Your dog might have descended from mountain dogs!
Endothelial PAS domain-containing protein 1 (EPAS1) is a transcription factor, meaning it activates other genes. In response to low oxygen or hypoxia, EPAS1 will work to activate genes that help the body adapt to a low oxygen environment.
In some populations of humans, EPAS1 variants do appear to be associated with increased sprinting or power athletic abilities. In dogs, we see EPAS1 variants most commonly in dogs from mountainous regions, such as the Tibetan Mastiff.