Stéphanie Decherf | Muséum National d'Histoire Naturelle (original) (raw)
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Papers by Stéphanie Decherf
Methods in molecular biology (Clifton, N.J.), 2008
RNA interference mediated by small interfering RNAs (siRNAs) is a powerful tool for evaluating ge... more RNA interference mediated by small interfering RNAs (siRNAs) is a powerful tool for evaluating gene function in vivo. In particular it should be able to provide tissue-specific and developmental stage-specific knockdown of target genes in physiological contexts. However, there are few demonstrations of its use on neuronal specific genes in vivo. We recently developed a cationic lipid-based approach to study gene function in a neuronal context. In particular, we applied it to study how the novel partner for TRbeta1, hepatitis virus B X-associated protein 2 (XAP2), a protein first identified as a co-chaperone protein, affects T3-transcriptional repression of the hypothalamic gene, TRH. The cationic lipid-based technique used, JetSI/DOPE, was previously shown to efficiently knockdown reporter gene mRNA in vivo. Using JetSI/DOPE to vectorize siRNA against XAP2 mRNA, we show that XAP2 is needed specifically for TRbeta1-mediated (but not TRbeta2) activation of hypothalamic TRH transcripti...
Molecular and Cellular Endocrinology, 2010
Thyroid hormone receptor (TR) and peroxisome proliferator-activated receptor γ (PPARγ) co-regulat... more Thyroid hormone receptor (TR) and peroxisome proliferator-activated receptor γ (PPARγ) co-regulate numerous peripheral metabolic responses. To examine potential crosstalk between PPARγ and TRβ in the hypothalamus, thyrotropin-releasing hormone (Trh) regulation in the newborn mouse hypothalamus was followed. QPCR showed PPARγ to be expressed in the hypothalamus at this developmental stage. Intracerebral injection of PPARγ agonists modified transcription from a TRH-luc
Proceedings of the National Academy of Sciences, 2010
The melanocortin receptor Mc4r, a key relay in leptin signaling, links central energy control to ... more The melanocortin receptor Mc4r, a key relay in leptin signaling, links central energy control to peripheral reserve status. Mc4r activation in different brain areas reduces food intake and increases energy expenditure. Mice lacking Mc4r are obese. Mc4r is expressed by hypothalamic paraventricular thyrotropin-releasing hormone (TRH) neurons and increases energy usage through Trh activation and thyroid hormone (trio-iodothyronine, T 3 ) production. These facts led us to test the hypothesis that energy homoeostasis should require negative feedback by T 3 on Mc4r expression. QPCR and in situ hybridization showed hyperthyroidism to reduce Mc4r mRNA levels in the paraventricular nucleus. Comparative in silico analysis of Mc4r regulatory regions revealed two evolutionarily conserved potential negative thyroid hormone response elements (nTREs). In vivo chromatin immunoprecipitation (ChIP) on mouse hypothalamus demonstrated association of thyroid hormone receptors (TR) with a region spanning one nTRE. Further, in vivo gene reporter assays revealed dose-dependent T 3 repression of transcription from the Mc4r promoter in mouse hypothalamus, in parallel with T 3dependent Trh repression. Mutagenesis of the nTREs in the Mc4r promoter demonstrated direct regulation by T 3 , consolidating the ChIP results. In vivo shRNA knockdown, TR over-expression approaches and use of mutant mice lacking specific TRs, showed that both TRα and TRβ contribute to Mc4r regulation. T 3 repression of Mc4r transcription ensures that the energy-saving effects of T 3 feedback on Trh are not over-ridden by Mc4r activation of Trh. Thus, parallel repression by T 3 on hypothalamic Mc4r and Trh contributes to energy homeostasis.
