S100 comprises 19 members of Ca2+ binding proteins with low molecular weight between 9 kDa to 13 kDa. The S100 falmily proteins have been implicated to regulate protein phosphorylation, cell proliferation and differentiation in the Ca2+-dependent way. S100B is abundant in glial cells of the central and peripheral nervous system, in melanocytes, chondrocytes, and adipocytes. Chromosomal rearrangements and altered expression of this gene have been implicated in several neurological, neoplastic, and other types of diseases, including Alzheimer's disease, Down's syndrome, epilepsy, amyotrophic lateral sclerosis, melanoma, and type I diabetes. It is a useful marker for the identification of melanoma and various nervous system tumors.