ZPBP1 (zona pellucida-binding protein 1) is a 351 amino acid gene product belonging to the zona pellucida-binding protein Sp38 family. ZPBP1 is a secreted protein believed to be involved in gamete interaction during fertilization. ZPBP1 is found on chromosome 7 which is about 158 milllion bases long, encodes over 1,000 genes and makes up about 5% of the human genome. Chromosome 7 has been linked to osteogenesis imperfecta, Pendred syndrome, lissencephaly, citrullinemia and Shwachman-Diamond syndrome. The deletion of a portion of the q arm of chromosome 7 is associated with Williams-Beuren syndrome, a condition characterized by mild mental retardation, an unusual comfort and friendliness with strangers and an elfin appearance. Deletions of portions of the q arm of chromosome 7 are also seen in a number of myeloid disorders including cases of acute myelogenous leukemia and myelodysplasia.