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Characterization and expression of a gene encoding a 30.6-kDa Strongylocentrotus purpuratus spicule matrix protein
N C George1, C E Killian, F H Wilt
1Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Abstract:
We describe here the isolation and characterization of several cDNA clones that encode a single 30.6-kDa Strongylocentrotus purpuratus spicule matrix protein designated SM30. The clones were isolated by screening a lambda gt11 cDNA library with a rabbit polyclonal antiserum raised against S. purpuratus total spicule matrix proteins. DNA sequencing reveals that the SM30 protein is acidic. RNA blot analysis shows that the cDNAs hybridize to a single 1.8-kb transcript and that there is a sharp increase in the SM30 transcript levels at middle to late mesenchyme blastula stage. SM30 transcript levels remain high through the 3-day pluteus stage. In situ hybridization analysis indicates that, within the embryo, SM30 transcript accumulation is restricted to the primary mesenchyme cells. Quantitations of SM30 transcript levels show that by the prism stage there are about 29,000 SM30 transcripts present per embryo, which averages to approximately 480 transcripts per primary mesenchyme cell. Additionally, RNA blot analysis of total RNA isolated from adult tissues shows that SM30 mRNA accumulates exclusively in mineralized tissues. These findings taken together strongly suggest that the gene corresponding to the SM30 cDNAs does in fact encode a spicule matrix protein.
Insights
Researchers isolated and characterized SM30, a spicule matrix protein from Strongylocentrotus purpuratus. This protein is crucial for skeletal development, with its transcript levels increasing significantly during embryonic stages and accumulating in mineralized tissues.
Area of Science:
- Developmental Biology
- Molecular Biology
- Marine Biology
Background:
- The spicule matrix is essential for skeletal formation in sea urchins.
- Understanding the proteins involved in biomineralization is key to developmental studies.
Purpose of the Study:
- To isolate and characterize cDNA clones encoding a specific spicule matrix protein, SM30, from Strongylocentrotus purpuratus.
- To investigate the expression patterns and localization of the SM30 protein during sea urchin development.
Main Methods:
- Screening a lambda gt11 cDNA library using specific antibodies.
- DNA sequencing to determine protein characteristics.
- RNA blot analysis to assess transcript levels and size.
- In situ hybridization to localize transcript accumulation within the embryo.
Main Results:
- Several cDNA clones encoding a 30.6-kDa Strongylocentrotus purpuratus spicule matrix protein (SM30) were isolated and characterized.
- SM30 protein was found to be acidic, with its cDNA hybridizing to a single 1.8-kb transcript.
- SM30 transcript levels showed a sharp increase during the middle to late mesenchyme blastula stage and remained high through the pluteus stage.
- Transcript accumulation was localized to primary mesenchyme cells in the embryo.
- SM30 mRNA was found to accumulate exclusively in mineralized tissues of adult sea urchins.
Conclusions:
- The findings strongly suggest that the SM30 cDNAs encode a spicule matrix protein.
- SM30 plays a significant role in the biomineralization process during sea urchin development.
- The temporal and spatial expression patterns of SM30 indicate its specific function in skeletal element formation.