Studies by Banach and colleagues (2014, 2018, 2023) on the role of Pak1 activity as a factor in SAN dysfunction and atrial fibrillation (AF) focused on the effect of loss of activity of Pak1 to result in an increase in the activity of NADPH oxidase 2 (NOX2) to generate reactive oxygen species (ROS). The gene discussed is CYBB; the disease is atrial fibrillation.