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The mutational spectrum of many genes and their contribution to the global prevalence of hereditary hearing loss is still widely unknown. In this study, we have performed the mutational screening of EYA4 gene by DHLPC and NGS in a large cohort of 531 unrelated Spanish probands and one Australian family with autosomal dominant non-syndromic hearing loss (ADNSHL). In total, 9 novel EYA4 variants have been identified, 3 in the EYA4 variable region (c.160G > T; p.Glu54*, c.781del; p.Thr261Argfs*34 and c.1078C > A; p.Pro360Thr) and 6 in the EYA-HR domain (c.1107G > T; p.Glu369Asp, c.1122G > T; p.Trp374Cys, c.1281G > A; p.Glu427Glu, c.1282-1G > A, c.1601C > G; p.S534* and an heterozygous copy number loss encompassing exons 15 to 17). The contribution of EYA4 mutations to ADNSHL in Spain is, therefore, very limited (~1.5%, 8/531). The pathophysiology of some of these novel variants has been explored. Transient expression of the c-myc-tagged EYA4 mutants in mammalian COS7 cells revealed absence of expression of the p.S534* mutant, consistent with a model of haploinsufficiency reported for all previously described EYA4 truncating mutations. However, normal expression pattern and translocation to the nucleus were observed for the p.Glu369Asp mutant in presence of SIX1. Complementary in silico analysis suggested that c.1107G > T (p.Glu369Asp), c.1281G > A (p.Glu427Glu) and c.1282-1G > A variants alter normal splicing. Minigene assays in NIH3T3 cells further confirmed that all 3 variants caused exon skipping resulting in frameshifts that lead to premature stop codons. Our study reports the first likely pathogenic synonymous variant linked to DFNA10 and provide further evidence for haploinsufficiency as the common underlying disease-causing mechanism for DFNA10-related hearing loss.

Branchio-oto-renal (BOR) and Stickler (STL) syndromes are disorders that include hearing loss among their clinical features. STL syndrome type I (STL1) is a combination of ophthalmic, orofacial, articular, and auditory manifestations, caused by mutations in the COL2A1. BOR syndrome is an autosomal dominant trait encompassing branchial, otic and renal anomalies because of mutations in EYA1, SIX1 and SIX5. In this study, we have clinically and genetically diagnosed a proband that displayed STL1 and BOR syndromes. This patient and his younger brother exhibited hearing loss and cleft palate. Both siblings and their mother also showed myopia, congenital non-progressive vitreous anomaly and a flat face. Taken together, these clinical features are consistent with the diagnosis of a familial case of STL. Sequence analysis revealed in the three patients a novel COL2A1 mutation (c.1468_1475delinsT) that accounted for a STL1 phenotype. The proband also displayed pre-auricular pits, branchial fistulae and renal agenesis that define BOR syndrome. Interestingly, this patient carries an EYA1 mutation, p.R328X, which was not present in the two other patients or in his healthy father, supporting that the mutation arose de novo. In conclusion, this report highlights the importance of molecular testing and detailed clinical evaluation for the diagnosis of syndromes with overlapping phenotypic features.

We report an infant with auditory neuropathy secondary to the Q829X mutation in the gene encoding otoferlin (OTOF). Included in a universal newborn hearing screening program, the subject passed the otoacoustic emission (OAEs) test. Given that the infant had a familial history of deafness auditory brainstem response (ABR) testing was performed, revealing a profound hearing impairment. The genetic study confirmed that the subject was homozygous for the Q829X mutation in OTOF. The patient underwent a cochlear implant, obtaining satisfactory results. The moderately high prevalence of this mutation in the Spanish population could produce a significant false negative rate in newborn hearing screening programs using OAEs.

Objective: To determine the features of hearing loss due to the Q829X mutation in the OTOF gene, the third most frequent mutation causing prelingual deafness reported so far in the Spanish population., Materials and Methods: We carried out genetic characterisation of 16 individuals from a consanguineous family from Cantabria, in which 4 members were affected by deafness., Results: All 4 hearing impaired individuals were homozygous for the Q829X mutation in the OTOF gene. The auditory defect was a profound, bilateral, symmetrical, sensorineural hearing loss of prelingual onset. No other clinical alterations were observed. Individuals heterozygous for the Q829X mutation were unaffected., Conclusions: The Q829X mutation in the OTOF gene causes severe to profound sensorineural hearing loss of prelingual onset. Early detection of individuals carrying this mutation is important for the application of palliative treatment and special education.