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Dynamic evolution of toll-like receptor multigene families in echinoderms
Katherine M Buckley1, Jonathan P Rast
1Department of Immunology, Sunnybrook Research Institute, University of Toronto Toronto, ON, Canada.
Frontiers in Immunology
|June 9, 2012
Summary
The purple sea urchin genome reveals a complex immune system with numerous Toll-like receptor (TLR) sequences, significantly expanded compared to vertebrates. These TLRs show lineage-specific expansions, suggesting novel immune recognition functions in invertebrates.
Area of Science:
- Marine Biology
- Immunology
- Genomics
Background:
- The purple sea urchin (Strongylocentrotus purpuratus) is a large, long-lived invertebrate.
- Understanding animal immunity offers insights into evolutionary biology.
- Pattern recognition receptors (PRRs) are crucial for innate immunity in vertebrates.
Purpose of the Study:
- To analyze the genome sequence of Strongylocentrotus purpuratus.
- To investigate the complexity of its immune system, focusing on PRRs.
- To compare echinoderm Toll-like receptor (TLR) gene families with those in other taxa.
Main Methods:
- Genome sequencing and analysis of Strongylocentrotus purpuratus.
- Identification and characterization of gene families encoding PRRs, particularly TLRs.
- Phylogenetic analysis of TLR sequences within echinoderms and comparison with other metazoans.
Main Results:
- The sea urchin genome contains a highly expanded repertoire of immune genes, including 253 Toll-like receptor (TLR) sequences, over 200 Nod-like receptors, and 1095 scavenger receptor cysteine-rich domains.
- Sea urchin TLRs exhibit significant expansions largely independent of vertebrate and protostome lineages, with some ancient homologs.
- Phylogenetic analysis revealed lineage-specific TLR expansions in sea urchins, indicating rapid evolution and potential novel immune functions.
Conclusions:
- The purple sea urchin possesses a remarkably complex immune system with extensive TLR expansions.
- These expansions suggest unique immune recognition mechanisms in echinoderms.
- Comparative analysis highlights the evolutionary diversity of innate immunity across metazoans.
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