A Novel EYA1 Splicing Mutation in a Chinese Family With Branchio-Oto Syndrome: A Functional Analysis and Reproductive Intervention.

Abstract

Objectives: Branchio-oto syndrome (BOS) is an autosomal dominant disorder characterized by multiple system anomalies, typically sparing the kidneys. BOS exhibits considerable clinical heterogeneity and ethnic variability; most studies have been conducted in European populations rather than in Asian populations, and its prevalence is approximately 1 in 40,000. EYA1 is the most commonly implicated gene in BOS, with mutations ranging from missense to frameshift, splicing, and nonsense variants. Although splicing mutations are important contributors to the disease, previous research has paid less attention to novel mutations that cause aberrant RNA splicing and their pathogenic mechanisms. Furthermore, reproductive interventions aimed at preventing disease transmission have not been reported.

Methods: We collected samples from a three-generation Chinese family affected by BOS. Whole exome sequencing was used to screen for candidate causative genes. A minigene assay was performed to identify aberrant splicing products, and additional molecular biology techniques were employed to analyze the pathogenicity of the resulting mistranslated proteins. Preimplantation genetic testing (PGT), based on single-nucleotide polymorphism analysis, was utilized to prevent hearing loss in this family.

Results: Whole-exome sequencing identified a novel mutation, EYA1:c.1598-2AG>TA, which was classified as pathogenic according to American College of Medical Genetics and Genomics criteria. The minigene assay verified aberrant RNA splicing that is predicted to result in premature termination of EYA1 protein translation. Cytological experiments demonstrated that the truncated EYA1 protein is unstable, exhibits impaired nuclear translocation, and fails to interact properly with SIX1. PGT enabled the proband to give birth to a healthy boy.

Conclusion: We identified a novel splicing variant in the EYA1 gene and elucidated its potential molecular pathogenic mechanism through several functional experiments. Based on these findings, we successfully implemented PGT to ensure the birth of a healthy offspring free from BOS.