Effect of Gadd45a overexpression on mouse skeletal muscle mRNA levels.
Ontology highlight
ABSTRACT: 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.
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:ATF4 is a bZIP transcription factor that that promotes skeletal muscle atrophy. The goal of these studies was to determine the effects of ATF4 overexpression on mRNA levels in differentiated C2C12 myotubes. For additional details see Ebert et al, Stress-Induced Skeletal Muscle Gadd45a Expression Reprograms Myonuclei and Causes Muscle Atrophy. JBC epub. June 12,2012 C2C12 myotubes were infected with adenovirus co-expressing eGFP and ATF4-FLAG. Control myotubes were infected with adenovirus co-expressing eGFP and a transcriptionally inactive ATF4 construct (ATF4∆bZIP).
Project description:Muscle denervation causes skeletal muscle atrophy. The goal of these studies was to determine the effects of denervation on skeletal muscle mRNA levels in C57BL/6 mice. For additional details see Ebert et al, Stress-Induced Skeletal Muscle Gadd45a Expression Reprograms Myonuclei and Causes Muscle Atrophy. JBC epub. June 12, 2012. Left sciatic nerves of C57BL/6 mice were transected. Seven days later bilateral tibialis anterior muscles were harvested. mRNA levels in denervated muscles were normalized to levels in contralateral innervated muscles.
Project description:To investigate the role of the circadian clock gene Bmal1 in skeletal muscle, we compared the circadian transcriptomes of fast tibialis anterior (TA) and slow soleus (SOL) skeletal muscles from muscle-specific Bmal1 KO (mKO) and their control Cre- littermates (Ctrl). Keyword: Circadian Transcriptome, time course 72 samples were analyzed, comprised of 4 experimental groups (Ctrl SOL, mKO SOL, Ctrl TA, mKO TA), with 3 biological replicates for each time point sampled every 4 hours for 24 hours. SOL and TA muscles were collected from the same animals, as indicated by Source Animal ID data column
Project description:Skeletal muscle atrophy is a highly prevalent and debilitating condition that remains poorly understood at the molecular level. Previous work found that skeletal muscle atrophy involves activating transcription factor 4 (ATF4), a protein in the basic leucine zipper (bZIP) transcription factor family. However, the direct biochemical mechanism by which ATF4 promotes muscle atrophy was unknown. Because bZIP proteins such as ATF4 must dimerize to bind and activate genes, and because ATF4 is unable to form highly stable homodimers, we hypothesized that ATF4 may promote muscle atrophy by heterodimerizing with another bZIP family member. To test this hypothesis, we biochemically isolated skeletal muscle proteins that associate with the dimerization- and DNA-binding domain of ATF4 (the bZIP domain) in mouse skeletal muscle fibers in vivo. Interestingly, we found that ATF4 makes up one half of at least 5 distinct heterodimeric bZIP transcription factors in skeletal muscle fibers. This three-way interaction between ATF4, C/EBPbeta and the ATF4-C/EBP composite site activates the Gadd45a gene, which encodes a known mediator of muscle atrophy (Gadd45a). Together, these results identify a direct biochemical mechanism by which ATF4 induces skeletal muscle atrophy and provide new insight into the way that skeletal muscle atrophy occurs at the molecular level.
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.
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:MuRF1 is a muscle-specific E3 ubiquitin ligase and component of the ubiquitin proteasome system. MuRF1 is transcriptionally upregulated under conditions that cause muscle loss, in both rodents and humans, and is a recognized marker of muscle atrophy. In this study, we used in vivo electroporation to determine if MuRF1 overexpression alone can cause muscle atrophy and, in combination with ubiquitin proteomics, identify the endogenous MuRF1 substrates in skeletal muscle. Tibialis anterior (TA) muscles were transfected with an untagged MuRF1 plasmid or control plasmid for 14 days. A total of 963 ubiquitination sites, corresponding to 250 proteins, were quantified from the TA muscle. Statistical analysis revealed that the overexpression of MuRF1 resulted in significant upregulation of 153 ubiquitination sites on 45 proteins and significant downregulation of 16 sites on 11 proteins. Substrates of MuRF1 include contractile and metabolic proteins, deubiquitinases, p62, and VCP. Moreover, MuRF1-mediated ubiquitination leads to destabilization and breakdown of the sarcomere and reveals a role for MuRF1 in the regulation of additional proteolytic pathways in skeletal muscle.
Project description:ATF4 is a bZIP transcription factor that that promotes skeletal muscle atrophy. The goal of these studies was to determine the effects of ATF4 overexpression on mRNA levels in differentiated C2C12 myotubes. For additional details see Ebert et al, Stress-Induced Skeletal Muscle Gadd45a Expression Reprograms Myonuclei and Causes Muscle Atrophy. JBC epub. June 12,2012
Project description:The goal of these studies was to determine the effects of fasting on skeletal muscle mRNA levels in healthy human subjects. Seven healthy adult human subjects fasted for 40 hours and then a muscle biopsy (fasting sample) was obtained from the vastus lateralis muscle. Immediately after the first muscle biospy, subjects then ate a mixed meal. Six hours after the first muscle biopsy, a second muscle biopsy (fed sample) was obtained from the contralateral vastus lateralis muscle. In each subject, mRNA levels under fasting conditions were normalized to mRNA levels under fed conditions, which were set at 1.