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Expression of SPARC/osteonectin in tissues of bony and cartilaginous vertebrates
M Ringuette1, S Damjanovski, D Wheeler
1Department of Zoology, University of Toronto, Ont., Canada.
Abstract:
To explore the biological functions of SPARC (secreted protein, acidic, rich in cysteine), a Ca(2+)-binding extracellular glycoprotein, we have examined its expression in an evolutionary diverse group of organisms. Similar patterns of SPARC mRNA expression were observed in adult mouse and rat tissues. SPARC transcripts represented 0.0002-0.0025% of the total RNA found in calvarium, lung, brain, and heart, whereas relatively low levels of SPARC RNA were detected in liver and kidney. Within nonmuscular tissues, a statistically significant correlation was observed between the tissue distribution of SPARC and cytoskeletal actin transcripts. Southern blot analysis revealed SPARC as a low or single-copy gene in an evolutionary diverse group of vertebrates. No hybridization signal was observed with the invertebrates examined. The tissue distribution of SPARC transcripts in the vertebrates examined was similar, except for sea lamprey and sea skate, two vertebrates that do not form mineralized bone. These data suggest that SPARC has multiple functions in mineralized and nonmineralized tissues of vertebrates.
Insights
Secreted protein, acidic, rich in cysteine (SPARC) is a Ca(2+)-binding glycoprotein. Its expression patterns in vertebrates suggest diverse roles in both mineralized and nonmineralized tissues.
Area of Science:
- Biochemistry
- Molecular Biology
- Evolutionary Biology
Background:
- SPARC (secreted protein, acidic, rich in cysteine) is a Ca(2+)-binding extracellular glycoprotein.
- Understanding its biological functions requires examining its evolutionary conservation and tissue distribution.
Purpose of the Study:
- To investigate the biological functions of SPARC.
- To examine SPARC expression across a diverse range of organisms.
- To determine the evolutionary conservation of the SPARC gene.
Main Methods:
- Analysis of SPARC mRNA expression patterns in adult mouse and rat tissues using quantitative methods.
- Southern blot analysis to assess SPARC gene copy number in vertebrates and invertebrates.
- Comparative analysis of SPARC transcript distribution across different species.
Main Results:
- SPARC mRNA expression showed similar patterns in adult mouse and rat tissues, with varying levels across different organs.
- A significant correlation was found between SPARC and cytoskeletal actin transcript distribution in nonmuscular tissues.
- SPARC was identified as a low or single-copy gene in vertebrates but was absent in invertebrates.
- SPARC transcript distribution was conserved in vertebrates, with notable differences in species lacking mineralized bone.
Conclusions:
- SPARC plays multiple biological roles in both mineralized and nonmineralized vertebrate tissues.
- The evolutionary conservation of SPARC suggests fundamental functions across vertebrate species.
- SPARC's association with cytoskeletal actin may indicate involvement in cellular structure and function.