Fibroblasts can express glial fibrillary acidic protein (GFAP) in vivo

Neuropathologists use anti-glial fibrillary acidic protein (GFAP) antibodie s as specific markers for glial cells, and neurobiologists use GFAP for tar geting transgenes to glial cells. Since GFAP has also been detected in non- glial cells, we systematically analyzed GFAP expression in human and murine non-CNS tissues using a panel of anti-GFAP antibodies. In human tissues we confirm previously observed GFAP expression in Schwann cells, myoepithelia l cells, and chondrocytes, and show for the first time GFAP expression in f ibroblasts of epiglottic and auricular perichondrium, ligamentum flavum. an d cardiac valves. In mice we show GFAP expression in Schwann cells, bone ma rrow stromal cells, chondrocytes, and in fibroblasts of dura mater, skull a nd spinal perichondrium, and periosteum connective stroma of oral cavity, d ental pulp, and cardiac valves. Anti-GFAP immunoblotting of human non-CNS t issues reveals protein bands with a molecular mass ranging between approxim ate to 35 and approximate to 42 kDa. In GFAP-v-src transgenic mice, whose o ncogenic v-src transgene transforms GFAP expressing cells, non-CNS tumors o riginate from fibroblasts. We conclude that human and murine fibroblasts ca n express GFAP in vivo. The somatic distribution of GFAP expressing fibrobl asts indicates origin from the neural crest. Development of non-CNS tumors from fibroblasts in GFAP-v-src mice functionally confirms GFAP expression i n these cells.