DDRGK1 (DDRGK domain-containing protein 1), also known as C20orf116, is a 314 amino acid secreted protein. DDRGK1 contains one PCI domain and is expressed as two isoforms produced by alternative splicing. The gene that encodes DDRGK1 maps to human chromosome 20, which represents about 2% of human DNA and consists of approximately 63 million bases and 600 genes. Chromosome 20 contains a region with numerous genes expressed in the epididymis, which are thought to be important for seminal production. The PRNP gene encoding the prion protein associated with spongiform encephalopathies, like Creutzfeldt-Jakob disease, is found on chromosome 20. Amyotrophic lateral sclerosis, spinal muscular atrophy, ring chromosome 20 epilepsy syndrome and Alagille syndrome are also associated with chromosome 20.