FSD2 is a 749 amino acid protein containing one B30.2/SPRY domain and two fibronectin type-III domains. The gene encoding FSD2 maps to human chromosome 15q25.2. Encoding more than 700 genes, chromosome 15 is made up of approximately 106 million base pairs and consists of about 3% of the human genome. Angelman and Prader-Willi syndromes are associated with loss of function or deletion of genes in the 15q11-q13 region. In the case of Angelman syndrome, this loss is due to inactivity of the maternal 15q11-q13 encoded UBE3A gene in the brain by either chromosomal deletion or mutation. Prader-Willi syndrome, Tay-Sachs disease and Marfan syndrome are also associated with chromosome 15.