5 research outputs found
Analyses à l'échelle du génome des voies de signalisation contrÎlées par les récepteurs stéroïdiens
Androgens (ADs) and glucocorticoids (GCs) are steroid hormones exerting pleiotropic effects in mammals. Their effects are mediated by two nuclear receptors, the androgen (AR) and the glucocorticoid (GR) receptor, respectively. Although GCs are extensively used to treat inflammatory diseases and antiandrogens for prostate cancer, long-term treatments induce major side effects such as muscle atrophy.To determine the mechanisms underlying their effects in muscle, we performed phenotypic, transcriptomic and cistromic analyses. The first part of this work demonstrates that myofiber GR negatively controls muscle mass and strength under physiological GCs levels. GR loss in skeletal muscle did not affect catabolic pathways, but enhanced the expression of anabolic factors and reduced that of anti-anabolic ones. We also showed that myofiber GR binds DNA to GR response elements (GREs) located at enhancers, in association with Myod1 and Foxf2, and interact with promoter-bound factors such as Nrf1 to promote gene transcription.In the second part of this work, we compared GR cistromes and transcriptomes in prostate and skeletal muscle, and identified binding sites for additional transcription factors in the vicinity of GREs, indicating that they contribute to the tissue specificity. In addition, by comparing the AR and GR cistromes and transcriptomes in prostate, we show that the response elements bound by both receptors are distinct from those bound by either AR or GR, and that the receptor-selectivity depends mostly on the surrounding factors.Finally, we compared transcriptomic and epigenetic data of skeletal muscle tissue and C2C12 myoblasts and myotubes and provide a detailed description of genes, signaling pathways and transcription factors that are differentially expressed during myogenic differentiation.In conclusion, our work allowed to clarify the molecular mechanisms regulating muscle homeostasis and provides the basis of a molecular understanding of tissue- and/or promoter-specific activity of ADs and GCs.Les androgens(ADs) et les glucocorticoĂŻdes (GCs) sont des hormones stĂ©roĂŻdiennes qui exercent des effets plĂ©iotropes chez les mammifĂšres. Leurs effets sont relayĂ©s par deux rĂ©cepteurs nuclĂ©aires, le rĂ©cepteur des androgĂšnes (AR) et le rĂ©cepteur des glucocorticoĂŻdes (GR), respectivement. MĂȘme si les GCs sont frĂ©quemment utilisĂ©s pour traiter les maladies inflammatoires et les antiandrogĂšnes pour le cancer de la prostate, les traitements Ă long terme induisent des effets secondaires majeurs, notamment l'atrophie musculaire.Afin de prĂ©ciser les mĂ©canismes dâaction de ces hormones, nous avons rĂ©alisĂ© des analyses phĂ©notypiques, transcriptomiques et cistromiques. La premiĂšre partie de ce travail dĂ©montre que GR des myofibres contrĂŽle nĂ©gativement la masse et la force musculaire aux niveaux physiologiques de GCs. La perte de GR dans les muscles squelettiques n'affecte pas les voies cataboliques, mais augmente lâexpression de facteurs anaboliques et rĂ©duit celle de facteurs anti-anaboliques. Nous avons Ă©galement montrĂ© que GR se lie Ă des Ă©lĂ©ments de rĂ©ponse du GR (GREs) situĂ©s aux enhancers, en association avec Myod1 et Foxf2, et interagit avec des facteurs liĂ©s aux promoteurs, tels que Nrf1, pour favoriser la transcription des gĂšnes.Dans la deuxiĂšme partie de ce travail, nous avons comparĂ© le cistrome et le transcriptome du GR dans la prostate et le muscle squelettique, et identifiĂ© des sites de liaison pour d'autres facteurs de transcription proche des GREs, indiquant que ces facteurs contribuent Ă la spĂ©cificitĂ© tissulaire. De plus, en comparant les cistromes et transcriptomes dâAR et de GR dans la prostate, nous montrons que les Ă©lĂ©ments de rĂ©ponse liĂ©s par les deux rĂ©cepteurs sont distincts de ceux liĂ©s uniquement par AR ou GR, et que la sĂ©lectivitĂ© du rĂ©cepteur dĂ©pend de la liaison dâautres facteurs de transcription.Enfin, nous avons comparĂ© les donnĂ©es transcriptomiques et Ă©pigĂ©nĂ©tiques du tissu musculaire squelettique et de myoblastes et myotubes C2C12, et nous fournissons une description dĂ©taillĂ©e de gĂšnes, voies de signalisation et facteurs de transcription exprimĂ©s de façon diffĂ©rentielle pendant la diffĂ©renciation myogĂ©nique.En conclusion, nos travaux ont permis de clarifier les mĂ©canismes molĂ©culaires rĂ©gulant l'homĂ©ostasie musculaire et ont Ă©tabli la base d'une comprĂ©hension molĂ©culaire des effets spĂ©cifiques des ADs et des GCs dans divers types cellulaires
Cytosolic sequestration of the vitamin D receptor as a therapeutic option for vitamin D-induced hypercalcemia
