CELLULAR-ORIGINS OF TENASCIN IN THE DEVELOPING NERVOUS-SYSTEM

We have used in situ hybridization and reverse transcriptase polymeras e chain reaction (PCR) to study the origins of the extracellular matri x glycoprotein tenascin during the development of the central and peri pheral nervous systems. Previous studies have shown that neural crest cells migrate along pathways that are lined with tenascin. In situ hyb ridization, PCR, and western blotting reveal that these cells themselv es are a major source of tenascin both in vitro and in the embryo. Thu s, tenascin is probably not acting as a guidance molecule but is more likely to be promoting neural crest cell motility in a more general wa y. Similarly, subpopulations of proliferating and migrating glia make tenascin in the developing central nervous system, as do the radial gl ia that are used as a substratum for migrating neuronal cell bodies to be expressed in the cerebellum by Golgi epithelial cells. This expres sion, as well as the expression of tenascin in connective tissue, indi cates that this molecule may also be playing a role in regulating diff erentiation. Finally, the distribution of tenascin transcripts in the developing brain and spinal cord is similar to the distribution of mRN As encoding receptors for platelet-derived growth factor-AA and basic fibroblast growth factor. In vitro studies indicate that both of these factors are potential regulators of tenascin expression.