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Origin and convergent evolution of exendin genes
1Department of Laboratory Medicine and Pathobiology, 1 King's College Circle, University of Toronto, Toronto, Ont, Canada M5S 1A8. david.irwin@utoronto.ca
General and Comparative Endocrinology
|December 6, 2011
Summary
Exendins, peptides from Gila monster venom, evolved rapidly in the Heloderma lineage. Exendins-1 and -2 convergently evolved to mimic vasoactive intestinal peptide (VIP), while exendins-3 and -4 retained glucagon-like peptide-1 (GLP-1) similarity.
Area of Science:
- Evolutionary biology
- Molecular evolution
- Biochemistry
Background:
- Exendins are venom peptides from Heloderma lizards, with subtypes showing similarity to VIP and GLP-1.
- The evolutionary history and gene origins of exendins remained largely unknown.
- Recent discoveries of exendin orthologs in various vertebrates provided new insights.
Purpose of the Study:
- To elucidate the evolutionary origin and diversification of exendin peptides and their encoding genes.
- To investigate the evolutionary rates and functional convergence of exendin sequences.
- To understand the ancestral function of exendins based on their evolutionary relationships.
Main Methods:
- Comparative sequence analysis of exendin genes and peptides across different vertebrate species.
- Phylogenetic analysis to reconstruct the evolutionary history of exendins.
- Identification and analysis of gene duplication events in the Heloderma lineage.
Main Results:
- Heloderma exendins originated from a common ancestor via gene duplication after divergence from other reptiles.
- Exendin toxin peptide sequences evolved rapidly on the Heloderma lineage, adapting to their toxic function.
- Exendins-1 and -2 convergently evolved to resemble VIP, while exendins-3 and -4 retained GLP-1-like characteristics.
Conclusions:
- The rapid evolution of exendin toxins is linked to adaptation in the Heloderma lineage.
- Convergent evolution shaped exendin-1 and -2 towards VIP-like functions.
- The ancestral exendin peptide likely shared similarities with proglucagon-derived peptides or GIP, suggesting a conserved ancestral role.
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