at kinetochores in meiosis I but undetectable in meiosis II. Germ cell-specific. Expressed in both testis and ovary. Not expressed in other tissues. Appears at centromeres during the pachytene stage, when homologous chromosomes are synapsed. Peaks during diplotene stage, persists with gradual reduction until metaphase I, and disappears in anaphase I. Does not reappear on chromatin in meiosis II. Infertility due to defects in meiosis. Mice develop normally and show no visible phenotype but are completely infertile (both males and females) due to defects in meiotic chromosome segregation during meiosis I. Monooriented kinetochores split prematurely and sister chromosomes separate entirely before anaphase of meiosis II.