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The control of transcription is crucial for homeostasis in mammals. A previous selective sweep analysis of horse racing performance revealed a 19.6 kb candidate regulatory region 50 kb downstream of the Endothelin3 (EDN3) gene. Here, the region was narrowed to a 5.5 kb span of 14 SNVs, with elite and sub-elite haplotypes analyzed for association to racing performance, blood pressure and plasma levels of EDN3 in Coldblooded trotters and Standardbreds. Comparative analysis of human HiCap data identified the span as an enhancer cluster active in endothelial cells, interacting with genes relevant to blood pressure regulation. Coldblooded trotters with the sub-elite haplotype had significantly higher blood pressure compared to horses with the elite performing haplotype during exercise. Alleles within the elite haplotype were part of the standing variation in pre-domestication horses, and have risen in frequency during the era of breed development and selection. These results advance our understanding of the molecular genetics of athletic performance and vascular traits in both horses and humans. Author summary: A previous study discovered that a genomic region close to the Endothelin3 gene was associated with harness racing performance. Here, careful phenotypic documentation of athletic performance and blood pressure measurements in horses, followed by state-of-the-art genomics, allowed us to identify a 5.5 kb regulatory region located approximately 50 kb 3' of the EDN3 gene. A comparative analysis of the region using human HiCap data supported a regulatory role as, in endothelial cells, interaction was observed between the region and multiple genes relevant to blood pressure regulation and athletic performance. Long range cis-regulatory modules are critical for cooperatively controlling multiple genes located within transcriptionally active domains. We measured blood pressure in Coldblooded trotters during exercise and demonstrated that horses with two copies of the elite-performing haplotype had lower blood pressure during exercise and better racing performance results, compared to horses with two copies of the sub-elite performing haplotype. In addition, horses with the elite-performing haplotype also had higher levels of Endothelin3 in plasma. The results reported here are important for understanding the biological mechanisms behind blood pressure regulation in relation to racing performance in both horses and humans. [ABSTRACT FROM AUTHOR]

Objective: Shear forces play a key role in the maintenance of vessel wall integrity. Current understanding regarding sheardependent gene expression is mainly based on in vitro or in vivo observations with experimentally deranged shear, hence reflecting acute molecular events in relation to flow. Our objective was to combine computational fluid dynamic (CFD) simulations with global microarray analysis to study flow-dependent vessel wall biology in the aortic wall under physiological conditions. Methods and Results: Male Wistar rats were used. Animal-specific wall shear stress (WSS) magnitude and vector direction were estimated using CFD based on aortic geometry and flow information acquired by magnetic resonance imaging. Two distinct flow pattern regions were identified in the normal rat aortic arch; the distal part of the lesser curvature being exposed to low WSS and a non-uniform vector direction, and a region along the greater curvature being subjected to markedly higher levels of WSS and a uniform vector direction. Microarray analysis identified numerous novel mechanosensitive genes, including Trpc4 and Fgf12, and confirmed well-known ones, e.g. Klf2 and Nrf2. Gene ontology analysis revealed an over-representation of genes involved in transcriptional regulation. The most differentially expressed gene, Hand2, is a transcription factor previously shown to be involved in extracellular matrix remodeling. HAND2 protein was endothelial specific and showed higher expression in the regions exposed to low WSS with disturbed flow. Conclusions: Microarray analysis validated the CFD-defined WSS regions in the rat aortic arch, and identified numerous novel shear-sensitive genes. Defining the functional importance of these genes in relation to atherosusceptibility may provide important insight into the understanding of vascular pathology. [ABSTRACT FROM AUTHOR]