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CD4 homologues in Atlantic salmon
L J Moore1, J M Dijkstra, E O Koppang
1Department of Biology, University of Bergen, Bergen, Norway. lindsey.moore@bio.uib.no
Fish & Shellfish Immunology
|November 6, 2008
Summary
Atlantic salmon possess CD4-1 and CD4-2 genes, homologous to mammalian CD4, with distinct domain structures and conserved functional motifs. These genes show differential tissue expression alongside T cell markers.
Area of Science:
- Immunology
- Genomics
- Comparative Biology
Background:
- CD4 is a crucial co-receptor in mammalian T cell activation, interacting with the T cell receptor (TCR) and MHC II/peptide complex.
- Mammalian CD4 features four extracellular immunoglobulin-like (Ig-like) domains and binds p56lck in its cytoplasmic domain, initiating T cell signaling.
- Previous studies identified CD4-2 in rainbow trout, adjacent to CD4-1, with two extracellular domains.
Purpose of the Study:
- To identify and characterize CD4 homologues in Atlantic salmon (Salmo salar).
- To investigate the gene structure, sequence homology, and expression patterns of Atlantic salmon CD4 genes.
- To compare these findings with known CD4 genes in other vertebrates, particularly teleosts.
Main Methods:
- Southern blot analysis to determine gene copy number.
- Gene sequencing to analyze exon-intron structure and identify conserved motifs.
- Quantitative reverse transcription PCR (qRT-PCR) to assess tissue-specific gene expression.
- Bioinformatic analysis to compare sequence identity and similarity with other species.
Main Results:
- Atlantic salmon possess CD4-1 (four extracellular domains) and two CD4-2 subtypes (CD4-2a and CD4-2b, two extracellular domains).
- Southern blot revealed two copies of the CD4-1 gene in rainbow trout.
- Sequenced salmon CD4 genes exhibit typical CD4 traits, including exon-intron organization and a conserved Lck binding motif, despite low sequence identity to higher vertebrates.
- CD4-1 and CD4-2 genes show differential tissue expression patterns, correlating with other T cell markers like TCR and CD3.
Conclusions:
- Atlantic salmon possess distinct CD4-1 and CD4-2 genes with structural similarities to mammalian CD4, including conserved functional domains.
- The identified genes are homologous to mammalian CD4, suggesting conserved roles in teleost adaptive immunity.
- Differential gene expression indicates specialized functions and regulation of CD4-related immune responses in Atlantic salmon.
