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Title: Molecular characterization and expression analysis of importin "a" family genes in rainbow trout

item MA, HAO - West Virginia University
item Rexroad, Caird
item YAO, JIANBO - West Virginia University

Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: 1/9/2010
Publication Date: 1/9/2010
Citation: Ma, H., Rexroad III, C.E., Yao, J. 2010. Molecular characterization and expression analysis of importin "a" family genes in rainbow trout. Plant and Animal Genome Conference.

Interpretive Summary:

Technical Abstract: The importin a/importin ß-mediated import pathway plays an essential role in the transport of proteins bearing nuclear localization signals (NLS) into the nucleus. Importin a serves to recognize the cargo proteins. In mammals, 7 importin a proteins (KPNA1 to 7) have been characterized and each importin a appears to have distinct NLS-binding specificities. In fish, the importin a gene family has not been characterized yet. The objectives of this study were to identify the importin a family genes in rainbow trout, and characterize the temporal expression patterns of importin a family gene mRNAs during rainbow trout ovarian development and early embryogenesis. Through database mining, we identified the cDNA sequences coding for rainbow trout orthologs of importin a1 (KPNA2), importin a3 (KPNA4), importin a4 (KPNA3), importin a6 (KPNA5), and importin a8 (KPNA7). To date, we have obtained the complete cDNAs for KPNA2 and KPNA7. The KPNA2 cDNA codes for a protein of 526 amino acids and the KPNA7 cDNA is predicted to encode a protein of 519 amino acids. Both proteins contain a conserved IBB domain and 7-8 ARM motifs, typical characteristics for importin a proteins. Tissue distribution analysis by RT-PCR revealed that while the mRNAs for KPNA2, KPNA3, KPNA4 and KPNA5 are ubiquitously expressed, the KPNA7 mRNA is specifically expressed in gonads and early embryos. Further expression analysis showed that the transcripts for KPNA3, KPNA4 and KPNA5 are highly abundant in the early pre-vitellogenic stage ovary, while the KPNA7 mRNA is abundantly present in late vitellogenic stage ovary as well as in unfertilized oocytes and early stage embryos (day 1 to day 3), but barely detectable in embryos after day 5. Collectively, these results demonstrate that transcripts for different rainbow trout KPNA proteins are present at differing levels at specific stages of vitellogenesis and KPNA7 is a maternally expressed gene, which may play an important role in the transport of essential nuclear factors required for initiation of transcription in early embryos before embryonic genome activation.