ERBB2 R599C variant is associated with left ventricular outflow tract obstruction defects in human

Background and aims Non-syndromic congenital heart defects (CHD) are occasionally familial and left ventricular out flow 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 R599C identified in three families with LVOTO defects. Methods 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 R599C. Cardiac structure and function were studied in zebrafish embryos expressing human ERBB2 WT or R599C. Patient-derived human induced pluripotent stem cell cardiomyocytes (hiPS-CM) and endothelial cells (hiPS-ECs) were used for transcriptomic analyses. Results While phosphorylation of the ERBB2 R599C receptor was not altered, the variant affected dramatically the binding partners of the protein and lead to mislocalization of ERBB2 from plasma membrane to ER and mitochondria. Expression of human ERBB2 R599C in zebrafish embryos resulted in cardiomyocyte hypertrophy, increased cardiac wall thickness, and impaired fractional shortening, demonstrating that the mutant receptor induces functional and structural defects during heart development. Transcriptomic analyses of hiPS-ECs and hiPS-CMs from a patient with the R599C variant indicated aberrant expression of genes related to cardiovascular system development and abnormal response to oxidative stress in both cell types. Conclusion The heterozygous variant ERBB2 R599C leads to abnormal cellular localization of the ERBB2 receptor inducing structural changes and dysfunction in the zebrafish embryo heart. This evidence suggests ERBB2 as a novel disease gene for CHD.