Hepatic Gene Expression Analysis of Wooden Breast Disease in Chickens

Wooden Breast Disease (WBD) is a myopathy of fast growing commercial broiler chickens, the most obvious symptom being palpably hard breast muscle (pectoralis major) tissue. The affected breast muscle is both visually and texturally unappealing to consumers, causing economic loss to the poultry industry. Recent research on WBD has focused on understanding the molecular contributors of breast muscle damage, fibrosis, and lipidosis resulting from WBD. The current study was conducted to explore the differentially expressed (DE) genes in the liver of chickens affected by the Wooden Breast myopathy. Live birds, from a purebred line of commercial broiler chickens, were clinically examined by manual palpation of breast muscle at 47 days of age. Liver tissue samples from 4 affected and 4 unaffected birds were used in high throughput mRNA sequencing (RNA-seq) using Illumina HiSeq 2500 platform. After aligning sequence reads to the chicken reference genome (Galgal4) using TopHat, differential gene and transcript expression analysis was performed using Cuffdiff. The 113 significant differentially expressed genes were used for functional annotation clustering with DAVID Bioinformatics Resources. In affected birds, 71 of these genes were upregulated and 42 were downregulated. The most prominent differentially expressed gene pathways included transmembrane, extracellular matrix receptor interaction, and oxidoreductase. In conclusion, this study shows breast muscle is not the sole tissue affected by WBD, indicating further physiological complexities involved in the occurrence of this muscle abnormality in commercial chickens.