OIP5 is a 229 amino acid nuclear protein that is required for chromosome segregation during mitosis. OIP5 exists as a homodimer but can also heterodimerize with FASP1 (FAPP1-associated protein 1). Essential for the recruitment of CENP-A (centromere autoantigen A) to centromeres, OIP5 localizes to centromeres of interphase cells during late anaphase and G1. The gene encoding OIP5 maps to human chromosome 15, which houses over 700 genes and comprises nearly 3% of the human genome. Angelman syndrome, Prader-Willi syndrome, Tay-Sachs disease and Marfan syndrome are all associated with defects in chromosome 15-localized genes.