IN-SITU LOCALIZATION OF TENASCIN MESSENGER-RNA IN DEVELOPING MOUSE TEETH

Tenascin is a large extracellular-matrix glycoprotein found in develop ing connective tissue. A cDNA probe to mouse tenascin, mTN2, was used to determine the cellular origins of this molecule in the murine tooth germ by in situ hybridization. At embryonic day 19, a hybridization s ignal significantly greater than background was detected with mTN2 in the subodontoblastic layer of the dental mesenchyme and in the inner e namel epithelium of the enamel organ. At postnatal day 1, a signal was detected over pre-odontoblasts and the strata intermedium and externu m. No tenascin mRNA was detected in odontoblasts or the stellate retic ulum at either age, and hybridization in ameloblasts was not significa ntly greater than background at postnatal day 1. Thus, much of the ten ascin found throughout developing teeth appears to be synthesized by p re-odontoblasts and the inner enamel epithelium, the two populations o f cells destined to generate mineralized matrix.