AUTHOR=Girotto Giorgia , Morgan Anna , Krishnamoorthy Navaneethakrishnan , Cocca Massimiliano , Brumat Marco , Bassani Sissy , La Bianca Martina , Di Stazio Mariateresa , Gasparini Paolo 

TITLE=Next Generation Sequencing and Animal Models Reveal SLC9A3R1 as a New Gene Involved in Human Age-Related Hearing Loss

JOURNAL=Frontiers in Genetics

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2019.00142

DOI=10.3389/fgene.2019.00142

ISSN=1664-8021

ABSTRACT=<p>Age-related hearing loss (ARHL) is the most common sensory impairment in the elderly affecting millions of people worldwide. To shed light on the genetics of ARHL, a large cohort of 464 Italian patients has been deeply characterized at clinical and molecular level. In particular, 46 candidate genes, selected on the basis of genome-wide association studies (GWAS), animal models and literature updates, were analyzed by targeted re-sequencing. After filtering and prioritization steps, <italic>SLC9A3R1</italic> has been identified as a strong candidate and then validated by “<italic>in vitro”</italic> and <italic>“in vivo”</italic> studies. Briefly, a rare (MAF: 2.886e-5) missense variant c.539G &gt; A, p.(R180Q) was detected in two unrelated male patients affected by ARHL characterized by a severe to profound high-frequency hearing loss. The variant, predicted as damaging, was not present in healthy matched controls. Protein modeling confirmed the pathogenic effect of p.(R180Q) variant on protein’s structure leading to a change in the total number of hydrogen bonds. <italic>In situ</italic> hybridization showed <italic>slc9a3r1</italic> expression in zebrafish inner ear. A zebrafish knock-in model, generated by CRISPR-Cas9 technology, revealed a reduced auditory response at all frequencies in <italic>slc9a3r1</italic><sup>R180Q/R180Q</sup> mutants compared to <italic>slc9a3r1</italic><sup>+/+</sup> and <italic>slc9a3r1</italic><sup>+/R180Q</sup> animals. Moreover, a significant reduction (5.8%) in the total volume of the saccular otolith (which is responsible for sound detection) was observed in <italic>slc9a3r1</italic><sup>R180Q/R180Q</sup> compared to <italic>slc9a3r1</italic><sup>+/+</sup> (<italic>P</italic> = 0.0014), while the utricular otolith, necessary for balance, was not affected in agreement with the human phenotype. Overall, these data strongly support the role of <italic>SLC9A3R1</italic> gene in the pathogenesis of ARHL opening new perspectives in terms of diagnosis, prevention and treatment.</p>