PLoS ONE, 2014
Mammalian thyroid hormone receptors (TRs) have multiple isoforms, including the bona fide recepto... more Mammalian thyroid hormone receptors (TRs) have multiple isoforms, including the bona fide receptors that bind T 3 (TRa1, TRb1 and TRb2) and a non-hormone-binding variant, TRa2. Intriguingly, TRa2 is strongly expressed in the brain, where its mRNA levels exceed those of functional TRs. Ablation of TRa2 in mice results in over-expression of TRa1, and a complex phenotype with low levels of free T 3 and T 4 , without elevated TSH levels, suggesting an alteration in the negative feedback at the hypothalamic-pituitary level. As the hypothesis of a potential TRH response defect has never been tested, we explored the functional role of TRa2 in negative feedback on transcription of hypothalamic thyrotropin, Trh. The in vivo transcriptional effects of TRa2 on hypothalamic Trh were analysed using an in vivo reporter gene approach. Effects on Trhluc expression were examined to that of two, T 3 positively regulated genes used as controls. Applying in vivo gene transfer showed that TRa2 over-expression in the mouse hypothalamus abrogates T 3 -dependent repression of Trh and T 3 activation of positively regulated promoters, blocking their physiological regulation. Surprisingly, loss of function studies carried out by introducing a shTRa2 construct in the hypothalamus also blocked physiological T 3 dependent regulation. Thus, modulating hypothalamic TRa2 expression by either gain or loss of function abrogated T 3 dependent regulation of Trh transcription, producing constant transcriptional levels insensitive to feedback. This loss of physiological regulation was reflected at the level of the endogenous Trh gene, were gain or loss of function held mRNA levels constant. These results reveal the as yet undescribed dominant negative role of TRa2 over TRa1 effect on hypothalamic Trh transcription.
Molecular and Cellular Endocrinology, 2013
How Retinoid X receptors (RXR) and thyroid hormone receptors (TR) interact on negative TREs and w... more How Retinoid X receptors (RXR) and thyroid hormone receptors (TR) interact on negative TREs and whether RXR subtype specificity is determinant in such regulations is unknown. In a set of functional studies, we analyzed RXR subtype effects in T 3 -dependent repression of hypothalamic thyrotropinreleasing hormone (Trh). Two-hybrid screening of a hypothalamic paraventricular nucleus cDNA bank revealed specific, T 3 -dependent interaction of TRs with RXRb. In vivo chromatin immuno-precipitation showed recruitment of RXRs to the TRE-site 4 region of the Trh promoter in the absence of T 3 . In vivo overexpression of RXRa in the mouse hypothalamus heightened T 3 -independent Trh transcription, whereas RXRb overexpression abrogated this activity. Loss of function of RXRa and b by shRNAs induced inverse regulations. Thus, RXRa and RXRb display specific roles in modulating T 3 -dependent regulation of Trh. These results provide insight into the actions of these different TR heterodimerization partners within the context of a negatively regulated gene.
Molecular and Cellular Endocrinology, 2010
The hypothalamus integrates metabolic and endocrine signals. As such it represents a potential ta... more The hypothalamus integrates metabolic and endocrine signals. As such it represents a potential target for a wide spectrum of endocrine disrupting chemicals (EDCs). We investigated hypothalamic effects of two environmentally abundant xenobiotics, the flame-retardant tetrabromo bisphenol A (TBBPA) and the anti-fouling agent tributyltin (TBT). These EDCs affect endocrine signalling through different nuclear receptors including the thyroid hormone receptor (TR) or its partner, the retinoid X receptor (RXR). Promoter sequences of two hypothalamic genes implicated in metabolic control and regulated by thyroid hormone, thyrotropin-releasing hormone (Trh) and type 4 melanocortin receptor (Mc4r), were studied in vivo using reporter assays. Chronic exposure of gestating dams or acute exposure of their newborns to TBBPA abrogated activation of both Trh and Mc4r transcription. Exposure of lactating dams to TBT amplified activation of Trh without affecting Mc4r transcription. Thus, perinatal exposure to EDCs affecting nuclear receptor signalling modulates hypothalamic set-points controlling metabolic responses.
Journal of Toxicology and Environmental Health, Part B, 2011
Embo Reports, 2006
Transcriptional control of hypothalamic thyrotropin-releasing hormone (TRH) integrates central re... more Transcriptional control of hypothalamic thyrotropin-releasing hormone (TRH) integrates central regulation of the hypothalamohypophyseal-thyroid axis and hence thyroid hormone (triiodothyronine (T 3 )) homeostasis. The two b thyroid hormone receptors, TRb1 and TRb2, contribute to T 3 feedback on TRH, with TRb1 having a more important role in the activation of TRH transcription. How TRb1 fulfils its role in activating TRH gene transcription is unknown. By using a yeast two-hybrid screening of a mouse hypothalamic complementary DNA library, we identified a novel partner for TRb1, hepatitis virus B X-associated protein 2 (XAP2), a protein first identified as a co-chaperone protein. TR-XAP2 interactions were TR isoform specific, being observed only with TRb1, and were enhanced by T 3 both in yeast and mammalian cells. Furthermore, small inhibitory RNAmediated knockdown of XAP2 in vitro affected the stability of TRb1. In vivo, siXAP2 abrogated specifically TRb1-mediated (but not TRb2) activation of hypothalamic TRH transcription. This study provides the first in vivo demonstration of a regulatory, physiological role for XAP2.
