Project description:In this study we used the d337T TRb transgenic mouse that has been created to reproduce the human genetic disease known as resistance to thyroid hormone (RTH) as a model to determine if the d337T TRb mutation would have an effect on PPARa activation. A single amino acid deletion (d337T) abrogates thyroid hormone (T3) binding and transforms the thyroid hormone receptor (TRb) into a constitutive repressor. The principle goal was to determine if T3 regulates myocardial energy metabolism through its nuclear receptors. We introduced a known PPARa activator (WY14, 643) into control and d337T TRb transgenic mice then examined cardiac gene expression using Affymetrix 430_2 expression arrays and RT-PCR. We compared the gene expression of PPARa, RXRb and TRa,b and three PPARa target genes among four studies groups [control, control with WY14, 643, d337T TRb, and d337T TRb with WY14, 643] consisting of seven mice per group. Microarray analysis revealed that these genes responded to the WY14, 643 treatments of control and d337T TRb mice. Analysis of the array and RT-PCR data indicates that mRNA expression levels of PPARa and mRXRb decrease after a six hour drug treatment in both control and d337T TRb mice (P<0.01) as did the array mRNA expression levels for TRa & b (P<0.025). Three target genes (AMPD3, PDK4 and UCP3) of PPARa were up regulated in control and down regulated in the d337T TRb transgenic mouse, indicating a direct action on these metabolic genes when the TRb becomes a repressor. In conclusion, PPARa activation by WY14, 643 has a positive effect on control mice and a negative effect on the TRb transgenic mice which supports our hypothesis that T3 regulates myocardial energy metabolism through its nuclear receptors. Experiment Overall Design: 7 control, 7 deletion strain individuals, 7 controls with a PPARalpha activator, 7 deletion strain individuals with a PPARalpha activator
Project description:In this study we used the d337T TRb transgenic mouse that has been created to reproduce the human genetic disease known as resistance to thyroid hormone (RTH) as a model to determine if the d337T TRb mutation would have an effect on PPARa activation. A single amino acid deletion (d337T) abrogates thyroid hormone (T3) binding and transforms the thyroid hormone receptor (TRb) into a constitutive repressor. The principle goal was to determine if T3 regulates myocardial energy metabolism through its nuclear receptors. We introduced a known PPARa activator (WY14, 643) into control and d337T TRb transgenic mice then examined cardiac gene expression using Affymetrix 430_2 expression arrays and RT-PCR. We compared the gene expression of PPARa, RXRb and TRa,b and three PPARa target genes among four studies groups [control, control with WY14, 643, d337T TRb, and d337T TRb with WY14, 643] consisting of seven mice per group. Microarray analysis revealed that these genes responded to the WY14, 643 treatments of control and d337T TRb mice. Analysis of the array and RT-PCR data indicates that mRNA expression levels of PPARa and mRXRb decrease after a six hour drug treatment in both control and d337T TRb mice (P<0.01) as did the array mRNA expression levels for TRa & b (P<0.025). Three target genes (AMPD3, PDK4 and UCP3) of PPARa were up regulated in control and down regulated in the d337T TRb transgenic mouse, indicating a direct action on these metabolic genes when the TRb becomes a repressor. In conclusion, PPARa activation by WY14, 643 has a positive effect on control mice and a negative effect on the TRb transgenic mice which supports our hypothesis that T3 regulates myocardial energy metabolism through its nuclear receptors. Keywords: treatment and deletion effects
Project description:Characterization of Directly Regulated Thyroid Hormone Mediated Gene Expression Following Short-Term Perturbations in Thyroid Hormone Levels in Juvenile Mice
Project description:Sex differences in liver gene expression are dictated by sex-differences in circulating growth hormone (GH) profiles. Presently, the pituitary hormone dependence of mouse liver gene expression was investigated on a global scale to discover sex-specific early GH response genes that might contribute to sex-specific regulation of downstream GH targets and to ascertain whether intrinsic sex-differences characterize hepatic responses to plasma GH stimulation. RNA expression analysis using 41,000-feature microarrays revealed two distinct classes of sex-specific mouse liver genes: genes subject to positive regulation (class-I) and genes subject to negative regulation by pituitary hormones (class-II). Genes activated or repressed in hypophysectomized (Hypox) mouse liver within 30-90min of GH pulse treatment at a physiological dose were identified as direct targets of GH action (early response genes). Intrinsic sex-differences in the GH responsiveness of a subset of these early response genes were observed. Notably, 45 male-specific genes, including five encoding transcriptional regulators that may mediate downstream sex-specific transcriptional responses, were rapidly induced by GH (within 30min) in Hypox male but not Hypox female mouse liver. The early GH response genes were enriched in 29 male-specific targets of the transcription factor Mef2, whose activation in hepatic stellate cells is associated with liver fibrosis leading to hepatocellular carcinoma, a male-predominant disease. Thus, the rapid activation by GH pulses of certain sex-specific genes is modulated by intrinsic sex-specific factors, which may be associated with prior hormone exposure (epigenetic mechanisms) or genetic factors that are pituitary-independent, and could contribute to sex-differences in predisposition to liver cancer or other hepatic pathophysiologies.