Identification of upregulated genes in the thymus of spontaneously hypertensive rats by cDNA representational difference analysis

Objective: To investigate molecular events associated with thymus dysfunction in the spontaneously hypertensive rat (SHR), we analysed the difference in gene expression of the thymus between SHR and Wistar-Kyoto (WKY) rats. Methods: cDNA representational difference analysis (cDNA-RDA) was applied to compare the gene expression in the thymus between SHR and WKY. The difference products of cDNA-RDA were cloned into pBluescript SK (+) for differential screening. The positive clones were sequenced, and the sequences were analysed using the BLAST program for the homology search. Northern blot analysis was used to confirm the results of differential screening. Results: The results of differential screening showed that eight genes were over- expressed in the thymus of SHR. Comparison of eight sequences against the databases identified four known and four novel genes. The known genes included cathepsin B, AT1-46, cytochrome C oxidase subunit I and metastasis suppressor homolog (KAI1). Two of the novel genes are members of immunoglobulin superfamily genes, and the rest of the novel genes have no significant homology to non-redundant GenBank +EMBL +DDBJ +PDB. By Northern blot hybridization, cathepsin B and clone 7 (GenBank accession AF106623) genes were confirmed to be overexpressed in the SHR thymus. Conclusion: cDNA- RDA combined with differential screening can be used to detect easily the differentially regulated genes in two comparable tissues. The eight isolated genes are good clues toward understanding the development and function of SHR thymus.