Sciatin: immunocytochemical localization of a myotrophic protein in chicken neural tissues

A mytotrophic protein (sciatin) purified from chicken sciatic nerves has "trophic" or "maintenance" effects on cultured muscle. We have elicited a specific antiserum against purified sciatin in rabbits. Using this antiserum, we investigated the distribution of sciatin in embryonic and adult chicken tissues by an unlabeled peroxidase-an-tiperoxidase method at the light microscopic level. The antiserum stained adult chicken neural tissues in situ and cultured embryonic chick neurons. Staining was intense in the cell bodies of spinal cord neurons and the axoplasm of sciatic nerves. These was reaction product seen in the outer margins of myelin sheaths that corresponded to the Schwann cell cytoplasm. Cerebral cortical neurons were weakly stained by the antiserum. No staining was apparent in oligodendrocytes or astrocytes. Nonneural tissues, such as skeletal, smooth and cardiac muscle, kidney, and liver, were also unstained by the antiserum. Cultured spinal cord neurons, cerebral cortical neurons, and sensory neurons were stained immunocytochemically by the antiserum. There was no reaction product seen in the glial cells that are usually present in neuronal cultures or cultured cells from liver, kidney, skeletal muscle, smooth muscle, and cardiac muscle. Our results thus show that the myotrophic protein is localized in neuronal perikarya and their processes in vivo as well as in vitro.