FoxO1 null mice (at e9.5) have underdeveloped blood vessels, whereas overexpression of the FoxO1 gene (at e10.5) results in reduced heart size, myocardium thickening (myocardium thickening also results from transgene expression of FoxO1 at e18.5), and eventual heart failure. This evidence concerns the gene FOXO1 and heart failure.