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Constraint shapes convergence in tetrodotoxin-resistant sodium channels of snakes.
Proc Natl Acad Sci U S A. 2012 Mar 20; 109(12):4556-61
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02 Apr 2012
New Finding
DOI: 10.3410/f.14262963.15775067
Utilizing a truly integrative approach that combines genetics, cell biology, and natural history, Feldman et al. examine the molecular basis of convergent evolution in several snakes with adaptations allowing them to consume prey expressing deadly tetrodotoxin. Whether convergent phenotypes arise through...Continue reading
Utilizing a truly integrative approach that combines genetics, cell biology, and natural history, Feldman et al. examine the molecular basis of convergent evolution in several snakes with adaptations allowing them to consume prey expressing deadly tetrodotoxin. Whether convergent phenotypes arise through the same genetic changes or from unique mutations is a major question in evolution, and the authors show that resistance to tetrodotoxin has evolved repeatedly across diverse lineages through changes in a small number of amino acids, suggesting that evolutionary convergence may be shaped by functional constraints which limit the spectrum of genetic variation on which natural selection can act.
Disclosures
None declared
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Losos J and Wang I: F1000Prime Recommendation of [Feldman CR et al., Proc Natl Acad Sci U S A 2012, 109(12):4556-61]. In F1000Prime, 02 Apr 2012; DOI: 10.3410/f.14262963.15775067. F1000Prime.com/14262963#eval15775067
F1000Prime Recommendations, Dissents and Comments for [Feldman CR et al., Proc Natl Acad Sci U S A 2012, 109(12):4556-61]. In F1000Prime, 25 May 2013; F1000Prime.com/14262963
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Natural selection often produces convergent changes in unrelated lineages, but the degree to which such adaptations occur via predictable genetic paths is unknown. If only a limited subset of possible mutations is fixed in independent lineages, then it is clear that constraint in the production or function of molecular variants is an important determinant of adaptation. We demonstrate remarkably constrained convergence during the evolution of resistance to the lethal poison, tetrodotoxin, in six snake species representing three distinct lineages from around the globe. Resistance-conferring amino acid substitutions in a voltage-gated sodium channel, Na(v)1.4, are clustered in only two regions of the protein, and a majority of the replacements are confined to the same three positions. The observed changes represent only a small fraction of the experimentally validated mutations known to increase Na(v)1.4 resistance to tetrodotoxin. These results suggest that constraints resulting from functional tradeoffs between ion channel function and toxin resistance led to predictable patterns of evolutionary convergence at the molecular level. Our data are consistent with theoretical predictions and recent microcosm work that suggest a predictable path is followed during an adaptive walk along a mutational landscape, and that natural selection may be frequently constrained to produce similar genetic outcomes even when operating on independent lineages.
PMID: 22392995
