DIFFERENTIAL EXPRESSION OF TENASCIN SPLICING VARIANTS IN THE CHICK GIZZARD AND IN CELL-CULTURES

Tenascin is a large disulfide-linked hexameric extracellular matrix glycoprotein. It is a multidomain protein containing many repeated structural units such as heptad-, EGF-like-, and fibronectin type III repeats, as well as a homology to the globular domains of beta- and gamma-fibrinogen. In the chick embryo three major tenascin variants exist. They arise from one gene by alternative splicing of three of its 11 fibronectin type III repeats. Monoclonal antibodies against the alternatively spliced domains allowed us to study the expression of tenascin variants in tissue sections and in cell cultures. In the gizzard, the largest tenascin variant was only detected in the smooth muscle layer and the connective tissue below the epithelium of the villi, whereas the shortest tenascin variant was predominant in the tendons and the intramuscular connective tissue. Differential expression of tenascin variants was also obtained in cell cultures of chick embryo fibroblasts. Fetal calf serum equally stimulated the accumulation of all three tenascin variants, whereas after transformation with polyomavirus middle-T only the secretion of the largest tenascin variant was greatly enhanced.