Date of Graduation

8-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Cell & Molecular Biology (PhD)

Degree Level

Graduate

Department

Cell & Molecular Biology

Advisor/Mentor

Rhoads, Douglas D.

Committee Member

McNabb, David S.

Second Committee Member

Henry, Ralph L.

Third Committee Member

Thallapuranam, Suresh

Keywords

Ascites; Broilers; Genetics; GWAS; Next-generation sequencing; Pulmonary hypertension

Abstract

These studies have investigated different candidate genomic regions for their contributions to ascites in broilers. Ascites syndrome is a manifestation of idiopathic pulmonary arteriole hypertension that concerns the poultry industry worldwide. Investigations have demonstrated the disease to be genetically regulated and to exhibit moderate to high heritabilities. Although previous studies have indicated a few chromosomes to be involved with ascites, no genes have been identified to date with direct links to the disease. This dissertation presents a collection of studies that determine the genomic and genetic interactions for regions on chromosome 2 and 9 for ascites phenotypes in broiler chickens. The dissertation further focuses on developing genetic markers for selection of broilers for ascites-resistance. To achieve these aims, the studies described here use two high throughput approaches- genome-wide association and whole genome re-sequencing. A previously identified region on chromosome 9 was further investigated with fine mapping using SNPs. A region on chromosome 2 was investigated using 2 different SNPs. Neither of these regions was found to contain more than a minor association with ascites. Re-evaluation of chromosome 2 and 9 by whole genome resequencing identified multiple regions. One of the most intriguing regions was further evaluated and found to contain the most significant association with ascites ever identified. The region contains the CPQ gene. The data support three different alleles for CPQ with two of those alleles associated with resistance to ascites. Those two alleles appear to be expressed at higher levels in three tissues critical for oxygen homeostasis. Taken together, this collection of studies provides an insight and adds to our current understanding of the molecular correlates of the disease. The markers developed in these studies will be useful in breeding schemes for ascites resistance in the broiler industry.

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