DIFFERENTIAL GENE EXPRESSION IN LUNG TISSUE OF WOODEN BREAST SYNDROME AFFECTED AND UNAFFECTED COMMERCIAL BROILER CHICKENS
Date
2018-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
For years, the commercial boiler chicken industry has focused its breeding
efforts on producing feed-efficient broiler chickens that produce large amounts of
meat in a short amount of time to accommodate the high consumer demand for poultry
products. The economic welfare of the poultry industry is dependent upon the quality
of the meat produced; therefore, the rise in muscle disorders and myopathies that
jeopardize meat quality are concerning to growers. This study focuses on the novel
muscle disease, Wooden Breast Syndrome, which is characterized by an abnormally
hard pectoralis major muscle. Many studies have also identified muscle hypoxia and
oxidative stress as significant symptoms of Wooden Breast Syndrome indicative of
respiratory system impairments. In particular, this study will characterize gene
expression differences in the lung tissues of affected and unaffected commercial
broiler chickens using functional analysis tools to determine which specific pathways
or cellular functions are affected by this disease. The purpose of this research is to
gain a better understanding of the disease etiology of Wooden Breast Syndrome, to
understand how it affects the health of commercial broiler chickens, to gain insight
into ways to remedy hypoxia and oxidative stress in affected birds, and to understand
the lung’s contribution to this disease.
Starting in March 2017, a large live animal experiment on Wooden Breast
Syndrome was conducted in which approximately 2,100 broilers were raised to market
age. After being euthanized by cervical dislocation, birds were examined for Wooden
Breast Syndrome, necropsies were performed, and tissue samples were taken from the
breast muscle, liver, and lung. For this study, a total of 12 samples were used,
including 6 affected (3 females and 3 males) and 6 unaffected (3 females and 3 males).
Differentially expressed genes in the lung tissues between unaffected and affected
birds were identified by RNA analysis and functional analysis was completed using
IPA® Functional Analysis Software.
A total of 141 differentially expressed genes were identified using Cuffdiff
v2.2.1. The top upregulated (heat shock proteins, SPP1, FABP4, etc.) and
downregulated (ALB, HSD17B2, SELENOP1, etc.) differentially expressed genes
were selected based on the most positive and negative Log2 fold change, respectively.
Functional analysis of the differentially expressed genes using IPA® identified 5 top
canonical pathways, several upstream regulators, and diseases or functions that were
significantly activated or inhibited in the affected birds. The results suggest Wooden
Breast Syndrome affects lipid metabolism and hypoxia and oxidative stress in the lung
tissue.
Analysis of the DE genes identified in lung tissue from broilers affected with
Wooden Breast Syndrome suggest the lungs do not have a significant role in the
development of Wooden Breast Syndrome. There is not enough evidence to support
that markers of immune response, hypoxia, and oxidative stress found in affected lung
tissues are activated by issues originating from the lung, as these responses can also be
attributed to the systemic impact of Wooden Breast Syndrome. A well-supported
finding from this research is the altered lipid metabolism in affected lung tissue, which
has been consistently observed in various tissues in broilers affected with Wooden
Breast Syndrome. These are only preliminary findings; therefore, the lungs’
involvement in Wooden Breast Syndrome cannot be entirely dismissed, as additional
studies must be completed to explore significant genes and pathways identified by this
research.
Description
Keywords
Biological Sciences, Wooden Breast Syndrome, gene expression in lung tissue