Accelerated evolution of 3'avian FOXE1 genes, and thyroid and feather specific expression of chicken FoxE1

Sergey Yu Yaklichkin, Diana K. Darnell, Maricela V. Pier, Parker B Antin, Sridhar Hannenhalli

Research output: Contribution to journalArticle

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Abstract

Background: The forkhead transcription factor gene E1 (FOXE1) plays an important role in regulation of thyroid development, palate formation and hair morphogenesis in mammals. However, avian FOXE1 genes have not been characterized and as such, codon evolution of FOXE1 orthologs in a broader evolutionary context of mammals and birds is not known. Results: In this study we identified the avian FOXE1 gene in chicken, turkey and zebra finch, all of which consist of a single exon. Chicken and zebra finch FOXE1 are uniquely located on the sex-determining Z chromosome. In situ hybridization shows that chicken FOXE1 is specifically expressed in the developing thyroid. Its expression is initiated at the placode stage and is maintained during the stages of vesicle formation and follicle primordia. Based on this expression pattern, we propose that avian FOXE1 may be involved in regulating the evagination and morphogenesis of thyroid. Chicken FOXE1 is also expressed in growing feathers. Sequence analysis identified two microdeletions in the avian FOXE1 genes, corresponding to the loss of a transferable repression domain and an engrailed homology motif 1 (Eh1) C-terminal to the forkhead domain. The avian FOXE1 proteins exhibit a significant sequence divergence of the C-terminus compared to those of amphibian and mammalian FOXE1. The codon evolution analysis (dN/dS) of FOXE1 shows a significantly increased dN/dS ratio in the avian lineages, consistent with either a relaxed purifying selection or positive selection on a few residues in avian FOXE1 evolution. Further site specific analysis indicates that while relaxed purifying selection is likely to be a predominant cause of accelerated evolution at the 3'-region of avian FOXE1, a few residues might have evolved under positive selection. Conclusions: We have identified three avian FOXE1 genes based on synteny and sequence similarity as well as characterized the expression pattern of the chicken FOXE1 gene during development. Our evolutionary analyses suggest that while a relaxed purifying selection is likely to be the dominant force driving accelerated evolution of avian FOXE1 genes, a few residues may have evolved adaptively. This study provides a basis for future genetic and comparative biochemical studies of FOXE1.

Original languageEnglish (US)
Article number302
JournalBMC Evolutionary Biology
Volume11
Issue number1
DOIs
StatePublished - 2011

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feather
feathers
chickens
gene
genes
Taeniopygia guttata
morphogenesis
codons
mammal
mammals
Z chromosome
palate
sex chromosomes
vesicle
homology
hair
amphibian
in situ hybridization
exons
hairs

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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Accelerated evolution of 3'avian FOXE1 genes, and thyroid and feather specific expression of chicken FoxE1. / Yaklichkin, Sergey Yu; Darnell, Diana K.; Pier, Maricela V.; Antin, Parker B; Hannenhalli, Sridhar.

In: BMC Evolutionary Biology, Vol. 11, No. 1, 302, 2011.

Research output: Contribution to journalArticle

Yaklichkin, Sergey Yu ; Darnell, Diana K. ; Pier, Maricela V. ; Antin, Parker B ; Hannenhalli, Sridhar. / Accelerated evolution of 3'avian FOXE1 genes, and thyroid and feather specific expression of chicken FoxE1. In: BMC Evolutionary Biology. 2011 ; Vol. 11, No. 1.
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