Origin and Evolution of the Sponge Aggregation Factor Gene Family

Area of Science:

• Evolutionary biology
• Genomics
• Immunology

Background:

• Self-nonself discrimination is crucial for animals, but homologous allorecognition genes are not apparent across metazoans.
• The Aggregation Factor (AF) gene family in sponges is investigated for its role in allorecognition.

Purpose of the Study:

• To characterize the Aggregation Factor (AF) gene family in the demosponge Amphimedon queenslandica.
• To trace the evolutionary history of the AF gene family across 24 sponge species.
• To propose the AF gene family as a model for understanding animal self-nonself recognition diversification.

Main Methods:

• Gene family characterization in Amphimedon queenslandica.
• Phylogenetic analysis of AF gene evolution across 24 sponge species.
• Analysis of AF gene domain organization and RNA editing patterns.

Main Results:

• The AF locus in Amphimedon contains five polymorphic genes encoding Calx-beta, Von Willebrand, and Wreath domains.
• AF gene family presence is restricted to demosponges, with significant variation in repertoire and domain organization among species.
• RNA editing contributes to AF variance, and diversification involves high allelism and rapid domain shuffling.

Conclusions:

• The sponge AF gene family exhibits rapid evolution through high allelism and domain dynamics.
• The diversification of AFs in sponges offers a model for the evolution of self-nonself recognition systems in the broader animal kingdom.