Plectin in the human central nervous system: predominant expression at pia/glia and endothelia/glia interfaces

Plectin is a high molecular weight protein that serves as a versatile cytoskeletal cross-linker molecule. Mutations of the human plectin gene have recently been identified to cause the autosomal recessive disorder epidermolysis bullosa simplex with muscular dystrophy (EBS-MD). A subgroup of EBS-MD patients display signs of a neurodegenerative disorder suggesting that the expression of defective plectin may also interfere with the structural and functional integrity of the human central nervous system. However, the expression pattern of plectin in the human brain is still unknown. We therefore analyzed the immunohistochemical distribution of plectin in normal hippocampal specimens obtained at autopsy and in neocortical and hippocampal tissue of patients who had undergone epilepsy surgery. In general, plectin-immunoreactive cells were identified as capillary endothelia and astrocytes. A striking feature seen in all specimens was the accentuated plectin immunoreactivity of astrocytic end feet abutting on blood vessels and on the pial surface. Furthermore, the analysis of hippocampal tissue of epilepsy patients with Ammon's horn sclerosis (AHS) revealed a strong plectin labeling of reactive astrocytes. The latter finding suggests that the up-regulation of plectin, which parallels the increase of glial fibrillary acidic protein, may be a general feature of reactive astroglia. The predominant expression of plectin at pia/glia and endothelia/glia interfaces in the human brain indicates that plectin may have an integral role in the structural organization of the blood-brain barrier and the leptomeninges.