Correlation between genotype and phenotype in patients with bi-allelic SLC26A4 mutations

Area of Science:

• Genetics
• Otolaryngology
• Molecular Biology

Background:

• SLC26A4 gene mutations are the primary cause of prelingual hearing loss in East Asia.
• Phenotypes associated with SLC26A4 mutations vary, including non-syndromic hearing loss and Pendred syndrome.

Purpose of the Study:

• To investigate the correlation between SLC26A4 genotype and inner ear phenotypes in patients with enlarged vestibular aqueduct (EVA).
• To elucidate the underlying molecular mechanisms linking genotype to hearing loss severity.

Main Methods:

• Analysis of 111 patients with bi-allelic SLC26A4 mutations and bilateral EVA.
• Genotyping to identify common mutations (p.H723R, c.919-2A>G, p.T410M).
• Quantitative PCR and cell-based assays to assess pendrin transcript levels, surface expression, and anion exchange activity.

Main Results:

• p.H723R, c.919-2A>G, and p.T410M were the most frequent mutations in Korean EVA patients.
• Patients with c.919-2A>G or p.T410M mutations exhibited better residual hearing than those with homozygous p.H723R mutations.
• Normal pendrin transcript levels were observed in patients with homozygous c.919-2A>G mutations, with higher surface expression and anion exchange activity for p.T410M compared to p.H723R.

Conclusions:

• A significant correlation exists between SLC26A4 genotype and the degree of residual hearing in East Asian populations.
• Genotype influences the functional expression of pendrin, impacting inner ear phenotypes.
• Understanding these genotype-phenotype correlations can aid in predicting hearing loss progression and potential therapeutic strategies.