Distribution of testican expression in human brain

Testican is a putative extracellular heparan/ chondroitin sulfate proteogly can of unknown function that is expressed in a variety of human tissues at widely different levels but is most abundant in the brain. In mice, testica n mRNA has been detected only in brain and it is therefore likely to have a n important function in the central nervous system. RNA blot analysis revea ls the relative intensity of testican in various regions of the human brain . Levels of testican message are most pronounced in the thalamus, hippocamp us, occipital lobe, nucleus accumbens, temporal lobe, and caudate nucleus, with somewhat lower levels in the cerebral cortex, medulla oblongata, front al lobe, amygdala, putamen, spinal cord, substantia nigra, and cerebellum. In situ hybridization reveals the cellular distribution of the mRNA within these areas to be highest in neurons and in choroid plexus epithelium, and moderately lower in ependymal cells lining the ventricles and in vascular e ndothelial cells. Testican mRNA is not detected in oligodendrocytes or in m ost astrocytes. However, astrocytes in regions of reactive gliosis do expre ss testican mRNA. These findings, along with a cysteine-rich pattern simila rity to neurocan, brevican, versican, and other proteoglycans found in brai n, suggest that testican may be a part of the specialized extracellular mat rix of the brain.