Extracellular Matrix Components in Bivalvia: Shell and ECM Components in Developmental and Adult Tissues

Abstract

The Extracellular matrix (ECM) is a vital trigger of molecular events in development, homeostasis, cell phenotypes, and evolution. Annotated genome databases and their comparative analyses enable the assessment of the most conservative representation of the ECM components among the Metazoa. Bivalves are widely distributed animals present in various ecological niches. They have shells, indirect developmental life cycles, and highly diverse adaptations and habitat reflected by their ECM repertoire. Only recently, researchers began to characterize the conservation among invertebrates and unique species-specific ECM components involved in biomineralization, development, and cell-cell communications. Here, I discuss the most recent data for the dynamic expression of ECM proteins based on transcriptome data during larval oyster development and in adult organs. Using developmental and cell biology approaches along with confocal microscopy, I showed the expression of certain ECM components in the larvae, adult tissues, and cell cultures. A similar methodology is required to understand the molecular mechanisms and dynamic ECM expression in organisms with very complex life cycles, metamorphosis, indirect development via adaptive larvae, and biomineralization during development.

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

“…In the mineralization of zebra mussels, so far, no specific mineralization cells, such as osteoclasts or osteoblasts, have been reported, but the mantle cells seem to possess some of the capabilities of these vertebrate bone cells. The broadly expressed pattern of SPARC in zebra mussel soft tissues was also consistent with the report of gene expression of collagen IV and SPARC in oyster tissues [8]. SPARC expression in mussels might regulate the formation and growth of mineral crystals, cell-cell and cell-matrix interactions, and inhibition of cell migration [60], which is also important for immune responses.…”

“…Biomineralization mechanisms of shells, bio-adhesive molecules in byssus, and bio-indicator usages for the detection of toxic chemicals [6,7] have all been of particular interest. However, apart from the shell and byssus, few studies have dealt with the extracellular matrix of the soft body tissues within bivalves [8].…”

Independent adoptions of a set of proteins found in the matrix of the mineralized shell-like eggcase of Argonaut octopuses

“…Many of these proteins are characterized by composition of both RLCDs and highly conserved enzymes, such as peroxidases, CAs, chitinases, acidic calcium-binding proteins, and protease inhibitors (Marie et al 2012). Other SMPs include acidic proteins involved in CaCO 3 crystallization, chitin-binding proteins, and ECM-related proteins (Pif, BMSP, EGF-ZP, SPARC) (Dyachuk, 2018; Feng et al 2017).…”

“…Interestingly, many of these proteins mostly contain well-characterized domains (repetitive low-complexity domains (RLCDs), peroxidases, carbonic anhydrases (CAs), chitinases, acidic calcium-binding proteins, and protease inhibitors) and thus are homologs of some non-shell matrix known proteins (Marie et al 2012). Other SMPs include acidic proteins probably involved in CaCO3 crystallization, such as Chitin-binding proteins and ECM-related proteins (Pif, BMSP, EGF-ZP, SPARC) (Dyachuk 2018, Feng et al 2017). The finding of highly conserved domains across the Conchiferanss indicates that SMPs have existed as ancestral genes for a long time (Kocot et al 2016; Setiamarga et al 2020).…”