Molecular cloning and characterization of the matricellular protein Sparc/osteonectin in flatfish, Scophthalmus maximus, and its developmental stage-dependent transcriptional regulation during metamorphosis

• Identification, isolation and molecular characterization of Sparc in turbot.
• Sparc protein shows a highly conserved structure across vertebrates.
• Sparc displays a dynamic stage-dependent expression during turbot post-embryonic development.
• Sparc expression is specifically upregulated during flatfish metamorphosis.
• Transcriptional regulation of sparc during turbot metamorphosis is ambient temperature-independent.

SPARC/osteonectin is a multifunctional matricellular glycoprotein, which is expressed in embryonic and adult tissues that undergo active proliferation and dynamic morphogenesis. Recent studies indicate that Sparc expression appears early in development, although its function and regulation during development are largely unknown. In this report, we describe the isolation, characterization, post-embryonic developmental expression and environmental thermal regulation of sparc in turbot. The full-length turbot sparc cDNA contains 930 bp and encodes a protein of 310 amino acids, which shares 77, 75 and 80% identity with human, frog and zebrafish, respectively. Results of whole-mount in situ hybridization reveal a dynamic expression profile during post-embryonic turbot development. Sparc is expressed differentially in the cranioencephalic region; mainly in jaws, branchial arches, fin folds and rays of caudal, dorsal and anal fins. Furthermore, ontogenetic studies demonstrated that Sparc gene expression is dynamically regulated during post-embryonic turbot development, with high expression during stage-specific post-embryonic remodeling. Additionally, the effect of thermal environmental conditions on turbot development and on ontogenetic sparc expression was evaluated.