Candidate Gene Analysis for Ascites in Broilers

Our collaborative group at University of Arkansas has been investigating the underlying physiology, histopathology, and genetics of Idiopathic Pulmonary Arteriole Hypertension (IPAH) or ascites in chickens. Development of research lines for resistance or susceptibility has been the basis for the mapping of chromosomal regions associated with susceptibility or resistance to ascites.  Regions identified include two regions on chromosome 9, one on chromosome 27 and one on chromosome Z.  Within each of these regions we have identified candidate genes that are known to affect hypertension or vaso-constriction in humans or other mammals.  Re-sequencing of some of these candidate genes has identified single nucleotide (SNP) polymorphisms in coding sequence or transcription factor binding sites.  Association studies have demonstrated significant epistasis in that the association of these regions with ascites phenotype varies with experimental line or in commercial breeding lines.  Our findings suggest that the histopathology and genetics of ascites in chickens may be very similar to those underlying some forms of hypertension in humans.  Thus, our data contribute to development of the chicken as potential medical model for hypertension in humans, as well as identification of targets for selection to reduce ascites in broiler breeding programs.