IDENTIFICATION OF THE GENETIC MECHANISMS ASSOCIATED WITH MUSCLE MYOPATHIES IN POULTRY

The purpose of the proposed study is to explore the hypothesis that following damage, skeletal muscle satellite cells are failing to regenerate myoblasts and results in fibrotic scar tissue; overall, we believe that because stem cells are restricted to a limited number of divisions satellite cells are being exhausted and eventually resulting in Wooden Breast (WB) Muscle Myopathies. This is based on evidence that myogenic regulatory factors were down-regulated along with TGF-β and DNMT3 being identified as the top upstream regulators identified by genetic analysis. It is known that today's broiler that has been genetically selected for an increase in pectoralis major (PM) skeletal muscle, also has an increased the number of satellite cells. Skeletal muscle satellite cells can eventually become exhausted and fail to regenerate myoblasts. Several studies have hypothesized that this failure to regenerate could be due to continuous regeneration attempts.It is possible that the demand for PM skeletal muscle regeneration in broilers is resulting in the exhaustion of satellite cells.This proposed project will evaluate in vitro and in vivo methods to explore molecular genetic networks to obtain results that can be used on a global and cellular level, all of which have the potential to increase our understanding of WB and reveal the mechanism of this myopathy. Through analyzing WB cells in vitro, the environmental conditions can be controlled to determine their proliferation and viability through BCECF/AM, DAPI staining and qRT-PCR. The analyzation of myoblast differentiation into myotubes could represent a similar process which is occurring in birds with WB. By evaluating the telomere length and telomerase activity we gain another insight into the mitotic clock of the cells, to help determine if the satellite cells in broilers are being "overworked" and exhausted which then leads to the failure to repair damaged tissue. Although gene expression has been analyzed this does not always result in alterations in protein expression. Assessing the proteome allows for a comprehensive analysis of proteins, which may be associated with WB. Lastly, through ChIP qPCR histone modifications at H3K27me3 and H3K4me3 will be evaluated for changes in expression of myogenic regulatory factors and myoblast growth factors in an attempt to document changes in satellite cells associated with WB. This information will allow for an understanding of the molecular genetic mechanisms involved with woody breast which will facilitate future endeavors to alleviate the myopathy. In turn, leading to healthier birds, economic benefit, and consumer satisfaction.