Identification of a Novel EVC2 Variant in a Family with Non-Syndromic Tooth Agenesis and Its Potential Functional Implications.

Background/Objectives: Non-syndromic tooth agenesis (NSTA) is a congenital condition that causes the absence of one or more teeth without accompanying systemic abnormalities, which significantly affects quality of life. Genetic factors, including mutations in several specific genes, contribute to the pathogenesis of NSTA. This study investigates a novel EVC2 mutation in a patient with NSTA and explores its potential pathogenic mechanism, with the aim of enriching the spectrum of pathogenic genes. Methods: Whole-exome sequencing (WES) was performed on peripheral blood samples from a patient diagnosed with NSTA. Bioinformatics analysis was utilized to identify the mutation and assess its potential impact on protein structure and function. Molecular dynamics simulations were conducted to analyze structural alterations in the EVC2 protein. The binding affinity between EVC2, EVC, and Smoothened (SMO) was to determine the effect of mutation on protein-protein interaction. Protein localization and expression were analyzed using immunofluorescence and Western blotting. Reverse transcription quantitative PCR (RT-qPCR) was employed to evaluate downstream signaling pathway alterations. Results: A novel EVC2 mutation (c.1657_1660delinsA, p.Glu553_leu554delinsMet) was identified in the proband, and the mutation was maternally inherited. Molecular dynamics simulations revealed that the mutation resulted in a decrease in α-helical content and significant conformational changes in the protein structure. This led to reduced binding affinity between EVC2 and its ligands EVC and SMO, destabilizing the structural integrity of the protein complex. Despite these structural changes, EVC2 protein localization and expression were unaffected. Furthermore, a downregulation of GLI1 and SHH expression was observed, indicating impaired Hedgehog (Hh) signaling. The downregulation of the Hh signaling pathway impairs the tooth development process and may lead to the occurrence of tooth agenesis. Conclusions: A novel EVC2 mutation was identified in a patient with NSTA. Based on molecular dynamics simulations, it is hypothesized that this EVC2 variant could contribute to the pathogenesis of NSTA by impairing the EVC2-EVC-SMO complex formation, which may lead to downregulation of downstream GLI1 and SHH. These findings provide new insights into the molecular mechanisms underlying EVC2-mediated NSTA, suggesting that disruption of Hh signaling may represent a critical pathogenic mechanism.