Biological Significance: S-100 is a low molecular weight, cytoplasmic, calcium binding protein. It is traditionally found in the brain, heart and muscle tissue. S-100 has two subunits (alpha-chain and beta-chain) and exists in several different forms. The alpha-alpha homodimer is referred to in literature as either the S-100αα or S-100aa. S-100 protein is expressed from the beginning of lipidogenesis and may act as a factor regulating lipid storage and body fat formation. It can be used as a reliable biochemical marker of human fat cell differentiation and for distinguishing them from the mesenchymal and the fibroblast cells in the human embryonal subcutis
