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Rates of molecular evolution vary in vertebrates for insulin-like growth factor-1 (IGF-1), a pleiotropic locus that regulates life history traits.

Abstract：

:Insulin-like growth factor-1 (IGF-1) is a member of the vertebrate insulin/insulin-like growth factor/relaxin gene family necessary for growth, reproduction, and survival at both the cellular and organismal level. Its sequence, protein structure, and function have been characterized in mammals, birds, and fish; however, a notable gap in our current knowledge of the function of IGF-1 and its molecular evolution is information in ectothermic reptiles. To address this disparity, we sequenced the coding region of IGF-1 in 11 reptile species-one crocodilian, three turtles, three lizards, and four snakes. Complete sequencing of the full mRNA transcript of a snake revealed the Ea-isoform, the predominant isoform of IGF-1 also reported in other vertebrate groups. A gene tree of the IGF-1 protein-coding region that incorporated sequences from diverse vertebrate groups showed similarity to the species phylogeny, with the exception of the placement of Testudines as sister group to Aves, due to their high nucleotide sequence similarity. In contrast, long-branch lengths indicate more rapid divergence in IGF-1 among lizards and snakes. Additionally, lepidosaurs (i.e., lizards and snakes) had higher rates of non-synonymous:synonymous substitutions (dN/dS) relative to archosaurs (i.e., birds and crocodilians) and turtles. Tests for positive selection on specific codons within branches and evaluation of the changes in the amino acid properties, suggested positive selection in lepidosaurs on the C domain of IGF-1, which is involved in binding affinity to the IGF-1 receptor. Predicted structural changes suggest that major alterations in protein structure and function may have occurred in reptiles. These data propose new insights into the molecular co-evolution of IGF-1 and its receptors, and ultimately the evolution of IGF-1's role in regulating life-history traits across vertebrates.

journal_name

Gen Comp Endocrinol

journal_title

General and comparative endocrinology

authors

Sparkman AM,Schwartz TS,Madden JA,Boyken SE,Ford NB,Serb JM,Bronikowski AM

doi

10.1016/j.ygcen.2012.04.022

subject

Has Abstract

pub_date

2012-08-01 00:00:00

pages

164-73

issue

eissn

0016-6480

issn

1095-6840

pii

S0016-6480(12)00182-7

journal_volume

178

pub_type

杂志文章

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Rates of molecular evolution vary in vertebrates for insulin-like growth factor-1 (IGF-1), a pleiotropic locus that regulates life history traits.