Methods in molecular biology (Clifton, N.J.), 2008
RNA interference mediated by small interfering RNAs (siRNAs) is a powerful tool for evaluating ge... more RNA interference mediated by small interfering RNAs (siRNAs) is a powerful tool for evaluating gene function in vivo. In particular it should be able to provide tissue-specific and developmental stage-specific knockdown of target genes in physiological contexts. However, there are few demonstrations of its use on neuronal specific genes in vivo. We recently developed a cationic lipid-based approach to study gene function in a neuronal context. In particular, we applied it to study how the novel partner for TRbeta1, hepatitis virus B X-associated protein 2 (XAP2), a protein first identified as a co-chaperone protein, affects T3-transcriptional repression of the hypothalamic gene, TRH. The cationic lipid-based technique used, JetSI/DOPE, was previously shown to efficiently knockdown reporter gene mRNA in vivo. Using JetSI/DOPE to vectorize siRNA against XAP2 mRNA, we show that XAP2 is needed specifically for TRbeta1-mediated (but not TRbeta2) activation of hypothalamic TRH transcripti...
Molecular and Cellular Endocrinology, 2010
Thyroid hormone receptor (TR) and peroxisome proliferator-activated receptor γ (PPARγ) co-regulat... more Thyroid hormone receptor (TR) and peroxisome proliferator-activated receptor γ (PPARγ) co-regulate numerous peripheral metabolic responses. To examine potential crosstalk between PPARγ and TRβ in the hypothalamus, thyrotropin-releasing hormone (Trh) regulation in the newborn mouse hypothalamus was followed. QPCR showed PPARγ to be expressed in the hypothalamus at this developmental stage. Intracerebral injection of PPARγ agonists modified transcription from a TRH-luc
Proceedings of the National Academy of Sciences, 2010
The melanocortin receptor Mc4r, a key relay in leptin signaling, links central energy control to ... more The melanocortin receptor Mc4r, a key relay in leptin signaling, links central energy control to peripheral reserve status. Mc4r activation in different brain areas reduces food intake and increases energy expenditure. Mice lacking Mc4r are obese. Mc4r is expressed by hypothalamic paraventricular thyrotropin-releasing hormone (TRH) neurons and increases energy usage through Trh activation and thyroid hormone (trio-iodothyronine, T 3 ) production. These facts led us to test the hypothesis that energy homoeostasis should require negative feedback by T 3 on Mc4r expression. QPCR and in situ hybridization showed hyperthyroidism to reduce Mc4r mRNA levels in the paraventricular nucleus. Comparative in silico analysis of Mc4r regulatory regions revealed two evolutionarily conserved potential negative thyroid hormone response elements (nTREs). In vivo chromatin immunoprecipitation (ChIP) on mouse hypothalamus demonstrated association of thyroid hormone receptors (TR) with a region spanning one nTRE. Further, in vivo gene reporter assays revealed dose-dependent T 3 repression of transcription from the Mc4r promoter in mouse hypothalamus, in parallel with T 3dependent Trh repression. Mutagenesis of the nTREs in the Mc4r promoter demonstrated direct regulation by T 3 , consolidating the ChIP results. In vivo shRNA knockdown, TR over-expression approaches and use of mutant mice lacking specific TRs, showed that both TRα and TRβ contribute to Mc4r regulation. T 3 repression of Mc4r transcription ensures that the energy-saving effects of T 3 feedback on Trh are not over-ridden by Mc4r activation of Trh. Thus, parallel repression by T 3 on hypothalamic Mc4r and Trh contributes to energy homeostasis.
PLoS ONE, 2014
Mammalian thyroid hormone receptors (TRs) have multiple isoforms, including the bona fide recepto... more Mammalian thyroid hormone receptors (TRs) have multiple isoforms, including the bona fide receptors that bind T 3 (TRa1, TRb1 and TRb2) and a non-hormone-binding variant, TRa2. Intriguingly, TRa2 is strongly expressed in the brain, where its mRNA levels exceed those of functional TRs. Ablation of TRa2 in mice results in over-expression of TRa1, and a complex phenotype with low levels of free T 3 and T 4 , without elevated TSH levels, suggesting an alteration in the negative feedback at the hypothalamic-pituitary level. As the hypothesis of a potential TRH response defect has never been tested, we explored the functional role of TRa2 in negative feedback on transcription of hypothalamic thyrotropin, Trh. The in vivo transcriptional effects of TRa2 on hypothalamic Trh were analysed using an in vivo reporter gene approach. Effects on Trhluc expression were examined to that of two, T 3 positively regulated genes used as controls. Applying in vivo gene transfer showed that TRa2 over-expression in the mouse hypothalamus abrogates T 3 -dependent repression of Trh and T 3 activation of positively regulated promoters, blocking their physiological regulation. Surprisingly, loss of function studies carried out by introducing a shTRa2 construct in the hypothalamus also blocked physiological T 3 dependent regulation. Thus, modulating hypothalamic TRa2 expression by either gain or loss of function abrogated T 3 dependent regulation of Trh transcription, producing constant transcriptional levels insensitive to feedback. This loss of physiological regulation was reflected at the level of the endogenous Trh gene, were gain or loss of function held mRNA levels constant. These results reveal the as yet undescribed dominant negative role of TRa2 over TRa1 effect on hypothalamic Trh transcription.
