Tenascin: cDNA cloning and induction by TGF-beta.

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Tenascin is an extracellular matrix glycoprotein with a limited tissue distribution.
• Understanding the regulation of tenascin synthesis is crucial for comprehending extracellular matrix dynamics.

Purpose of the Study:

• To isolate cDNA clones encoding tenascin.
• To investigate the in vitro induction of tenascin synthesis by growth factors and serum.
• To compare the regulation of tenascin with fibronectin.

Main Methods:

• Isolation of tenascin cDNA clones from a chicken fibroblast expression library using specific antiserum.
• Confirmation of protein sequences through limited trypsin treatment and peptide analysis.
• Northern blot analysis to detect tenascin mRNA levels.
• In vitro induction experiments using fetal calf serum and transforming growth factor beta (TGF-beta).

Main Results:

• cDNA clones encoding tenascin were successfully isolated, with the largest clone detailing 632 amino acids, including a unique cysteine-rich region with 13 epidermal growth factor-like repeats.
• Northern blot analysis indicated the presence of 8- to 9-kb tenascin messages.
• Tenascin synthesis and secretion were induced in vitro by fetal calf serum and TGF-beta in chick embryo fibroblasts.
• TGF-beta treatment led to a 4-fold increase in tenascin secretion, preceded by an increase in tenascin mRNA.
• Differential regulation of tenascin and fibronectin accumulation was observed in response to fetal calf serum and TGF-beta, with tenascin showing a greater increase.

Conclusions:

• Tenascin gene expression is inducible in vitro by TGF-beta and fetal calf serum.
• TGF-beta significantly upregulates tenascin mRNA and protein synthesis in chick embryo fibroblasts.
• Tenascin and fibronectin exhibit distinct regulatory patterns in response to extracellular stimuli.