Insights into the molecular basis of wooden breast based on comparative analysis of fast- and slow-growth broilers

Wooden breast has emerged as an important condition in the poultry industry and affects the breast muscle of commercial meat-type chickens (broilers). Thus far, the condition has been classified as a myopathy, confirmed to not have an infectious origin, with molecular data showing the muscle to be under oxidative stress. The objective in this study was to query the functional origins of wooden breast and reveal its molecular similarities to known conditions based on pathway analyses. To carry out an in-depth comparative analysis, we generated RNAseq data from wooden breast affected birds and incorporated breast specific transcriptomic data from previously published studies. The comparative datasets were constructed from a range of commercial fast-growth and slow-growth varieties. Analysis of high-impact variants identified from transcriptome data provided a list of genes important in cell signaling, cell proliferation, cytoskeletal development, and calcium metabolism as being affected by nucleotide changes. Overlaying the lists of significantly differentially expressed genes with the list of high-impact variants produced a list of twenty genes that suggest an association of mechanistic and functional causes for woody breast; supporting a polygenic basis for this condition. Our study demonstrates that wooden breast shows an age-dependent gene expression pattern, with pathway analysis showing enrichment of glycolysis, cell differentiation, tumor suppression and inhibition, further indicating a complex condition with few similarities to myopathies. In summary, our results indicate the existence of a mechanistic, heritable basis for wooden breast, the drivers of which deserve more in-depth investigation. Additionally, they also suggest wooden breast to be a more complex condition than previously reported, potentially involving other organ systems.