Answer: Glial fibrillary acidic protein (GFAP) is a protein that can be stained as a marker for brain injury.
Within cells, there are several different proteins that function as structural support. One such type are the intermediate filaments, which are called so due to them being larger than microfilaments but smaller than myosin. In glia such as astrocytes, these intermediate filaments are made up of glial fibrillary acidic protein, GFAP.
After a brain injury such as stroke, autoimmune response, trauma, or infection, astrocytes move towards the site of the damage. This is called astrogliosis (or reactive astrocytosis) and is important for recovery of the injured brain area. It is likened to the normal tissue scarring that occurs elsewhere in the body. For example, absence of the glial scar prevents the repair of the blood-brain barrier. On the other hand, the glial scar prevents neuroregeneration through the release of inhibitor signaling molecules.
GFAP staining is a common procedure performed in the research laboratory. GFAP itself is 52 kD.
Clinically, a GFAP stain may be performed on a piece of excised brain tumor tissue to determine if the cancer is derived from glial cells.