SCFD2 is a 684 amino acid protein suggested to play a role in protein transport. Existing as two alternatively spliced isoforms, SCFD2 is a member of the STXBP/unc-18/SEC1 family and is encoded by a gene that maps to human chromosome 4q12. 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 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.