Steven J. H. Bom

Mutations in the WFS1 gene that cause low-frequency sensorineural hearing loss are small non-inactivating mutations

Abstract. Hereditary hearing impairment is an extremely heterogeneous trait, with more than 70 identified loci. Only two of these loci are associated with an auditory phenotype that predominantly affects the low frequencies (DFNA1 and DFNA6/14). In this study, we have completed mutation screening of the WFS1 gene in eight autosomal dominant families and twelve sporadic cases in which affected persons have low-frequency sensorineural hearing impairment (LFSNHI). Mutations in this gene are known to be responsible for Wolfram syndrome or DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness), which is an autosomal recessive trait. We have identified seven missense mutations and a single amino acid deletion affecting conserved amino acids in six families and one sporadic case, indicating that mutations in WFS1 are a major cause of inherited but not sporadic low-frequency hearing impairment. Among the ten WFS1 mutations reported in LFSNHI, none is expected to lead to premature protein truncation, and nine cluster in the C-terminal protein domain. In contrast, 64% of the Wolfram syndrome mutations are inactivating. Our results indicate that only non-inactivating mutations in WFS1 are responsible for non-syndromic low-frequency hearing impairment.

Progressive cochleovestibular impairment caused by a point mutation in the COCH gene at DFNA9.

Objectives: Analysis of phenotype‐genotype correlation.

Vestibular deterioration precedes hearing deterioration in the P51S COCH mutation (DFNA9): an analysis in 74 mutation carriers.

Objectives: To analyze cochleovestibular impairment features in P51S COCH mutation carriers (n = 22) in a new, large Dutch family and to compare the results to those obtained in previously identified similar mutation carriers (n = 52). To evaluate age-related features between progressive hearing and vestibular impairment of all mutation carriers (n = 74). Study Design: Family study. Methods: Regression analysis was performed in relation to age to outline the development of hearing thresholds, speech recognition scores, and vestibulo-ocular reflex time constant as the key vestibular response parameter. Results: Pure tone thresholds, phoneme recognition scores, and vestibular responses of the mutation carriers in the new family were essentially similar to those previously established in all other mutation carriers. Hearing started to deteriorate in all mutation carriers from 43 years of age onwards, whereas deterioration of vestibular function started from age 34. Conclusion: Vestibular impairment starts earlier, progresses more rapidly, and, eventually, is more complete than hearing impairment in P51S COCH mutation carriers.

Autosomal dominant low-frequency hearing impairment (DFNA6/14): a clinical and genetic family study.

Objective To delineate the phenotype and genotype of an autosomal dominant low-frequency sensorineural nonsyndromic hearing impairment trait in relation to similar traits. Study Design Family study, including retrospective case reviews. Setting Tertiary referral center. Patients Hearing impairment was documented in 11 family members in five generations, 8 of whom were alive and participated in this study. Intervention Diagnostic. Main Outcome Measures Clinical study: medical and otologic history and examination, retrieval of previous audiograms, pure-tone audiometry, and statistical analysis of audiometric data. Genetic study: linkage analysis of blood samples in 18 clinically affected and nonaffected family members. Results Hearing impairment had been present since early childhood, mainly affecting the low frequencies (mean threshold 45 dB HL at 0.25–1 kHz); speech recognition was hardly affected during the first three decades of life. Higher frequencies became involved with increasing age, thus causing a flat-type audiogram at middle age and down-sloping audiograms after age 60 years. Progression was mild but significant at all frequencies (0.5 dB/year at 0.25 kHz to 1.3 dB/year at 8 kHz) and persisted after correction was applied for normal presbyacusis. The trait was linked to chromosome 4p16.3, in a region comprising both the previously located, closely adjacent DFNA6 and the DFNA14 loci for low-frequency hearing impairment. Conclusion A third family (designated Dutch II) was identified with a low-frequency hearing impairment trait showing linkage to chromosome 4p16.3 (DFNA6/14). The progression of hearing impairment beyond presbyacusis in the current study is unprecedented for DFNA6/14 traits.