A novel heterozygous pathogenic variant in HEY2 led to a familial form of non-syndromic Tetralogy of Fallot.

Tetralogy of Fallot (TOF) aetiologies remain largely unknown. Although syndromes with genetic cause have been involved, non-syndromic TOF are not completely elucidated, with a genetic diagnosis in less than 20% of the cases. HEY2 is a basic helix-loop-helix (bHLH) repressive transcription factor implicated in cardiac development. In this study, we identify a novel heterozygous missense variant in HEY2 gene segregating within a family presenting with non-syndromic TOF with autosomal dominant transmission. The identified variation c.171 G > C p.(Glu57Asp) was tested through gene reporter assay, revealing a complete disruption of HEY2 repressive activity. These results suggest that HEY2 is a novel gene implicated in the pathogenesis of Tetralogy of Fallot, expanding the genetic spectrum of this congenital heart defect and reinforcing the role of monogenic contributions in non-syndromic TOF.