TETRANECTIN IS A NOVEL MARKER FOR MYOGENESIS DURING EMBRYONIC-DEVELOPMENT, MUSCLE REGENERATION, AND MUSCLE-CELL DIFFERENTIATION IN-VITRO

Tetranectin, a plasminogen-binding protein with a C-type lectin domain , is found in both serum and the extracellular matrix. In the present study we report that tetranectin is closely associated with myogenesis during embryonic development, skeletal muscle regeneration, and muscl e cell differentiation in vitro. We find that tetranectin expression c oincides with muscle differentiation and maturation in the second half of gestation and further that tetranectin is enriched at the myotendi nous and myofascial junctions. The tetranectin immunostaining declines after birth and no immunostaining is observed in normal adult muscle. However, during skeletal muscle regeneration induced by the intramusc ular injection of the myotoxic anesthetic Marcaine, myoblasts, myotube s, and the stumps of damaged myofibers exhibit intense tetranectin imm unostaining. Tetranectin is also present in regenerating muscle cells in dystrophic mdx mice. Murine C2C12 myogenic cells and pluripotent em bryonic stem cells can undergo muscle cell differentiation in vitro. T etranectin is not expressed in the undifferentiated myogenic cells, bu t during the progression of muscle differentiation, tetranectin mRNA i s induced, and both cytoplasmic and cell surface tetranectin immunosta ining become apparent. Finally, we demonstrate that while tetranectin mRNA is translated to a similar degree in developing limbs and lung, t he protein does not seem to be tissue associated in the lung as it is in the limbs. This indicates that in some tissues, such as the limbs, tetranectin may function locally, whereas in other tissues, such as th e lung, tetranectin production may be destined for body fluids. In sum mary, these results suggest that tetranectin is a matricellular protei n and plays a role in myogenesis. (C) 1998 Academic Press.