Project description:Menopause - when estrogen (E2) levels are decreased - is associated with a loss of skeletal muscle mass and strength. We performed genome-wide expression profiling to identify the underlying mechanisms.
Project description:The female sex hormone estrogens plays a critical role in maintaining muscle mass and muscle stem cell (MuSCs) functions. However, it is still unclear about downstream pathways of estrogens including its receptors that are expressed in both skeletal muscle tissue and MuSCs. To study the specific role of estrogen receptor β (ERβ), one of two main types of estrogen receptors, in skeletal muscle and MuSCs, we generated muscle-specific ERβ-knockout (mKO) mice and muscle stem cell-specific ERβ-knockout (scKO) mice. Here, we show that muscle-specific ERβ-deficient induced decreased muscle strength and fast-type muscle mass in young female mice. Furthermore, muscle stem cell-specific ERβ-deficient young female mice but not male exhibited impaired muscle regeneration ability after acute muscle injury, accompanied by a decreased proliferation rate of muscle stem cells. RNA sequencing analysis showed that the loss of ERβ in muscle stem cells changes the expression of cell cycle associated genes and niche component factors including laminin and collagen. Thus, our characterization of mKO and scKO mice indicate that the estrogen-ERβ pathway is a sex-specific regulatory mechanism that controls both skeletal muscle mass and the proliferation of muscle stem cell in females and could be of importance in a therapeutic context.
Project description:Phosphorylation is important in skeletal muscle development, growth, regeneration, and contractile function. Alterations in the skeletal muscle phosphoproteome due to aging have been reported in males; however, studies in females are lacking. We have demonstrated that estrogen deficiency decreases muscle force which correlates with decreased myosin regulatory light chain phosphorylation. Thus, we questioned whether the decline of estrogen in females that occurs with aging might alter the skeletal muscle phosphoproteome. C57BL/6J female mice randomly assigned to a sham-operated (Sham) or ovariectomy (Ovx) group to investigate the effects of estrogen deficiency on skeletal muscle protein phosphorylation in a resting, non-contracting condition. After 16 weeks of estrogen deficiency, the tibialis anterior muscle was dissected and prepped for label-free nano-liquid chromatography tandem mass spectrometry phosphoproteomic analysis. We identified 4,780 phosphopeptides in tibialis anterior muscles of ovariectomized (Ovx) and Sham-operated (Sham) control mice. Further analysis revealed 647 differentially regulated phosphopeptides (Benjamini – Hochberg adjusted p-value < 0.05 and 1.5-fold change ratio) that corresponded to 130 proteins with 22 proteins differentially phosphorylated (3 unique to Ovx, two unique to Sham, six upregulated, and 11 downregulated). Differentially phosphorylated proteins associated with the sarcomere, cytoplasm, and metabolic and calcium signaling pathways were identified. Our work provides the first global phosphoproteomic analysis in females and how estrogen deficiency impacts the skeletal muscle phosphoproteome.
Project description:The loss of skeletal muscle strength mid-life in females is associated with the decline of estrogen. Here, we questioned how estrogen deficiency might impact the overall skeletal muscle phosphoproteome after contraction, as force production induces phosphorylation of several muscle proteins. Phosphoproteomic analyses of the tibialis anterior muscle after contraction in two mouse models of estrogen deficiency, ovariectomy (Ovariectomized [Ovx] vs Sham) and natural aging-induced ovarian senescence (Older Adult [OA] vs Young Adult [YA]), identified a total of 2,593 and 3,507 phosphopeptides in Ovx/Sham and OA/YA datasets, respectively. Further analysis of estrogen deficiency-associated proteins and phosphosites identified 66 proteins and 21 phosphosites from both datasets. Of these, 4 estrogen deficiency-associated proteins and 4 estrogen deficiency-associated phosphosites were significant and differentially phosphorylated or regulated, respectively. Comparative analyses between Ovx/Sham and OA/YA using Ingenuity Pathway Analysis (IPA) found parallel patterns of inhibition and activation across IPA-defined canonical signaling pathways and physiological functional analysis, which were similarly observed in downstream GO, KEGG, and Reactome pathway overrepresentation analysis pertaining to muscle structural integrity and contraction, including AMPK and calcium signaling. IPA Upstream regulator analysis identified MAPK1 and PRKACA as candidate kinases and calcineurin as a candidate phosphatase sensitive to estrogen. Our findings highlight key molecular signatures and pathways in contracted muscle suggesting that the similarities identified across both datasets could elucidate molecular mechanisms that may contribute to skeletal muscle strength loss due to estrogen deficiency.
