CTDSPL2 (CTD (carboxy-terminal domain, RNA polymerase II, polypeptide A) small phosphatase like 2), also known as HSPC058 or HSPC129, is a 466 amino acid protein that contains one FCP1 homology domain and belongs to the CTDSPL2 family. Existing as two alternatively spliced isoforms, CTDSPL2 is thought to function as a phosphatase and is encoded by a gene that maps to human chromosome 15q15.3. Encoding more than 700 genes, chromosome 15 is made up of approximately 106 million base pairs and comprises about 3% of the human genome. Angelman syndrome, Prader-Willi syndrome, Tay-Sachs disease and Marfan syndrome are all associated with defects in chromosome 15-localized genes.