CCDC158 (coiled-coil domain containing 158), also known as FLJ25770 or MGC35086, is a 1,113 amino acid protein expressed as three isoforms produced by alternative splicing events. CCDC158 is encoded by a gene mapping to human chromosome 4. Human chromosome 4 represents approximately 6% of the human genome and contains nearly 900 genes. Notably, the Huntingtin gene, which is found to encode an expanded glutamine tract in cases of Huntington's disease, is on chromosome 4. FGFR-3 is also encoded by a gene that is located on chromosome 4, and has been associated with thanatophoric dwarfism, achondroplasia, Muenke syndrome and bladder cancer. Chromosome 4 is also tied to Ellis-van Creveld syndrome, methylmalonic acidemia and polycystic kidney disease.