ARRDC1, ARRDC2 (which exists as multiple alternatively spliced isoforms), ARRDC4 and ARRDC5 are arrestin domain-containing proteins that are encoded by genes which map to human chromosomes 9, 15 and 19. Chromosome 9, on which the ARRDC1 gene is localized, contains 145 million base pairs and comprises 4% of the human genome, encoding nearly 900 genes. Hereditary hemorrhagic telangiectasia, which is characterized by harmful vascular defects, and Familial dysautonomia, are both associated with chromosome 9.