Molecular and Cellular Endocrinology, 2013
How Retinoid X receptors (RXR) and thyroid hormone receptors (TR) interact on negative TREs and w... more How Retinoid X receptors (RXR) and thyroid hormone receptors (TR) interact on negative TREs and whether RXR subtype specificity is determinant in such regulations is unknown. In a set of functional studies, we analyzed RXR subtype effects in T 3 -dependent repression of hypothalamic thyrotropinreleasing hormone (Trh). Two-hybrid screening of a hypothalamic paraventricular nucleus cDNA bank revealed specific, T 3 -dependent interaction of TRs with RXRb. In vivo chromatin immuno-precipitation showed recruitment of RXRs to the TRE-site 4 region of the Trh promoter in the absence of T 3 . In vivo overexpression of RXRa in the mouse hypothalamus heightened T 3 -independent Trh transcription, whereas RXRb overexpression abrogated this activity. Loss of function of RXRa and b by shRNAs induced inverse regulations. Thus, RXRa and RXRb display specific roles in modulating T 3 -dependent regulation of Trh. These results provide insight into the actions of these different TR heterodimerization partners within the context of a negatively regulated gene.
Molecular and Cellular Endocrinology, 2010
The hypothalamus integrates metabolic and endocrine signals. As such it represents a potential ta... more The hypothalamus integrates metabolic and endocrine signals. As such it represents a potential target for a wide spectrum of endocrine disrupting chemicals (EDCs). We investigated hypothalamic effects of two environmentally abundant xenobiotics, the flame-retardant tetrabromo bisphenol A (TBBPA) and the anti-fouling agent tributyltin (TBT). These EDCs affect endocrine signalling through different nuclear receptors including the thyroid hormone receptor (TR) or its partner, the retinoid X receptor (RXR). Promoter sequences of two hypothalamic genes implicated in metabolic control and regulated by thyroid hormone, thyrotropin-releasing hormone (Trh) and type 4 melanocortin receptor (Mc4r), were studied in vivo using reporter assays. Chronic exposure of gestating dams or acute exposure of their newborns to TBBPA abrogated activation of both Trh and Mc4r transcription. Exposure of lactating dams to TBT amplified activation of Trh without affecting Mc4r transcription. Thus, perinatal exposure to EDCs affecting nuclear receptor signalling modulates hypothalamic set-points controlling metabolic responses.
Journal of Toxicology and Environmental Health, Part B, 2011
Embo Reports, 2006
Transcriptional control of hypothalamic thyrotropin-releasing hormone (TRH) integrates central re... more Transcriptional control of hypothalamic thyrotropin-releasing hormone (TRH) integrates central regulation of the hypothalamohypophyseal-thyroid axis and hence thyroid hormone (triiodothyronine (T 3 )) homeostasis. The two b thyroid hormone receptors, TRb1 and TRb2, contribute to T 3 feedback on TRH, with TRb1 having a more important role in the activation of TRH transcription. How TRb1 fulfils its role in activating TRH gene transcription is unknown. By using a yeast two-hybrid screening of a mouse hypothalamic complementary DNA library, we identified a novel partner for TRb1, hepatitis virus B X-associated protein 2 (XAP2), a protein first identified as a co-chaperone protein. TR-XAP2 interactions were TR isoform specific, being observed only with TRb1, and were enhanced by T 3 both in yeast and mammalian cells. Furthermore, small inhibitory RNAmediated knockdown of XAP2 in vitro affected the stability of TRb1. In vivo, siXAP2 abrogated specifically TRb1-mediated (but not TRb2) activation of hypothalamic TRH transcription. This study provides the first in vivo demonstration of a regulatory, physiological role for XAP2.