(A–D) Data were gathered from mice at the time of the first baseline echocardiogram taken from male and female BRAF^fl/fl/Cre^+/− littermates (males: 7–8 weeks; females: 9–10 weeks). (A) Body weights. (B) Heart rate, ejection fraction and fractional shortening, global longitudinal strain (GLS) and global circumferential strain (GCS) were measured from B-mode images of long-axis views using VevoStrain speckle-tracking software. (C,D) Stroke volume, cardiac output, end diastolic volume (EDV), end systolic volume (ESV) and end diastolic LV mass (EDLVM) were measured from B-mode images of long-axis views using VevoStrain speckle-tracking software. Diastolic (d) and systolic (s) left ventricle (LV) internal diameter (ID) and wall thickness (WT: anterior plus posterior walls) measurements were measured from M-mode images of short axis views using VevoLab software. (E) Confirmation of recombination using cDNA prepared from RNA extracted from the hearts of male (upper image) and female (lower image) littermates 11 d post-tamoxifen treatment. PCR amplification used forward primers in exon 9 with reverse primers in exon 13. Deletion of exon 12 in cardiomyocytes resulted in the appearance of a smaller product in heart (H) but not kidney (K) of mice treated with tamoxifen (Tx) in corn-oil (CO) but not CO alone. Representative images are shown. (F–H) Immunoblot analysis of RAF isoforms (F) or phosphorylated and total ERK1/2 (G,H) in relation to Gapdh in samples of female or male (as indicated) mouse hearts treated with CO or Tx 4 days before administration of phenylephrine (PE) in PBS or PBS alone for 7 d. Representative immunoblots are shown. Densitometric analysis of the blots in H are in the right panels. Individual data points are shown with the mean and range.