Thyroid hormone-regulated gene expression in juvenile mouse liver: identification of thyroid response elements using microarray profiling and in silico analyses.
BACKGROUND
Disruption of thyroid hormone signalling can alter growth, development and energy metabolism. Thyroid hormones exert their effects through interactions with thyroid receptors that directly bind thyroid response elements and can alter transcriptional activity of target genes. The effects of short-term thyroid hormone perturbation on hepatic mRNA transcription in juvenile mice were evaluated, with the goal of identifying genes containing active thyroid response elements. Thyroid hormone disruption was induced from postnatal day 12 to 15 by adding goitrogens to dams' drinking water (hypothyroid). A subgroup of thyroid hormone-disrupted pups received intraperitoneal injections of replacement thyroid hormones four hours prior to sacrifice (replacement). An additional group received only thyroid hormones four hours prior to sacrifice (hyperthyroid). Hepatic mRNA was extracted and hybridized to Agilent mouse microarrays.


RESULTS
Transcriptional profiling enabled the identification of 28 genes that appeared to be under direct thyroid hormone-regulation. The regulatory regions of the genome adjacent to these genes were examined for half-site sequences that resemble known thyroid response elements. A bioinformatics search identified 33 thyroid response elements in the promoter regions of 13 different genes thought to be directly regulated by thyroid hormones. Thyroid response elements found in the promoter regions of Tor1a, 2310003H01Rik, Hect3d and Slc25a45 were further validated by confirming that the thyroid receptor is associated with these sequences in vivo and that it can bind directly to these sequences in vitro. Three different arrangements of thyroid response elements were identified. Some of these thyroid response elements were located far up-stream (> 7 kb) of the transcription start site of the regulated gene.


CONCLUSIONS
Transcriptional profiling of thyroid hormone disrupted animals coupled with a novel bioinformatics search revealed new thyroid response elements associated with genes previously unknown to be responsive to thyroid hormone. The work provides insight into thyroid response element sequence motif characteristics.
Environmental Health Sciences and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, 50 Colombine Driveway, Ottawa, Ontario K1A 0K9, Canada.
Martin A
MA
Paquette
Hongyan
H
Dong
Rémi
R
Gagné
Andrew
A
Williams
Morie
M
Malowany
Mike G
MG
Wade
Carole L
CL
Yauk
D000818:Animals; D001483:Base Sequence; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018832:Molecular Chaperones / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011988:Receptors, Thyroid Hormone / Q000378:metabolism; D020218:Response Elements / Q000235:genetics*; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000235:genetics; D013961:Thyroid Gland / Q000378:metabolism; D013963:Thyroid Hormones / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D044767:Ubiquitin-Protein Ligases / Q000235:genetics
C491548:Dyt1 protein, mouse; D018832:Molecular Chaperones; D012333:RNA, Messenger; D011988:Receptors, Thyroid Hormone; D013963:Thyroid Hormones; C539188:HECTd3 protein, mouse; D044767:Ubiquitin-Protein Ligases