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

ABSTRACT: 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.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.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.

SUBMITTER: Yaklichkin SY

PROVIDER: S-EPMC3207924 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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

Yaklichkin Sergey Yu SY Darnell Diana K DK Pier Maricela V MV Antin Parker B PB Hannenhalli Sridhar S

BMC evolutionary biology 20111015

<h4>Background</h4>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.<h4>Results</h4>In this study we identified the avian FOXE1 gene in chicken, turkey and zebra finch, all of which consist of a single exon. Chicke ...[more]

PMID: 21999483

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Project description:BACKGROUND:FOXE1, a thyroid-specific transcription factor also known as TTF-2, was recently identified as a major genetic risk factor for papillary thyroid carcinoma (PTC). Its role in thyroid carcinogenesis, however, remains unknown. The purpose of the present study was to assess the relationship between the FOXE1 immunohistochemical features and the clinical and genetic characteristics of PTC. METHODS:Immunohistochemical staining of FOXE1 was performed in 48 PTC cases. Two single nucleotide polymorphisms immediately inside (rs1867277) or in the vicinity (rs965513) of the FOXE1 gene were genotyped by direct sequencing. Histopathological, clinical, and genetic data were included in statistical analyses. RESULTS:FOXE1 exhibited cytoplasmic overexpression in tumor tissue compared to the normal counterpart (p<0.001). Both cancer and normal thyroid cells demonstrated the highest FOXE1 scores in the areas closest to the tumor border (<300 ?m) compared with more distant areas (p<0.001). No differences in FOXE1 staining distributions were found between microcarcinomas and PTC of larger size, between different histopathological variants of PTC, and encapsulated and nonencapsulated tumors. Multivariate regression analysis revealed that nuclear FOXE1 expression in neoplastic cells in the vicinity of the tumor border independently associated with the genotype at rs1867277 (the dominant model of inheritance, p=0.037) and tumor multifocality (p=0.032), and with marginal significance with capsular invasion (p=0.051). CONCLUSIONS:FOXE1 overexpression and translocation to the cytoplasm are phenotypic hallmarks of tumor cells suggesting that FOXE1 is involved in the pathogenesis of PTC. Nuclear FOXE1 expression in tumor cells in the vicinity of the PTC border is associated with the presence of a risk allele of rs1867277 (c.-238G>A) in the 5' untranslated region of the FOXE1 gene, as well as with pathological characteristics of PTC, suggesting possible FOXE1 involvement in the facilitation of tumor development beginning at an early stage.

Project description:BackgroundFoxE1 is a thyroid-specific forkhead transcription factor essential for thyroid gland development, as well as for the maintenance of the thyroid differentiated state in adults. FoxE1 recognizes and binds to a short DNA sequence present in thyroglobulin (Tg) and thyroperoxidase (Tpo) promoters, but FoxE1 binding to regulatory regions other than Tg and Tpo promoters remains almost unexplored. Improving knowledge of the regulatory functions of FoxE1 is necessary to clarify its role in endocrine syndromes and cancer susceptibility.Methodology/principal findingIn order to further investigate downstream FoxE1 targets, we performed a genome-wide expression screening after knocking-down FoxE1 and obtained new insights into FoxE1 transcriptional networks in thyroid follicular cells. After validation, we confirmed Adamts9, Cdh1, Duox2 and S100a4 as upregulated genes and Casp4, Creld2, Dusp5, Etv5, Hsp5a, Nr4a2 and Tm4sf1 as downregulated genes when FoxE1 was silenced. In promoter regions of putative FoxE1-regulated genes and also in the promoters of the classical thyroid genes Nis, Pax8 and Titf1, we performed an in silico search of the FoxE1 binding motif that was in close proximity to the NF1/CTF binding sequence, as previously described for other forkhead factors. Using chromatin immunoprecipitation we detected specific in vivo FoxE1 binding to novel regulatory regions in two relevant thyroid genes, Nis and Duox2. Moreover, we demonstrated simultaneous binding of FoxE1 and NF1/CTF to the Nis upstream enhancer region, as well as a clear functional activation of the Nis promoter by both transcription factors.Conclusions/significanceIn search for potential downstream mediators of FoxE1 function in thyroid cells, we identified two novel direct FoxE1 target genes. To our knowledge, this is the first evidence regarding the implication of Nis and Duox2 in executing the transcriptional program triggered by FoxE1. Furthermore, this study points out the important role of FoxE1 in the regulation of a large number of genes in thyroid cells.

Project description:BACKGROUND:Recent reports indicated that incidence of thyroid carcinoma is increasing throughout the worldwide. The aim of our study was to determine a possible relationship between Forkhead box E1 (FOXE1) gene variants and histopathological features of papillary thyroid carcinoma. METHODS:FOXE1 gene variations; rs894673, rs1867277 and rs3758249 were analyzed in 57 Papillary thyroid carcinoma patients and 51 age matched healthy control subjects. Restriction fragment length polymorphism (RFLP) technique was used to specifically detect the variations. RESULTS:There was a significant difference in the distribution of rs894673 genotypes in Papillary thyroid carcinoma cases (P=0.01). AA genotype presence of rs1867277 was more significantly associated with several histopathological parameters such as focal and diffuse capsular invasion, lymphatic invasion, P3 with P4 tumor grade and surgical margins. AA genotype presence in rs1867277 variation was significantly associated with the classical variant which is subtype of papillary thyroid carcinoma. Furthermore, the presence of the allel A was found to be related with lymph node invasion risk by 2.46 fold, capsular invasion risk by 2.97 fold, and pT3 with pT4 pathological stage risk by 4.13 fold and the presence of allele A in rs1867277 was significantly associated with classic variants. The presence of allele A in rs1867277 was more significantly associated with several histopathological parameters in classic variant in papillary thyroid carcinoma cases such as, the presence of the A allele was found relationship with lymph node invasion risk by 2.0 fold, capsular invasion risk by 2.39 fold , and pT3 with pT4 pathological stage risk by 3.57 fold. In addition, AATT, AAAA and GATT haplotypes (rs1867277 and rs894673) were evaluated for association with papillary thyroid carcinoma cases. Our results indicate that the significant difference according to two-allele haplotype distribution between papillary thyroid carcinoma cases and control groups. CONCLUSION:Our findings suggest that FOXE1 variations generate a higher risk for poor histopathological features of papillary thyroid carcinoma.

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

Publications

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

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