Selective expression of the Met/HGF receptor in human central nervous system microglia.

The c-MET proto-oncogene encodes the tyrosine kinase receptor for hepatocyte growth factor (HGF), also known as scatter factor, a powerful mitogen and motility factor for epithelial cells. We now show that the two previously described forms of the Met/HGF receptor, the intact p190MET and the truncated p140MET, are expressed in physiological conditions in the human central nervous system (CNS). The receptors were identified by Western blot analysis with monoclonal antibodies directed against different epitopes. By immunohistochemical staining the Met/HGF receptor was found to be expressed in a homogeneous cell population, equally distributed between the grey and the white matter, showing morphological features and immunochemical markers specific for the resident microglial cells. These data suggest a possible role for the c-MET proto-oncogene and HGF in microglial reactions to CNS injuries.