MSP, a trypsin-like serine protease, is abundantly expressed in the human nervous system

The goal of the present investigation was to determine the regional and cel lular specific expression patterns of the newly identified serine protease, myelencephalon-specific protease (MSP), in the adult human brain (Scarisbr ick et al. [1997b] J. Neurosci. 17:8156-8168). To assess the potential scop e of MSP activity, Northern blot techniques were used to determine the rela tive abundance of MSP mRNA in 16 different adult human brain regions, and i n the brain and peripheral tissues of the midgestation human fetus. The reg ional and temporal specific expression patterns of MSP mRNA were directly c ompared with those of tissue plasminogen activator (tPA), a serine protease strongly implicated in the development, ongoing plasticity, and response o f the nervous system to injury and disease. mRNA encoding each protease was distributed widely throughout the normal adult human central nervous syste m (CNS), but the expression of each was only partially overlapping. Additio nally, compared with tPA, MSP exhibited a more restricted distribution and delayed developmental onset. By immunohistochemical localization, MSP was p resent at moderate to high levels in neurons and oligodendroglia of the adu lt human brain, at a level closely resembling the relative abundance indica ted by Northern blot. MSP was most abundantly expressed in the spinal cord, hippocampus, substantia nigra, and basal ganglia. The robust expression of MSP in clinically significant regions of the adult human CNS indicates tha t further study of this protease in terms of both normal brain physiology a nd neurodegenerative disorders is warranted.