2011 |
Davie, Judith Kimberly |
R15Activity Code Description: Supports small-scale research projects at educational institutions that provide baccalaureate or advanced degrees for a significant number of the Nation’s research scientists but that have not been major recipients of NIH support. The goals of the program are to (1) support meritorious research, (2) expose students to research, and (3) strengthen the research environment of the institution. Awards provide limited Direct Costs, plus applicable F&A costs, for periods not to exceed 36 months. This activity code uses multi-year funding authority; however, OER approval is NOT needed prior to an IC using this activity code. |
Understanding the Role of the Class Ii Activator, Ciita, in Skeletal Muscle @ Southern Illinois University Carbondale
DESCRIPTION (provided by applicant): Skeletal muscle has a remarkable ability to grow and repair throughout life. Deficiencies in skeletal muscle regeneration contribute to normal human aging and muscular dystrophies. Understanding both the process of how muscle senses damage and the molecular details of how muscle is repaired are of central importance in human biology. We believe that we have identified a novel connection between the inflammatory response and skeletal muscle remodeling mediated by the myogenic regulatory family (MRF). The inflammatory response plays an important role in initiating skeletal muscle regeneration. One of the cytokines involved in the inflammation response is the anti-fibrotic agent interferon gamma (IFN-?). IFN-? has complex effects on myogenesis, but is required for efficient muscle regeneration in vivo. We have identified the class II transactivator, CIITA, as a factor that interacts with myogenin, the MRF that mediates terminal differentiation. In immune cells, IFN-? stimulates both the activation and repression of a large set of genes through the action of CIITA, which serves as both a co-activator and co-repressor. CIITA is activated by IFN-? through the JAK/STAT pathway which leads to the direct activation of CIITA by STAT1. CIITA has both constitutive and IFN-? stimulated roles in the cell. We have confirmed that CIITA is expressed in the C2C12 myoblast line and shown that CIITA acts as a specific inhibitor of myogenin's activity as a transcriptional activator of muscle specific genes. CIITA expression is stimulated by IFN-?, and both stimulation with IFN-? and over expression of CIITA down regulate muscle specific gene expression and inhibit differentiation. Thus, we hypothesize that CIITA is the mediator of the IFN-? signal in skeletal muscle cells. In this proposal, we seek to understand how CIITA contributes to myogenesis and muscle repair. First, we propose to extend our current work on the role of CIITA in myoblasts by confirming our preliminary findings in primary myoblasts and confirming the anti-differentiation effect of CIITA with over expression and knock down studies. We also plan to initiate studies on the role of IFN-? in normal myogenesis by characterizing the level of IFN-? produced by myoblasts and by blocking the IFN-? receptor to assay the effects of loss of IFN-? signaling. Next, we seek to understand the contribution of CIITA to muscle repair by conducting muscle damage studies on mice with a disruption of the CIITA allele. Finally, we seek to determine if CIITA is the mediator of IFN-? and STAT1 signaling in myoblasts. Our preliminary data suggests that CIITA and its inhibition of myogenin are responsible for many of the effects of IFN-? and STAT1 on myogenic cells. We will attempt to support our hypothesis by confirming that STAT1 activates CIITA in myoblasts and by using STAT1 inhibitors to confirm a loss of anti differentiation effects following IFN-? stimulation. We will then attempt to rescue this effect by over expressing CIITA. We will also assay for IFN-? effects in Myog-/- myoblasts to determine if myogenin is required to mediate the IFN-? mediated down regulation of muscle specific targets. PUBLIC HEALTH RELEVANCE: Skeletal muscle is able to grow and repair throughout life. When muscle cannot be repaired due to age or muscular dystrophies, this leads to a loss of the ability to move and eventually leads to death. This proposal seeks to characterize a novel link between the signaling induced by the inflammatory response to muscle damage and the factors that can repair muscle fibers. We have discovered a factor in skeletal muscle cells that both responds to the signals released from inflammation and represses the activity of a specific factor required for the final steps in rebuilding muscle. We propose that this system gives muscle the time it needs to initiate repair before committing to the final steps of repair. This proposal seeks to further characterize this factor in muscle cells and determine its cellular role in skeletal muscle differentiation and repair. This work has important implications in understanding how skeletal muscle repairs itself after injury and may be able to offer novel insight into how to stimulate muscle regeneration in the case of aging or disease.
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2015 |
Davie, Judith Kimberly |
R15Activity Code Description: Supports small-scale research projects at educational institutions that provide baccalaureate or advanced degrees for a significant number of the Nation’s research scientists but that have not been major recipients of NIH support. The goals of the program are to (1) support meritorious research, (2) expose students to research, and (3) strengthen the research environment of the institution. Awards provide limited Direct Costs, plus applicable F&A costs, for periods not to exceed 36 months. This activity code uses multi-year funding authority; however, OER approval is NOT needed prior to an IC using this activity code. |
Understanding the Role of Ifn-Gamma and Ciita in Skeletal Muscle @ Southern Illinois University Carbondale
? DESCRIPTION (provided by applicant): The objective of this study is to identify how the inflammatory cytokine, interferon gamma (IFN-?, which is up regulated in response to muscle injury resulting from trauma or disease, modulates muscle function and repair. The repair of skeletal muscle is essential to human health and inefficient repair leads to a loss of locomotion and eventually, to death. The inflammatory response plays an important role in responding to injury and initiating skeletal muscle repair. IFN-? plays both positive and negative roles in myogenesis and is required for efficient muscle regeneration in vivo. We have discovered that IFN-? acts through the class II transactivator, CIITA, by repressing the expression or activity o myogenin, the Myogenic Regulatory Factor (MRF) required for myofiber formation. In our studies to understand the mechanism of CIITA repression, we have discovered that IFN-?, through CIITA, acts to maintain the expression of the polycomb complex, PRC2, which is normally silenced during differentiation. CIITA recruits the PRC2 complex to repressed gene promoters and PRC2 represses gene expression by catalyzing the methylation of histone H3, lysine 27 (H3K27me3). We propose that transient expression of IFN-?, through CIITA, modulates myogenesis and promotes muscle repair, but suggest that deregulation of this signaling contributes to muscle disease by altering the gene expression profile in myofibers subject to IFN-? stimulation. In this proposal, we will determine how IFN-? and CIITA repress myogenin by determining if recruitment of activating factors such as MyoD are blocked in the presence of IFN-?, defining the epigenetic modifications used in the repression and determining whether the PRC2 complex is required for repression. Next, we will determine if genes known to be altered in H3K27me3 patterns upon differentiation are methylated in response to IFN-? and dependent on myogenin. These data will be correlated with the recruitment of EZH2 and the repression of gene expression. Lastly, we will confirm our findings in vivo and determine if chronic IFN-? can inhibit muscle repair. This work will utilize a new mouse model engineered to express low chronic levels of IFN-?. Using this mouse model, we will characterize the expression of CIITA and the PRC2 complex, determine if IFN-? target genes are deregulated, and characterize repair in the presence of chronic IFN-?. To understand the impact of IFN-? as part of the inflammatory infiltrate, the methylation profile and gene expression of IFN-? regulated gene targets will be assayed in mdx mice, which are known to have enhanced IFN-? expression as part of a chronic inflammation response. The proposed work will strengthen our understanding of the molecular events that occur during inflammation in skeletal muscle. This information will not only help elucidate the normal process of repair and regeneration, but also extend our knowledge about the potential deleterious effects of chronic inflammation, enhancing the understanding of diseases such as muscular dystrophy, cachexia and inflammatory myopathies and allowing the development of innovative therapies for these diseases.
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