Project description:To investigate the roles of ATF4 in skeletal muscle aging we generated muscle-specific ATF4 knockout (ATF4 mKO) mice. We then performed gene expression profiling analysis using data obtained from RNA-seq of tibialis anterior muscles at 6-months and 22-months of age.
Project description:For additional details see Ebert et al, Identification and Small Molecule Inhibition of an ATF4-dependent Pathway to Age-related Skeletal Muscle Weakness and Atrophy. Quadriceps femoris muscles were harvested from 22-month-old muscle-specfic ATF4 knockout (ATF4 mKO) mice and littermate controls. mRNA levels in ATF4 mKO muscles were normalized to levels in littermate control muscles.
Project description:ATF4 is a fasting-induced trascription factor that promotes skeletal muscle atrophy. The goal of these studies was to determine how of loss of ATF4 affects skeletal muscle mRNA expression. For additional details see Ebert et al, Stress-Induced Skeletal Muscle Gadd45a Expression Reprograms Myonuclei and Causes Muscle Atrophy. JBC epub. June 12, 2012. Muscle-specfic ATF4 knockout (ATF4 mKO) mice and littermate controls were fasted for 24 hours and then tibialis anterior muscles were harvested. mRNA levels in ATF4 mKO muscles were normalized to levels in littermate control muscles.
Project description:p53 regulates a distinct subset of skeletal muscle mRNAs during immobilization-induced skeletal muscle atrophy For additional details see Fox et al, p53 and ATF4 mediate distinct and additive pathways to skeletal muscle atrophy during limb immobilization. Am J Physiol Endocrinol Metab. 2014 Aug 1;307(3):E245-61. Bilateral tibialis anterior muscles were harvested at three days for the following conditions: 1) hindlimb immobilization of C57BL/6 mice; 2) hindlimb immobilization of p53 mKO and littermate control mice; 3) transfection of wild type mice with p53 plasmid or control plasmid
Project description:Studying the molecular basis for the skeletal muscle mitochondrial stress response could potentially be targeted to counteract metabolic disorders such as obesity. We uncovered a crucial role for the mitochondrial protease LONP1 in controlling the muscle mitochondrial proteostasis stress response that governs systemic metabolic homeostasis. Skeletal muscle-specific ablation of LONP1 led to broad genomic reprogramming of muscle and protected the mice from HFD-induced obesity. To thoroughly analyze pathways that are affected by ATF4 deficiency in the context of LONP1 mKO, we performed RNA-Seq transcriptome analysis of skeletal muscles from WT, LONP1 mKO and LONP1ATF4 DmKO mice. We identified a total of 3017 differentially expressed genes with a cutoff of 1.5-fold, and p < 0.05. Surprisingly, we found that ATF4 loss blunted a subset of regulated genes in LONP1 mKO muscles, whereas the majority of differentially regulated genes in LONP1 mKO muscles were not affected by ATF4 ablation. GO analysis of ATF4-dependent genes regulated by LONP1 ablation revealed significant enrichment in amino acid metabolic processes, Interestingly, however, LONP1 deficiency induced activation of muscle UPR and UPR-related RNA processing as well as myokine pathways were not affected by ATF4 ablation. Therefore, our results highlight a ATF4-independent mechanism in mediating the UPRmt in mammals.
Project description:To understand the role of LSD1 in transcriptional regulation in muscle under voluntary wheel running (VWR) training, RNA-seq analyses of soleus muscles of skeletal muscle-specific LSD1 KO mice (LSD1-mKO mice) and WT mice after VWR were carried out. We found that loss of LSD1 led to increased expression of oxidative metabolism genes in soleus muscle.
Project description:To understand the role of LSD1 in transcriptional regulation in muscle under glucocorticoid stress, RNA-seq analyses of gastrocnemius and soleus muscles of skeletal muscle-specific LSD1 KO mice (LSD1-mKO mice) and WT mice after dexamethasone were carried out. We found that LSD1 inhibition led to increased expression of muscle atrophy associated genes and slow fiber genes in gastrocnemius muscle but not in soleus muscle.
Project description:For additional details see Ebert et al, Identification and Small Molecule Inhibition of an ATF4-dependent Pathway to Age-related Skeletal Muscle Weakness and Atrophy.
Project description:Age-related skeletal muscle atrophy is a debilitating condition that has significant negative impacts on health and quality of life. Despite broad clinical impact, the molecular basis of age-related skeletal muscle atrophy is not well understood. Here, we determined protein turnover rates in skeletal muscle of 22-month-old control mice and 22-month-old muscle-specific ATF4 knockout (ATF4 mKO) mice, which are partially resistant to age-related muscle atrophy. All samples were analyzed by DDA TripleTOF 6600 mass spectrometer for downstream analysis of protein turnover. Quantitative MS1 peak areas were extracted from DDA raw files in the Skyline-Daily software platform. ProteinPilot search results were imported into the Skyline software to build a spectral library, followed by import of raw MS files for extraction of chromatographic peak areas. A custom skyline report containing all peptide and protein characteristics, annotations, and quantitative information including isotopologue peak areas was exported and used for downstream analysis and calculation of protein turnover rates in R using in-house R scripts (TurnoveR tool). Precursor-pool corrected protein turnover rates were calculated using the same approach employed in previous studies using the Topograph software platform. For calculation of protein abundance changes, DIA acquisitions from six samples (3 ATF4 KO and 3 WT samples) were quantitatively processed using Spectronaut v14. Analysis of protein turnover indicates that most proteins with altered turnover rates in ATF4 mKO muscles have decreased half-lives and are components of the mitochondrion. These proteins include subunits of the ATP Synthase (Atp5b, Atp5o), Ubiquinol-Cytochrome C Reductase (Uqcrc1, Uqcrh) and Cytochrome C Oxidase (Cox6b1) complexes, among others. These findings implicate increased rates of mitochondrial protein turnover as a mechanism that underlies, at least in part, the protection from age-induced muscle atrophy in ATF4 mKO mice.
Project description:Gadd45a is a stress-induced protein that causes skeletal muscle atrophy. The goal of these studies was to determine the effects of Gadd45a overexpression on mRNA levels in mouse skeletal muscle. For additional details see Ebert et al, Stress-Induced Skeletal Muscle Gadd45a Expression Reprograms Myonuclei and Causes Muscle Atrophy. JBC epub. June 12, 2012. Tibialis anterior (TA) muscles from muscle-specfic ATF4 knockout mice (ATF4 mKO) were transfected with either 20 mg empty plasmid (pcDNA3) (left TA) or 20 mg pCMV-FLAG-Gadd45a (right TA) and harvested 7 days later. mRNA levels in Gadd45a-transfected muscles were normalized to levels in control transfected muscles.