title: New insights into FoxE1 functions: identification of direct FoxE1 targets in thyroid cells.
abstract: BACKGROUND
  FoxE1 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.
  
  
  RESULTS
  In 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
  In 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.
authors.affiliation: Instituto de Investigaciones Biomédicas "Alberto Sols", Consejo Superior de Investigaciones Científicas, and Universidad Autónoma de Madrid-CSIC-UAM, Madrid, Spain.
authors.forename: Lara P
authors.initials: LP
authors.lastname: Fernández
authors.forename: Arístides
authors.initials: A
authors.lastname: López-Márquez
authors.forename: Angel M
authors.initials: AM
authors.lastname: Martínez
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Gómez-López
authors.forename: Pilar
authors.initials: P
authors.lastname: Santisteban
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D000074623:Dual Oxidases; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D027981:Symporters / Q000235:genetics / Q000378:metabolism*; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism*; D014158:Transcription, Genetic; D000099209:Sodium-Iodide Symporters
chemical_list: D000074623:Dual Oxidases; D005420:Flavoproteins; D051858:Forkhead Transcription Factors; D034741:RNA, Small Interfering; D027981:Symporters; D000099209:Sodium-Iodide Symporters; C526350:FoxE1 protein, rat; C486611:Duox2 protein, rat