title: The zebrafish thyroid hormone receptor alpha 1 is expressed during early embryogenesis and can function in transcriptional repression.
abstract: Nuclear receptors are a large family of ligand dependent transcription factors which participate in many diverse processes during development. In this report, we describe the cloning of the zebrafish thyroid hormone receptor alpha 1 (TR alpha 1) gene, the cellular counterpart of the viral oncogene v-erbA. TR alpha 1 is expressed during oogenesis and maternally supplied to the embryo. TR alpha 1 is expressed again after the mid blastula transition. By examining the effects of increased expression of TR alpha 1 on expression of a reporter gene which responds to both TR alpha 1 and retinoic acid receptors (RARs), we show that the zebrafish TR alpha 1 can act as a repressor during early zebrafish development before thyroid hormone is present in the embryo. In addition, our data suggest that TR alpha 1 can repress retinoic acid (RA)-signaling during early development. We propose that TR alpha 1 functions during early development as a transcriptional repressor, similar to the constitutive repressor activity of its viral counterpart v-erbA, which regulates anterior-posterior (A/P) patterning by repressing RA-signaling.
authors.affiliation: Department of Genetics and Cell Biology, University of Minnesota, St. Paul 55108-1095, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Essner
authors.forename: J J
authors.initials: JJ
authors.lastname: Breuer
authors.forename: R D
authors.initials: RD
authors.lastname: Essner
authors.forename: S C
authors.initials: SC
authors.lastname: Fahrenkrug
authors.forename: P B
authors.initials: PB
authors.lastname: Hackett
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001755:Blastocyst / Q000378:metabolism; D015152:Blotting, Northern; D003001:Cloning, Molecular; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D005775:Gastrula / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D009866:Oogenesis / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000235:genetics* / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology; D012260:Ribonucleases / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014212:Tretinoin / Q000378:metabolism; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D012097:Repressor Proteins; D014212:Tretinoin; D012260:Ribonucleases