International audienceThe bioactive vitamin D3, 1α,25(OH)2D3, plays a central role in calcium homeostasis by controlling the activity of the vitamin D receptor (VDR) in various tissues. Hypercalcemia secondary to high circulating levels of vitamin D3 leads to hypercalciuria, nephrocalcinosis and renal dysfunctions. Current therapeutic strategies aim at limiting calcium intake, absorption and resorption, or 1α,25(OH)2D3 synthesis, but are poorly efficient. In this study, we identify WBP4 as a new VDR interactant, and demonstrate that it controls VDR subcellular localization. Moreover, we show that the vitamin D analogue ZK168281 enhances the interaction between VDR and WBP4 in the cytosol, and normalizes the expression of VDR target genes and serum calcium levels in 1α,25(OH)2D3-intoxicated mice. As ZK168281 also blunts 1α,25(OH)2D3-induced VDR signaling in fibroblasts of a patient with impaired vitamin D degradation, this VDR antagonist represents a promising therapeutic option for 1α,25(OH)2D3-induced hypercalcemia
Single-cell analyses unravel cell typeâspecific responses to a vitamin D analog in prostatic precancerous lesions
International audienc
Androgen receptor coordinates muscle metabolic and contractile functions
Abstract Background Androgens are anabolic steroid hormones that exert their function by binding to the androgen receptor (AR). We have previously established that AR deficiency in limb muscles impairs sarcomere myofibrillar organization and decreases muscle strength in male mice. However, despite numerous studies performed in men and rodents, the signalling pathways controlled by androgens via their receptor in skeletal muscles remain poorly understood. Methods Male ARskmâ/y (n = 7â12) and female ARskmâ/â mice (n = 9), in which AR is selectively ablated in myofibres of musculoskeletal tissue, and male AR(i)skmâ/y, in which AR is selectively ablated in postâmitotic skeletal muscle myofibres (n = 6), were generated. Longitudinal monitoring of body weight, blood glucose, insulin, lipids and lipoproteins was performed, alongside metabolomic analyses. Glucose metabolism was evaluated in C2C12 cells treated with 5αâdihydrotestosterone (DHT) and the antiâandrogen flutamide (n = 6). Histological analyses on macroscopic and ultrastructural levels of longitudinal and transversal muscle sections were conducted. The transcriptome of gastrocnemius muscles from control and ARskmâ/y mice was analysed at the age of 9 weeks (P < 0.05, 2138 differentially expressed genes) and validated by RTâqPCR analysis. The AR (4691 peaks with false discovery rate [FDR] < 0.1) and H3K4me2 (47 225 peaks with FDR < 0.05) cistromes in limb muscles were determined in 11âweekâold wildâtype mice. Results We show that disrupting the androgen/AR axis impairs in vivo glycolytic activity and fastens the development of type 2 diabetes in male, but not in female mice. In agreement, treatment with DHT increases glycolysis in C2C12 myotubes by 30%, whereas flutamide has an opposite effect. Fatty acids are less efficiently metabolized in skeletal muscles of ARskmâ/y mice and accumulate in cytoplasm, despite increased transcript levels of genes encoding key enzymes of betaâoxidation and mitochondrial content. Impaired glucose and fatty acid metabolism in ARâdeficient muscle fibres is associated with 30% increased lysine and branchedâchain amino acid catabolism, decreased polyamine biosynthesis and disrupted glutamate transamination. This metabolic switch generates ammonia (2âfold increase) and oxidative stress (30% increased H2O2 levels), which impacts mitochondrial functions and causes necrosis in <1% fibres. We unravel that AR directly activates the transcription of genes involved in glycolysis, oxidative metabolism and muscle contraction. Conclusions Our study provides important insights into diseases caused by impaired AR function in musculoskeletal system and delivers a deeper understanding of skeletal muscle pathophysiological dynamics that is instrumental to develop effective treatment for muscle disorders
Myod1 and GR coordinate myofiber-specific transcriptional enhancers
International audienceSkeletal muscle is a dynamic tissue the size of which can be remodeled through the concerted actions of various cues. Here, we investigated the skeletal muscle transcriptional program and identified key tissue-specific regulatory genetic elements. Our results show that Myod1 is bound to numerous skeletal muscle enhancers in collaboration with the glucocorticoid receptor (GR) to control gene expression. Remarkably, transcriptional activation controlled by these factors occurs through direct contacts with the promoter region of target genes, via the CpG-bound transcription factor Nrf1, and the formation of Ctcfanchored chromatin loops, in a myofiber-specific manner. Moreover, we demonstrate that GR negatively controls muscle mass and strength in mice by down-regulating anabolic pathways. Taken together, our data establish Myod1, GR and Nrf1 as key players of muscle-specific enhancer-promoter communication that orchestrate myofiber size regulation