Project description:Expansion of a polyglutamine (polyQ) tract in the gene for the androgen receptor (AR) results in partial loss of transactivation function and causes spinobulbar muscular atrophy (SBMA). Modification of AR by small ubiquitin-like modifier (SUMO) reduces AR function in a promoter context-dependent manner. We used microarrays to confirm and demonstrate loss of AR function from polyQ expansion and to test the degree to which AR function is altered by preventing polyQ AR SUMOylation.
Project description:Expansion of a polyglutamine (polyQ) tract in the gene for the androgen receptor (AR) results in partial loss of transactivation function and causes spinobulbar muscular atrophy (SBMA). Modification of AR by small ubiquitin-like modifier (SUMO) reduces AR function in a promoter context-dependent manner. We used microarrays to confirm and demonstrate loss of AR function from polyQ expansion and to test the degree to which AR function is altered by preventing polyQ AR SUMOylation. PC12 cells expressing AR10Q, AR112Q, or nonSUMOylatable AR112Q (KRKR) in the presence or absence of synthetic androgen R1881 were assessed for alterations in AR function by comparing gene expression changes with each AR variant in response to ligand.
Project description:Spinobulbar muscular atrophy (SBMA) is a neurodegenerative disease caused by expansion of a polyglutamine tract in the androgen receptor (AR). This mutation confers toxic function to AR through unknown mechanisms. Mutant AR toxicity requires binding of its hormone ligand, suggesting that pathogenesis involves ligand-induced changes in AR. However, whether toxicity is mediated by native AR function or a novel AR function is unknown. We systematically investigated events downstream of ligand-dependent AR activation in a Drosophila model of SBMA. We show that nuclear translocation of AR is necessary but not sufficient for toxicity and that DNA binding by AR is necessary for toxicity. Mutagenesis studies demonstrated that a functional AF-2 domain is essential for toxicity, a finding corroborated by a genetic screen that identified AF-2 interactors as dominant modifiers of degeneration. These findings indicate that SBMA pathogenesis is mediated by misappropriation of native protein function, a mechanism that may apply broadly to polyglutamine diseases. We used Affymetrix arrays to generate a molecular phenotype of degeneration in profile flies expressing wild-type or polyglutamine-expanded AR. We also expressed in the fly eye polyglutamine-expanded AR with point mutations affecting the DNA binding domain and the AF-2 domain. In some experiments, GMR-GAL4; UAR-AR flies were crossed to flies carrying a chromosomal duplication of the limpet gene. Transgene expression was induced in the eye using GMR-GAL4. Flies were crossed at 29 deg C on food containing either 1mM DHT or 1% ethanol (vehicle).
Project description:Spinobulbar muscular atrophy (SBMA) is a neurodegenerative disease caused by expansion of a polyglutamine tract in the androgen receptor (AR). This mutation confers toxic function to AR through unknown mechanisms. Mutant AR toxicity requires binding of its hormone ligand, suggesting that pathogenesis involves ligand-induced changes in AR. However, whether toxicity is mediated by native AR function or a novel AR function is unknown. We systematically investigated events downstream of ligand-dependent AR activation in a Drosophila model of SBMA. We show that nuclear translocation of AR is necessary but not sufficient for toxicity and that DNA binding by AR is necessary for toxicity. Mutagenesis studies demonstrated that a functional AF-2 domain is essential for toxicity, a finding corroborated by a genetic screen that identified AF-2 interactors as dominant modifiers of degeneration. These findings indicate that SBMA pathogenesis is mediated by misappropriation of native protein function, a mechanism that may apply broadly to polyglutamine diseases.
Project description:Effects of polyglutamine expansion and subcellular localization of C-terminal fragment of Cav2.1 in PC12 rat pheochromocytoma cells
Project description:The goal of this study was to determine the mechanism of androgne in driving muscle hypertrophy programmes. CONCLUSION: AR transcriptionally cooperates with SMAD4 and this affect is lost in the presence of expansion of the polyglutamine repeat in the AR gene.
Project description:Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disorder caused by a polyglutamine expansion in the androgen receptor (AR). Previous studies have shown that transcriptional dysregulation and mitochondrial impairment occur in SBMA. We used gene-expression analysis and ChIP-sequencing to map transcriptional changes in SBMA induced pluripotent stem cell-derived motor neurons. The SBMA cells had decreased expression of genes encoding electron transport chain subunits and other metabolic proteins, associated with reduced histone acetylation which may be contributing to mitochondrial dysfunction. AR ChIP-sequencing results indicate that this is not a direct transcriptional effect of mutant AR on mitochondrial gene expression. Furthermore, we found decreased acetyl-CoA, and pyruvate supplementation to correct this deficiency improved mitochondrial function and SBMA motor neuron viability. We propose that epigenetic dysregulation of metabolic genes contributes to reduced mitochondrial ATP production. Our results show a molecular link between altered epigenetic regulation and mitochondrial metabolism that contributes to neurodegeneration.
Project description:Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disorder caused by a polyglutamine expansion in the androgen receptor (AR). Previous studies have shown that transcriptional dysregulation and mitochondrial impairment occur in SBMA. We used gene-expression analysis and ChIP-sequencing to map transcriptional changes in SBMA induced pluripotent stem cell-derived motor neurons. The SBMA cells had decreased expression of genes encoding electron transport chain subunits and other metabolic proteins, associated with reduced histone acetylation which may be contributing to mitochondrial dysfunction. AR ChIP-sequencing results indicate that this is not a direct transcriptional effect of mutant AR on mitochondrial gene expression. Furthermore, we found decreased acetyl-CoA, and pyruvate supplementation to correct this deficiency improved mitochondrial function and SBMA motor neuron viability. We propose that epigenetic dysregulation of metabolic genes contributes to reduced mitochondrial ATP production. Our results show a molecular link between altered epigenetic regulation and mitochondrial metabolism that contributes to neurodegeneration.