Publications (2)6.92 Total impact
-
Article: Thyroid hormone-regulated gene expression in juvenile mouse liver: identification of thyroid response elements using microarray profiling and in silico analyses.
[show abstract] [hide abstract]
ABSTRACT: 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. 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. 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.BMC Genomics 12/2011; 12:634. · 4.07 Impact Factor -
Article: Lack of change in microRNA expression in adult mouse liver following treatment with benzo(a)pyrene despite robust mRNA transcriptional response.
[show abstract] [hide abstract]
ABSTRACT: Benzo(a)pyrene (BaP) is a mutagenic and carcinogenic environmental contaminant. Metabolic activation of BaP is required for it to exert its mutagenic effects. Metabolism occurs via BaP interaction with the aryl hydrocarbon receptor (AHR) resulting in induction of phase 1 enzymes. Exposure to BaP is expected to cause differential regulation of AHR-responsive genes as well as pathways responding to DNA damage induced by its metabolites. MicroRNAs (miRNAs) are short non-coding molecules that control mRNA levels and protein translation. MiRNA regulation may also be affected by chemical insult. Here we investigate the correlation between hepatic mRNA and miRNA response to BaP in vivo. Mature male mice were orally exposed to 3 daily doses of 150mg/kg BaP. DNA microarrays were used to profile gene and miRNA expression in the liver 4 and 24h following the final dose. Despite widespread changes in gene expression (>400 genes) in pathways consistent with the known effects of BaP, we found no changes in miRNA. This was confirmed on two microarray platforms and by qRT-PCR. Analysis of positive controls (2 distinct reference pools) indicated that the Agilent technology could identify differences in miRNA. The effects of sample storage at -80°C were also compared. We found little effect of prolonged freezing on the technical correlation between samples or on differential expression. Our results are consistent with the lack of response of miRNA in rodent liver to dioxin, another potent AHR-agonist. We conclude that hepatic miRNA in vivo is not directly responsive to BaP exposure.Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 02/2010; 722(2):131-9. · 2.85 Impact Factor
