SPI1 and atrial fibrillation: The results from immunochemistry revealed significantly higher PU.1 expressions in Ad-PU.1 immunodeficient mice compared to the empty vector group both under normal saline or AF infection conditions, and PU.1 levels of Ad-PU.1 mice were even significantly higher in AF conditions than the normal saline treatment (**P < 0.01) (Fig. 6A, B).