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B cell receptor accessory molecule CD79α: characterisation and expression analysis in a cartilaginous fish, the spiny
Ronggai Li1, Tiehui Wang, Steve Bird
1Scottish Fish Immunology Research Centre, University of Aberdeen, Aberdeen, UK.
Insights
Researchers identified and studied the spiny dogfish CD79α (SaCD79α), a key protein in B cell signaling. This finding suggests SaCD79α may serve as a reliable pan-B cell marker in sharks, similar to its role in mammals.
Area of Science:
- Immunology
- Molecular Biology
- Comparative Genomics
Background:
- CD79α (Igα) is crucial for B cell receptor signaling and is a specific marker for B cells in mammals.
- Understanding CD79α function in non-mammalian vertebrates like sharks can provide insights into immune system evolution.
Purpose of the Study:
- To describe the spiny dogfish CD79α (SaCD79α) gene and protein.
- To investigate the expression patterns of SaCD79α in spiny dogfish under different conditions.
- To evaluate SaCD79α as a potential pan-B cell marker in sharks.
Main Methods:
- Cloning and sequencing of the spiny dogfish CD79α cDNA.
- Bioinformatic analysis of gene structure and regulatory regions.
- Quantitative expression analysis in various immune tissues and peripheral blood cells.
- Stimulation assays using pokeweed mitogen.
Main Results:
- The spiny dogfish CD79α cDNA encodes a 205-amino acid protein, with conserved gene structure across species.
- SaCD79α is highly expressed in immune organs (spleen, epigonal, Leydig) and correlates with immunoglobulin heavy chains.
- CD79α transcription is significantly upregulated in peripheral blood cells after pokeweed mitogen stimulation.
- The 5' flanking region lacks a TATA box but contains transcription factor binding sites crucial for B cell-specific expression.
Conclusions:
- Spiny dogfish CD79α is expressed by B cells and likely forms a functional B cell receptor complex, analogous to mammals.
- SaCD79α represents a conserved pan-B cell marker for immunological studies in sharks.
- This study enhances our understanding of B cell receptor complex evolution in vertebrates.
Abstract:
CD79α (also known as Igα) is a component of the B cell antigen receptor complex and plays an important role in B cell signalling. The CD79α protein is present on the surface of B cells throughout their life cycle, and is absent on all other healthy cells, making it a highly reliable marker for B cells in mammals. In this study the spiny dogfish (Squalus acanthias) CD79α (SaCD79α) is described and its expression studied under constitutive and stimulated conditions. The spiny dogfish CD79α cDNA contains an open reading frame of 618 bp, encoding a protein of 205 amino acids. Comparison of the SaCD79α gene with that of other species shows that the gross structure (number of exons, exon/intron boundaries, etc.) is highly conserved across phylogeny. Additionally, analysis of the 5' flanking region shows SaCD79α lacks a TATA box and possesses binding sites for multiple transcription factors implicated in its B cell-specific gene transcription in other species. Spiny dogfish CD79α is most highly expressed in immune tissues, such as spleen, epigonal and Leydig organ, and its transcript level significantly correlates with those of spiny dogfish immunoglobulin heavy chains. Additionally, CD79α transcription is up-regulated, to a small but significant degree, in peripheral blood cells following stimulation with pokeweed mitogen. These results strongly indicate that, as in mammals, spiny dogfish CD79α is expressed by shark B cells where it associates with surface-bound immunoglobulin to form a fully functional BCR, and thus may serve as a pan-B cell marker in future shark immunological studies.
