Project description:To gain new insights into molecular changes in skeletal muscle aging and disease with a special focus on differential alternative splicing and senescence, we performed RNA-seq on rat gastrocnemius muscles of animals aged 6, 12, 18, 21, 24 and 27 months, using a rat sarcopenia model we had previously established.
Project description:Molecular mechanisms underlying sarcopenia, the age-related loss of skeletal muscle mass and function, remain unclear. To identify molecular changes that correlated best with sarcopenia and might contribute to its pathogenesis, we determined global gene expression profiles in muscles of rats aged 6, 12, 18, 21, 24, and 27 months. These rats exhibit sarcopenia beginning at 21 months. Correlation of the gene expression versus muscle mass or age changes, and functional annotation analysis identified gene signatures of sarcopenia distinct from gene signatures of aging. Specifically, mitochondrial energy metabolism (e.g., tricarboxylic acid cycle and oxidative phosphorylation) pathway genes were the most downregulated and most significantly correlated with sarcopenia. Also, perturbed were genes/pathways associated with neuromuscular junction patency (providing molecular evidence of sarcopenia-related functional denervation and neuromuscular junction remodeling), protein degradation, and inflammation. Proteomic analysis of samples at 6, 18, and 27 months confirmed the depletion of mitochondrial energy metabolism proteins and neuromuscular junction proteins. Together, these findings suggest that therapeutic approaches that simultaneously stimulate mitochondrogenesis and reduce muscle proteolysis and inflammation have potential for treating sarcopenia.
Project description:The fast and constant activity of the extraocular muscles (EOMs) impose mechanical and metabolic stresses not typically seen in limb skeletal muscles. These functional properties may explain why EOMs seem to age at a faster rate than other skeletal muscles. Using high-density cDNA microarrays, this study investigated the gene expression profile of EOMs and extensor digitorum longus muscles (EDL) of Fischer 344/Brown Norway F1 hybrid rats at 6-, 18- and 30-months of age. At 6-mo, 705 genes and expressed sequence tags (ESTs) were differentially expressed in EOMs (436 up, 269 down). Overall, the EOM profile at this age was mostly consistent with the increased expression of fetal, developmental and EOM-specific myosin isoforms, enzymes involved in glycolysis and TCA cycle, and ion transporters and pumps, confirming the notion that EOM may represent a distinct muscle group (PNAS 98:12062, 2001). Interestingly, at 18-mo only 36 probes were significantly different in EOM (15 up, 21 down), most of them ESTs. However, at 30-mo EOMs had 655 differentially expressed genes and ESTs (480 up, 175 down). In this age group, the EOM expression profile reverted to a pattern similar to that found at 6-mo, with evidence of ongoing tissue remodeling and increased expression of antioxidant enzymes. These results indicate that the gene expression profile of EOM and EDL evolve differently throughout the lifespan. Keywords: aging, muscle type comparison
Project description:The fast and constant activity of the extraocular muscles (EOMs) impose mechanical and metabolic stresses not typically seen in limb skeletal muscles. These functional properties may explain why EOMs seem to age at a faster rate than other skeletal muscles. Using high-density cDNA microarrays, this study investigated the gene expression profile of EOMs and extensor digitorum longus muscles (EDL) of Fischer 344/Brown Norway F1 hybrid rats at 6-, 18- and 30-months of age. At 6-mo, 705 genes and expressed sequence tags (ESTs) were differentially expressed in EOMs (436 up, 269 down). Overall, the EOM profile at this age was mostly consistent with the increased expression of fetal, developmental and EOM-specific myosin isoforms, enzymes involved in glycolysis and TCA cycle, and ion transporters and pumps, confirming the notion that EOM may represent a distinct muscle group (PNAS 98:12062, 2001). Interestingly, at 18-mo only 36 probes were significantly different in EOM (15 up, 21 down), most of them ESTs. However, at 30-mo EOMs had 655 differentially expressed genes and ESTs (480 up, 175 down). In this age group, the EOM expression profile reverted to a pattern similar to that found at 6-mo, with evidence of ongoing tissue remodeling and increased expression of antioxidant enzymes. These results indicate that the gene expression profile of EOM and EDL evolve differently throughout the lifespan. Experiment Overall Design: Total RNA was obtained with TRIzol (Invitrogen Carlsbad, CA) following the manufacturers recommended protocol. Tissues from 4 animals were combined into each RNA sample to decrease inter-subject variability. Biotinylated cRNA samples were hybridized to Affymetrix Rat Genome U34 gene chips (n=24 chips) described previously [McMullen et al. 2004]. Microarrays were washed and stained with a streptavidin-bound marker and scanned. Data were analyzed with Affymetrix Microarray Suite 5.0 software. Only genes with consistent absent/present calls in all four independent replicates per group were considered for further analysis. Comparisons the one-sided Wilcoxonâs signed rank test to estimate âincrease/no change/ decreaseâ difference calls for each pair-wise comparison. Only difference calls consistent in all pair-wise comparisons and with average changes > 2.00 were considered significant, resulting in a conservative list of genes with changed expression levels. Functional classification of genes was based on an extensive literature review.
Project description:In order to evaluate the gene expression profile of retinal microglia cells in different age, we purified CD11b-positive microglia from the retinas of wild type C57BL/6 mice at 3, 12, 18, and 24 months age using cell sorting method with flow cytometry. Age-related genes from isolated retinal microglia were performed using 16 Affymetrix GeneChips of Mouse Exon 1.0ST Arrays. Gene expression level between consecutive age groups (i.e. between 3 and 12 months, 12 and 18 months, and 18 and 24 months) was examined to identify microglia relevant aging genes that demonstrated significant changes. We identified a total 719 genes that showed increasing or decreasing more than 1.5-fold change (p<0.05, one-way ANOVA) for at least one of the three inter age-group comparisons. These identified genes were subjected to a hierarchical cluster analysis to visualize trends in differential expression across individual biological repeats in the 4 age groups.
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. Weight-matched cohorts of 22-month-old male C57BL/6 mice were provided ad libitum access to standard chow (control) or standard chow supplemented with 0.27% ursolic acid (UA) or 0.05% tomatidine (TM) for 2 months. After the 2 month treatment period, quadriceps femoris muscles were harvested. mRNA levels in muscles harvested from ursolic acid or tomatidine fed mice were normalized to levels in muscles fed control diet.