Required during meiosis for separation of sister chromatids and homologous chromosomes. Proteolytic cleavage of REC8 on chromosome arms by separin during anaphase I allows for homologous chromosome separation in meiosis I and cleavage of REC8 on centromeres during anaphase II allows for sister chromatid separation in meiosis II. Interacts (phosphorylated and unphosphorylated form) with SMC3. Interacts with SYCP3. Interacts (phosphorylated and unphosphorylated form) with SMC1B. Does not interact with SMC1A. Interacts with RAD51. Forms a complex with EWSR1, PRDM9, SYCP3 and SYCP1; complex formation is dependent of phosphorylated form of REC8 and requires PRDM9 bound to hotspot DNA; EWSR1 joins PRDM9 with the chromosomal axis through REC8 (PubMed:27932493). In meiotic chromosomes, localized along axial elements in prophase from the leptotene to diplotene stages. At later prophase stages, diakinesis and metaphase I, localized along interstitial axes of chromosomes including both centromere and arm regions. No longer detected in arm regions in anaphase I but persists on centromere regions until metaphase II. Expressed primarily in the gonads. In the testis, expressed in pachytene spermatocytes and in spermatids. Not expressed in spermatogonia or somatic cells. In the ovary, expressed only in oocytes. Low levels also detected in a number of somatic tissues including thymus, lung, liver, kidney and small intestine. Expressed from 2 weeks postpartum (at protein level). Phosphorylated. Mice display a high mortality rate, both during embryogenesis and after birth, germ cell failure and sterility. Mutant females exhibit ovarian dysgenesis and lack ovarian follicles at reproductive maturity. Affected males have small testes due to arrest of spermatogenesis during meiotic prophase I. Early chromosome pairing appears normal but synapsis occurs between sister chromatids rather than between homologous chromosomes. Belongs to the rad21 family.