Genetic and Epigenetic Investigations on Pulmonary Hypertension Syndrome in Meat Type- Chickens

This dissertation presents a collection of studies that investigate the genetic and epigenetic associations to ascites phenotype in broiler chickens. Ascites is a significant metabolic disease associated with fast-growing meat-type chickens (broilers) and is a terminal result of pulmonary hypertension syndrome PHS. It is a multi-factorial syndrome caused by interactions between genetic, physiological, environmental, and managemental factors. It was estimated that ascites accounts for losses of about US$1 billion annually worldwide and for over 25% of broilers mortality. Although traditional and molecular genetic methods in the selection and in performance improvements, has greatly reduced ascites frequency, yet it has not eliminated its occurrence. Therefore, this dissertation aimed to 1) develop SNP assays for the gene region of HTR2B to examine the possible association with ascites phenotype and measure gene and allele specific expression in different tissues at different developmental age stages under hypoxic conditions, 2) investigate the association of mitochondrial prevalence in multiple tissues with ascites susceptibility and resistance in broilers, and genes known to regulate mitochondrial biogenesis were assessed, and 3) mapping genome-wide changes in chromatin accessibility for pulmonary artery tissue in ascites - susceptible and ascites- resistant lines under normal and hypoxic conditions using ATAC-seq technology (Assay for Transposase accessible Chromatin with high-throughput sequencing). Altogether, this collection of studies provides new insights into the genetic and epigenetic basis of the ascites syndrome in chicken