OCIAD2 (OCIA domain containing 2) is a 154 amino acid protein that localizes to endosomes and contains one OCIA domain. OCIAD2 exists as multiple alternative spliced isoforms and is encoded by a gene which localizes to human chromosome 4. Representing approximately 6% of the human genome, chromosome 4 contains nearly 900 genes, one of which is the Huntingtin gene, which is found to encode an expanded glutamine tract in cases of Huntington's disease.