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Fig. 3 ERBB2 variant results in compromised heart function in zebrafish (A) Fractional shortening of the heart of the zebrafish embryos injected with the ERBB2 c.1795C>T plasmid (33 embryos), ERBB2 WT plasmid (29 embryos), empty vector (36 embryos), and no injection (41 embryos) indicate decreased pump function in the zebrafish embryos injected with the ERBB2 c.1795C>T plasmid. Median with interquartile range is presented. (B) Increased cardiac wall thickness as measured from brightfield videos (non-injected, n = 42 embryos; vector, n = 39 embryos; ERBB2 WT, n = 30 embryos; ERBB2 c.1795C>T, n = 33 embryos. (C) Increased myocardium thickness measured by phalloidin staining was seen in the zebrafish embryos injected with the ERBB2 c.1795C>T plasmid (uninjected, n = 18 embryos; vector, n = 22 embryos; ERBB2 WT, n = 22 embryos; ERBB2 c.1795C>T, n = 22 embryos). (D) No differences in the number of myocardial nuclei within the four experimental groups was seen (14 uninjected embryos, 22 empty vector embryos, 20 WT ERBB2 embryos, 19 c.1795C>T embryos). Myocardium was identified based on anatomical location and phalloidin staining. (E) Myocardial cell area measured by membrane localized mCherry-CAAX staining in each group indicated slightly enlarged cells in the zebrafish embryo injected with the ERBB2 WT (212 cardiomyocytes from 16 embryos), ERBB2 c.1795C>T plasmid (262 cardiomyocytes from 20 embryos) or only empty vector injected embryos (151 cardiomyocytes from 19 embryos). (F) Example images of phalloidin staining of the heart. The ventricle lumen is filled with red blood cells (zebrafish red blood cells are nucleated) and myocardium identified with phalloidin staining. Scale bar, 50 μm. Statistical tests have been done using the Kruskal-Wallis test, ∗∗∗∗p < 0.0001, ∗∗∗p < 0.001. (B)–(D) are presented as Tukey Box and Whiskers.