Project description:Tamoxifen, a selective estrogen receptor modulator (SERM), is commonly used in the treatment of hormone-responsive cancers. The effects of tamoxifen in anabolic tissues harboring estrogen-receptors, such as skeletal muscle, are poorly understood. As estrogen and estrogen receptors play an important role in skeletal muscle development and repair, we hypothesize that tamoxifen may have specific effects on myogenesis, the developmental process underlying muscle cells differentiation and repair. Myogenesis is characterized by fine-tuned changes in protein expression as embryonic myoblasts and adult satellite cells transition from pluripotent stem cells to multinucleated, contractile muscle fibers: we undertake a quantitative proteomic analysis of tamoxifen-induced changes in developing skeletal muscle cells which we expect may also shed light on the effect of tamoxifen on muscle repair.
We report a tandem mass-tag (TMT) approach to tamoxifen-treated myogenesis in C2C12 cells, a well-characterized model of in vitro murine skeletal muscle differentiation. A longitudinal analysis of >10,000 proteins identified in C2C12 myogenesis revealed a novel subset of 1,239 myogenically-regulated proteins. This set of regulatory proteins clustered into five distinct longitudinal expression trends which significantly overlap those obtained in similar analyses performed in human myocytes. A longitudinal analysis of myogenesis in the presence of tamoxifen, when contrasted with a similar analysis in untreated myogenesis finds that while the vast majority of myogenically-regulated proteins were unaffected by tamoxifen treatment, specific pathways and networks are affected. We document a specific functional enrichment for adiponectin-signaling, whereby a set of 198 proteins were differentially expressed relative to controls at one or more stages of myogenesis, the majority of which were involved in steroid biosynthesis, lipid storage and/or metal ion homeostasis. Interestingly, the only protein that was differentially expressed in the tamoxifen-treated cells at every stage of myogenesis was metallothionein-1 (MT1). Elevated levels of MT1 have been correlated with tamoxifen resistance and increased patient mortality and relapse in breast cancer, as well as with cachexia and muscle atrophy in rodent models. Increased MT1 expression levels may contribute to the musculoskeletal effects reported by patients undergoing tamoxifen treatment. Finally, we present a powerful, self-validating pipeline for analyzing the total proteomic response to in vitro treatment across every stage of muscle cells development which can be easily adapted to study the effects of other drugs on myogenesis.
Project description:Analysis of gene expression profiles in skeletal muscle tissue after long-term use of HRT. Networks of enriched processes in skeletal muscle responding to long-term use of estrogen-based HRT in comparison with women without any HRT in a genetically controlled setting were contructed. The association between the expression of specific biological processes and muscle composition or performance was tested. The hypothesis was that the differences in gene expression profiles reflect the known differences in muscle composition and performance. Total RNA obtained from muscle biopsies (vastus lateralis) from genetically identical female twin pairs (n=11 pairs) of which one sister is a user of postmenopausal, estrogen-based HRT (n=11), while the other is a never-user (n=11).
Project description:Modification of Gene Expression of Skeletal Muscle in Response to postmenopause with or without Hormone Replacement Therapy. Even though menopause is often accompanied with first signs of age-associated changes in muscle structure and function, the effects of hormone replacement therapy (HRT) or menopause-related decline in estrogen production in the muscles of postmenopausal women is not well understood. We have used a randomized double-blinded study design together with an explorative microarray experiment to characterize possible effects of continuous, combined HRT and estrogen deprivation on the skeletal muscle of fifteen early postmenopausal women from which 10 used HRT and 5 used placebo for 12-months in a douple-blinded design. Keywords: time course analysis from HRT users and non-users comparison of gene expression in skeletal muscle of healthy postmenopausel women using HRT (n=10) vs not-using HRT (n=5)
Project description:Analysis of gene expression profiles in skeletal muscle tissue after long-term use of HRT. Networks of enriched processes in skeletal muscle responding to long-term use of estrogen-based HRT in comparison with women without any HRT in a genetically controlled setting were contructed. The association between the expression of specific biological processes and muscle composition or performance was tested. The hypothesis was that the differences in gene expression profiles reflect the known differences in muscle composition and performance.