The ERBB2 c.1795C>T, p.Arg599Cys variant is associated with left ventricular outflow tract obstruction defects in humans

Non-syndromic congenital heart defects (CHDs) are occasionally familial and left ventricular outflow tract obstruction (LVOTO) defects are among the subtypes with the highest hereditability. The aim of this study was to evaluate the pathogenicity of a heterozygous ERBB2 variant c.1795C>T, p.Arg599Cys identified in three families with LVOTO defects. Variant detection was done with exome sequencing. Western blotting, digital PCR, mass spectrometry (MS), MS microscopy, and flow cytometry were used to study the function of the ERBB2 variant c.1795C>T. Cardiac structure and function were studied in zebrafish embryos expressing human ERBB2 wild type or c.1795C>T. Proband-derived human induced pluripotent stem cell cardiomyocytes (hiPS-CMs) and endothelial cells (hiPS-ECs) were used for transcriptomic analyses. While phosphorylation of the ERBB2 p.Arg599Cys receptor was not altered, the variant affected dramatically the binding partners of the protein, indicating mislocalization of the mutant ERBB2 from plasma membrane to endoplasmic reticulum. Expression of human ERBB2 p.Arg599Cys in zebrafish embryos resulted in cardiomyocyte hypertrophy, increased cardiac wall thickness, and impaired fractional shortening. Transcriptomic analyses of hiPS-ECs and hiPS-CMs from an individual with the c.1795C>T variant showed aberrant expression of genes related to cardiovascular system development and abnormal response to oxidative stress in both cell types. In conclusion, the heterozygous variant ERBB2 c.1795C>T, p.Arg599Cys leads to abnormal cellular localization of the ERBB2 receptor and induces structural changes and dysfunction in the zebrafish embryo heart. This evidence expands previous findings from animal studies to humans and suggests variants in ERBB2 may be associated with CHD.