Project description:We performed gene expression profiling by microarray using RNA extracted from the tibialis anterior of control and Hira myofiber-specific conditional knockout mice at 6 months of age. Hira is a histone chaperone responsible for replication-independent incorporation of histone variant H3.3 at actively transcribed loci. Conditional knockout of Hira in myofibers improved strength and endurance, caused hypertrophy and regeneration, and increased the percentage of type I fibers. These results illustrate the physiological consequences of disrupting Hira-mediated chromatin assembly in myofibers.
Project description:We performed gene expression profiling by microarray using RNA extracted from the tibialis anterior of control and Hira myofiber-specific conditional knockout mice at 6 weeks of age. Hira is a histone chaperone responsible for replication-independent incorporation of histone variant H3.3 at actively transcribed loci. Conditional knockout of Hira in myofibers caused hypertrophy, degeneration, and increased the percentage of type I fibers. These results illustrate the physiological consequences of disrupting Hira-mediated chromatin assembly in myofibers.
Project description:We performed gene expression profiling by microarray using RNA extracted from healthy free wall left ventricle tissues from control and Hira cardiomyocyte-specific conditional knockout mice at 6 weeks of age. Hira is a histone chaperone responsible for replication-independent incorporation of histone variant H3.3 at actively transcribed regions. Conditional knockout of Hira in cardiomyocytes resulted in impaired cardiac function, cardiomyocyte degeneration and focal replacement fibrosis. These results illustrate the role of Hira in controlling the cardiac gene program. 4 animals per group (control and Hira conditional knockout) hybridized in triplicate. RNA was extracted from healthy free wall left ventricle.
Project description:We performed gene expression profiling by microarray using RNA extracted from healthy free wall left ventricle tissues from control and Hira cardiomyocyte-specific conditional knockout mice at 6 weeks of age. Hira is a histone chaperone responsible for replication-independent incorporation of histone variant H3.3 at actively transcribed regions. Conditional knockout of Hira in cardiomyocytes resulted in impaired cardiac function, cardiomyocyte degeneration and focal replacement fibrosis. These results illustrate the role of Hira in controlling the cardiac gene program.
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:This study aims to characterize the diversity of cell types in human skeletal muscle across age using two complementary technologies: single-cell and single-nucleus sequencing, which provide a comprehensive coverage of cell types in the muscle. We leveraged the aforementioned datasets to study change in cell type composition and gene expression between young (n= 8, approx. 20-40 yrs) and old (n = 9, approx. 60-80 yrs) adults, highlighting changes in the major skeletal muscle compartments, muscle satellite cells, myofiber and muscle microenvironment including stromal, immune and vascular cell types. Additionally, we generated a complementary mouse muscle aging dataset by profiling hindlimb muscles from young (n = 5, 3 months) versus old mice (n = 3, 19 months), using single-cell and single-nucleus sequencing for comparison.
Project description:Sarcopenia is a degenerative condition that consists in the age-induced atrophy and functional decline of skeletal muscle cells (myofibers). A common hypothesis is that inducing myofiber hypertrophy should also reinstate myofiber contractile function but such model has not been extensively tested. Here, we find that the levels of the ubiquitin ligase UBR4 increase in skeletal muscle with aging, and that muscle-specific UBR4 loss rescues age-associated myofiber atrophy in mice. However, UBR4 promotes proteolysis by the proteasome and consequently UBR4 loss reduces the muscle specific force and accelerates the decline in muscle protein quality that occurs with aging in mice. Similarly, hypertrophic signaling induced via muscle-specific loss of UBR4 and of several other ubiquitin ligases consistently compromises muscle function and shortens lifespan in Drosophila by reducing protein quality control. Altogether, these findings indicate that ubiquitin ligases regulate in opposite fashion myofiber size and muscle protein quality control during aging.
Project description:Analysis of skeletal muscles with specific knockout (KO) of Phosphatase and tensin homolog (Pten) gene in an animal model of DMD (mdx mice). Pten knockout alleviates myofiber degeneration and restores muscle function in mdx mice.
Project description:GRSF1 is a mitochondrial RNA-binding protein important for maintaining mitochondrial function. We found that GRSF1 is highly expressed in cultured skeletal myoblasts differentiating into myotubes. To understand the physiological function of GRSF1 in vivo, we generated mice in which GRSF1 was specifically ablated in skeletal muscle. The conditional knockout mice (Grsf1cKO) appeared normal until 7-9 months of age. Importantly, however, a reduction of muscle endurance compared to wild-type controls was observed in 16- to18-month old Grsf1cKO mice. Transcriptomic analysis revealed more than 200 mRNAs differentially expressed in Grsf1cKO muscle at this age. Notably, mRNAs encoding proteins involved in mitochondrial function, inflammatory reaction, and ion transport, including Mgarp, Cxcl10, Nfkb2, and Sln, were significantly elevated in aged Grsf1cKO muscle. Our findings suggest that GRSF1 deficiency exacerbates the functional decline of aged skeletal muscle, likely through multiple downstream genes.
Project description:The ubiquitin-proteasome and autophagy-lysosome pathways are the two major routes for protein and organelle clearance. In skeletal muscle, both systems’ excessive activation induces severe muscle loss. Although altered proteasomal function has been observed in various myopathies, the specific role of proteasomal activity in skeletal muscle has not been determined by loss-of-function approaches. Here, we report that muscle-specific deletion of a crucial proteasomal gene, Rpt3, resulted in profound muscle atrophy and decrease in force. Rpt3 null muscles showed reduced proteasomal activity in early age, accumulation of basophilic structure, disorganization of sarcomere, and formation of vacuoles and concentric membranous structures in electronmicroscope. We also observed accumulation of ubiquitin, p62, LC3, TDP43, FUS and VCP proteins. Proteasomal activity is important to preserve muscle mass and to maintain myofiber integrity. Our results suggest that inhibition/alteration of proteasomal activity can contribute to myofiber degeneration and weakness in muscle disorders, such as inclusion body myositis, characterized by accumulation of abnormal inclusions. Tibialis anterior muscles from Rpt3 null and control mice. each 3 mice.