Cardiomyocyte-specific Rac1 conditional knockin (Rac1cKI) mice expressing a Rac1C178S mutant protein exhibited normal cardiac structure and function but developed more severe cardiac hypertrophy in response to angiotensin II (AngII) infusion, cardiomyocyte-specific overexpression of AngII type 1 receptor (AT1R), and cardiac pressure overload. The gene discussed is AGTR1; the disease is cardiac hypertrophy.