<i>Myh14</i> deficiency under ISO results in LVM hypertrophy, LVIDd dilation, increased cardiomyocyte size, fibrosis, intercalated disc disarray, and hypertrophic signals.

<p>Female mice of wild-type (WT), heterozygous (HET) and knockout (KO) <i>Myh14</i> genotypes were treated with ISO at 10–12 weeks of age (n = 6, 9, and 7, respectively). <i>Myh14</i> deficiency conferred an increase in ISO-induced LVM hypertrophy (A) and LVID dilation (B). There was a trend towards decreased ISO-induced EF (C) due to <i>Myh14</i> deficiency. Cardiomyocyte cross-sectional area, as measured by wheat germ agglutinin (WGA) staining (D), showed that cardiomyocytes from ISO-treated KO mice were more significantly hypertrophied compared to HET and WT mice (E). Dark gray bars (baseline in A and B; average of baseline and week 1 in C; control in E). Light gray bars (average of weeks 1–3 measures in A and B; average of weeks 2–3 measures in C; ISO-treated in E). <i>Myh14</i> deficiency conferred an increase in ISO-induced fibrosis (blue arrow) by Masson’s trichrome staining (F) and an increase in intercalated disc disarray (blue arrow) by β-catenin staining (G). Cardiac tissue gene expression of hypertrophic and fibrosis markers were examined by RT-PCR at the end of a 3-week ISO infusion (H). <i>Myc</i>, <i>Nppb</i>, and <i>Lgals3</i> were increased with <i>Myh14</i> deficiency. Error bars are SEM, n = 3. * represents t-test p-value < 0.05. ** represents t-test p-value < 0.005.</p

Significant association loci.

<p>Significant association loci.</p

Population distribution of echocardiographic measures at each time point.

<p>The violin plot is a combination of a boxplot and a kernel density plot (a smooth histogram) rotated on its side. The white dot represents the median. The black box represents the interquartile range (IQR). The black vertical line represents the whiskers spanning the lowest and the highest data within 1.5 IQR from the lower and upper quartile. A) The population distribution at each ISO treatment time point. B) The distribution of the changes in echocardiographic measures from baseline. C) The changes in echocardiographic measures compared to baseline at each ISO time point for individual classical inbred strains.</p

Variation in echocardiographic measures of cardiac structure and function among HMDP mouse strains.

<p>Black bars represent measurements under the baseline condition in ranked order. White bars represent measurements after 3 weeks of continuous ISO infusion. IVSd = interventricular septal wall thickness; LVIDd = left ventricular diastolic diameter; LVM = left ventricular mass; FS = fractional shortening. Error bars represent the standard errors of the means.</p

Experimental design.

<p>We characterized 104 classical and recombinant inbred mouse strains of the Hybrid Mouse Diversity Panel (HMDP) by serial echocardiograms at baseline, week 1, week 2, and week 3 under the control condition or chronic isoproterenol (ISO) infusion. The ✪ symbol indicates the time points echocardiograms were performed.</p

Genome-wide association for week 3 LVM.

<p>A. Manhattan plot for week 3 LVM. B. Regional plot for week 3 LVM around peak SNP rs27794497 (purple). C. Regional plot for week 3 LVM hypertrophy around SNP rs40560913 (purple). Pairwise r2 between the peak SNP and the surrounding SNPs are denoted by color scale.</p

Relationships between variation and correlated traits.

<p>There are three possible causal relationships when there is correlation among a SNP (single nucleotide polymorphism) S, a transcript (RNA) R, and a physiological or pathologic trait (phenotype) P. In the causal model, the SNP variation affects its transcript levels leading to the resulting phenotype. In the reactive model, the SNP acts on the phenotypes, which in turn affects transcript. In the independent model, the SNP variation acts on both the phenotype and transcript independently.</p

Principal component analysis of isoproterenol-induced changes from baseline.

<p>A. The variables factor map demonstrates the first three principal components that account for 74.8% of inter-strain variations. The first principal component corresponds roughly to LVIDd dilation and FS decrease. The second principal component corresponds to IVSd and LVM hypertrophy. The third principal component corresponds to early IVSd hypertrophy. The individual factor map projects the inbred mouse strains onto the first three principal components. Black dots highlight the classical (B) and recombinant (C) inbred strains and gray dots represent the remaining HMDP strains.</p

Regional plots of LV hypertrophy at chromosome 7 across time points.

<p>A. Regional plot for LVM at baseline. B. Regional plots for ISO-induced LVM hypertrophy at week 1. C. Regional plots for ISO-induced LVM hypertrophy at week 2. D. Regional plot for ISO-induced LV weight hypertrophy at week 3.</p

Correlations among echocardiographic traits across time points.

<p>A) Correlations among baseline body weight- and heart rate-adjusted traits across time points. B) Correlations among isoproterenol-induced changes in traits from baseline across time points. Colored dots represent the pairwise correlation r values with p-values exceeding Bonferroni corrected α significance level of 0.05. LV represents LV weight. Suffixes represent weekly echocardiographic time points under ISO treatment (0 = baseline, 1 = week 1, 2 = week 2, 3 = week 3) or control versus ISO LV weight at week 3 (c = control, i = ISO).</p