GEPHE SUMMARY
Gephebase Gene
Entry Status
Published
GepheID
GP00000735
Main curator
Martin
PHENOTYPIC CHANGE
Trait Category
Trait State in Taxon A
Thamnophis sirtalis - sensitive
Trait State in Taxon B
Thamnophis sirtalis - resistant - Willow creek
Ancestral State
Taxon A
Taxonomic Status
Taxon A
Common Name
-
Synonyms
FMNH 73660; FMNH:73660
Rank
species
Lineage
Show more ... erygii; Dipnotetrapodomorpha; Tetrapoda; Amniota; Sauropsida; Sauria; Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera; Serpentes; Colubroidea; Colubridae; Natricinae; Thamnophis
NCBI Taxonomy ID
is Taxon A an Infraspecies?
No
Taxon B
Common Name
-
Synonyms
FMNH 73660; FMNH:73660
Rank
species
Lineage
Show more ... erygii; Dipnotetrapodomorpha; Tetrapoda; Amniota; Sauropsida; Sauria; Lepidosauria; Squamata; Bifurcata; Unidentata; Episquamata; Toxicofera; Serpentes; Colubroidea; Colubridae; Natricinae; Thamnophis
NCBI Taxonomy ID
is Taxon B an Infraspecies?
No
GENOTYPIC CHANGE
Presumptive Null
No
Molecular Type
Aberration Type
SNP
SNP Coding Change
Nonsynonymous
Molecular Details of the Mutation
Ile1709Val
Experimental Evidence
Taxon A Taxon B Position
Codon - - -
Amino-acid - - -
Authors
McGlothlin JW; Chuckalovcak JP; Janes DE; Edwards SV; Feldman CR; Brodie ED; Pfrender ME; Brodie ED
Abstract
Members of a gene family expressed in a single species often experience common selection pressures. Consequently, the molecular basis of complex adaptations may be expected to involve parallel evolutionary changes in multiple paralogs. Here, we use bacterial artificial chromosome library scans to investigate the evolution of the voltage-gated sodium channel (Nav) family in the garter snake Thamnophis sirtalis, a predator of highly toxic Taricha newts. Newts possess tetrodotoxin (TTX), which blocks Nav's, arresting action potentials in nerves and muscle. Some Thamnophis populations have evolved resistance to extremely high levels of TTX. Previous work has identified amino acid sites in the skeletal muscle sodium channel Nav1.4 that confer resistance to TTX and vary across populations. We identify parallel evolution of TTX resistance in two additional Nav paralogs, Nav1.6 and 1.7, which are known to be expressed in the peripheral nervous system and should thus be exposed to ingested TTX. Each paralog contains at least one TTX-resistant substitution identical to a substitution previously identified in Nav1.4. These sites are fixed across populations, suggesting that the resistant peripheral nerves antedate resistant muscle. In contrast, three sodium channels expressed solely in the central nervous system (Nav1.1-1.3) showed no evidence of TTX resistance, consistent with protection from toxins by the blood-brain barrier. We also report the exon-intron structure of six Nav paralogs, the first such analysis for snake genes. Our results demonstrate that the molecular basis of adaptation may be both repeatable across members of a gene family and predictable based on functional considerations.

© The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
Additional References
RELATED GEPHE
Related Haplotypes
No matches found.
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