Functional Consequence of IRF6 Variants in Van der Woude Syndrome

Van der Woude syndrome (VWS) is the most common syndromic form of orofacial clefts (OFCs). The heritability of VWS is largely (~70%) explained by variants in the IRF6 gene. Experimental studies to confirm genetic variant effects are essential but are time intensive and expensive. Advancing next-generation sequencing techniques has made it possible to identify genetic variation quicker than their causal effects in disease processes can be ascertained. Therefore, employing computational tools to reliably predict their causal effects is crucial for advancing translational research. We conducted Sanger sequencing of the IRF6 gene in 46 VWS cases across 34 families to identify likely causal missense variants. We then assessed structure-informed stability changes to the IRF6 protein when these variants were incorporated into the protein, using DDGun3D. We compared DDGun3D predictions to results from previous experimental studies. Among four variants previously shown to prevent functional rescue in zebrafish, only the variant IRF6(NM_006147.4):c.881T>C, shown to cause rupture of zebrafish embryo, exhibited a high free energy change (∆∆G_fold = 3.5 kcal/mol), indicating that substantial predicted thermodynamic destabilization does not capture all disruptive function of IRF6. Our study demonstrates the utility of a protein structure-based computational approach for functional variant interpretation, providing a complementary method for studying genetic variation. Integrating computational predictions with experimental data can enhance our understanding of genetic conditions. However, success depends on fully elucidating protein structures, which is an active area of research.