Immunohistochemical Detection of Various Proteoglycans in the Extracellular Matrix of Zebra Mussels

Abstract

Mussels have been used as animal models for studying ecotoxicology, biomineralization, and bio-adhesion for many years. Despite a wealth of studies on their shell matrix and byssus proteins, few studies have focused on the extracellular matrix molecules in mussel soft tissues. Extracellular matrix molecules may play important roles in biomineralization, immune reaction, and tissue homeostasis. In the present study, extracellular matrix and mineralization-related molecules in zebra mussel soft tissue were immunolocalized using well-characterized monoclonal antibodies. Our results demonstrate specific immunolocalization for collagen IV, fibronectin, and keratan sulfate in hemocytes; collagen IV in peripheral nerves; and aggrecan, link protein, and collagen XVIII in foot tissue. Laminin, decorin, and osteonectin were also broadly immunolocalized in mussel soft tissues. The distributions of these extracellular matrix molecules in mussel tissues are in line with the cell-mediated shell mineralization hypothesis, providing evidence for the molecules involved in the peripheral nervous system and byssus formation, and explaining the conservation of extracellular matrix molecules during evolution. These results further contribute to establishing zebra mussels as an attractive animal model in biomedical research.