Expression of Gla‐rich protein (GRP) in newly developed cartilage‐derived cell cultures from sturgeon ( Acipenser naccarii )

Summary Sturgeons are representative of an ancient fish group, and present mainly an internal cartilaginous skeleton, with bone found essentially in the ganoid plaques forming the exogenous skeleton. Because of its archaic genetics, sturgeon represents an important model organism to understand the role of bone and cartilage‐related Gla proteins and determine if their molecular mechanisms of action were maintained throughout evolution. Of particular relevance is understanding the regulation, in sturgeon, of those proteins known to be involved in tissue mineralization in mammals, as well as unveiling the function of newly identified calcification‐related genes such as the one encoding the recently discovered Gla‐rich protein (GRP), thus contributing to understand the poor calcification observed in sturgeon endoskeleton. However, regulation of gene expression and promoter functional analysis of sturgeon cartilage and bone‐specific genes has been hampered by lack of suitable in vitro cell systems. We have recently developed the first sturgeon vertebra ( VAn2H ) and branchial arches ( BAAn1F ) derived cell cultures, and here we report their inability to mineralize their ECM under mineralizing culture conditions, as detected by von Kossa staining. Although a more extensive characterization of these systems is ongoing, our first data indicate that these cells represent a valuable tool for expression analysis of sturgeon bone and cartilage genes.