Channel catfish CD8α and CD8β co-receptors: characterization, expression and polymorphism

Area of Science:

• Immunogenetics
• Aquaculture
• Comparative Immunology

Background:

• CD8 molecules are critical co-receptors for T cell activation in vertebrates.
• Understanding CD8 gene structure and expression in fish is essential for aquaculture health.
• Channel catfish (Ictalurus punctatus) are a vital food fish species with significant economic impact.

Purpose of the Study:

• To identify and characterize the CD8α and CD8β genes in channel catfish.
• To analyze the genomic organization and sequence features of catfish CD8 genes.
• To investigate the expression patterns of CD8α and CD8β in channel catfish lymphoid tissues.

Main Methods:

• Gene identification and sequencing of channel catfish CD8α and CD8β.
• Bioinformatic analysis of predicted protein structures and conserved motifs.
• Analysis of gene synteny and copy number.
• Quantitative PCR (q-PCR) to determine gene expression levels in various tissues.

Main Results:

• Identification and characterization of channel catfish CD8α and CD8β genes, encoding proteins with conserved structural features including a teleost-specific C-X-H motif in the cytoplasmic tail.
• Catfish CD8α and CD8β are single-copy genes with conserved head-to-tail synteny, with CD8β located upstream of CD8α.
• Low polymorphism in CD8α and CD8β transcripts was observed.
• Both CD8α and CD8β genes are expressed in various lymphoid tissues, with highest expression in the thymus of 2-month-old catfish fry.

Conclusions:

• The identified channel catfish CD8α and CD8β genes share conserved features with their counterparts in other vertebrates.
• The characterized gene structure and expression patterns provide a foundation for future studies on CD8-mediated immunity in catfish.
• These results will aid in evaluating the role of CD8(+) cytotoxic T lymphocytes (CTL) and other CD8-bearing cells in catfish immune responses to infection and vaccination.