Regulator of complement activation (RCA) group 2 gene cluster in zebrafish: identification, expression, and evolution

Area of Science:

• Immunology
• Genomics
• Evolutionary Biology

Background:

• The complement system is crucial for host defense and requires tight regulation by specific proteins.
• These regulatory proteins are encoded by genes clustered in the regulator of complement activation (RCA) locus.
• While RCA group 1 genes are known in zebrafish, RCA group 2 information in fish is limited.

Purpose of the Study:

• To identify and characterize RCA group 2 genes in zebrafish.
• To investigate the genomic organization and evolutionary relationships of these genes.
• To explore the potential functional divergence of identified RCA genes.

Main Methods:

• Bioinformatic analysis to identify ZRC1 and ZRC2 genes in zebrafish.
• Comparative genomics to analyze gene linkage and arrangement relative to PFKFB genes.
• Sequence identity analysis to infer gene duplication events.
• Expression pattern analysis to assess functional divergence.

Main Results:

• Two novel, closely linked RCA group 2 genes, ZRC1 and ZRC2, were identified in zebrafish.
• These genes exhibit characteristics of known RCA group 2 genes and are linked to PFKFB1, differing from the PFKFB2 linkage in other vertebrates.
• Zebrafish ZRC1 and ZRC2 show high sequence identity, suggesting a gene duplication origin.
• ZRC1 and ZRC2 encode distinct protein types (membrane-associated and soluble) with differing expression patterns, indicating functional divergence.

Conclusions:

• This study reports the first identification of the RCA group 2 gene cluster in zebrafish.
• The findings provide insights into the origin and evolution of RCA proteins, particularly the presence of membrane-associated complement regulatory proteins in fish.
• The identified genes and their characteristics contribute to a better understanding of complement system regulation in vertebrates.