Audiological Evaluation of Affected Members from a Dutch DFNA8/12 (TECTA) Family

In DFNA8/12, an autosomal dominantly inherited type of nonsyndromic hearing impairment, the TECTA gene mutation causes a defect in the structure of the tectorial membrane in the inner ear. Because DFNA8/12 affects the tectorial membrane, patients with DFNA8/12 may show specific audiometric characteristics. In this study, five selected members of a Dutch DFNA8/12 family with a TECTA sensorineural hearing impairment were evaluated with pure-tone audiometry, loudness scaling, speech perception in quiet and noise, difference limen for frequency, acoustic reflexes, otoacoustic emissions, and gap detection. Four out of five subjects showed an elevation of pure-tone thresholds, acoustic reflex thresholds, and loudness discomfort levels. Loudness growth curves are parallel to those found in normal-hearing individuals. Suprathreshold measures such as difference limen for frequency modulated pure tones, gap detection, and particularly speech perception in noise are within the normal range. Distortion otoacoustic emissions are present at the higher stimulus level. These results are similar to those previously obtained from a Dutch DFNA13 family with midfrequency sensorineural hearing impairment. It seems that a defect in the tectorial membrane results primarily in an attenuation of sound, whereas suprathreshold measures, such as otoacoustic emissions and speech perception in noise, are preserved rather well. The main effect of the defects is a shift in the operation point of the outer hair cells with near intact functioning at high levels. As most test results reflect those found in middle-ear conductive loss in both families, the sensorineural hearing impairment may be characterized as a cochlear conductive hearing impairment

Mutations in the human a-tectorin gene cause autosomal dominant non- syndromic hearing impairment.

The tectorial membrane is an extracellular matrix of the inner ear that contacts the stereocilia bundles of specialized sensory hair cells. Sound induces movement of these hair cells relative to the tectorial membrane, deflects the stereocilia, and leads to fluctuations in hair-cell membrane potential, transducing sound into electrical signals. a-tectorin is one of the major non-collagenous components of the tectorial membrane. Recently, the gene encoding mouse a-tectorin (Tecta) was mapped to a region of mouse chromosome 9, which shows evolutionary conservation with human chromosome 11q (ref. 3), where linkage was found in two families, one Belgian (DFNA12; ref. 4) and the other, Austrian (DFNA8; unpublished data), with autosomal dominant non-syndromic hearing impairment. We determined the complete sequence and the intron-exon structure of the human TECTA gene. In both families, mutation analysis revealed missense mutations which replace conserved amino-acid residues within the zona pellucida domain of TECTA. These findings indicate that mutations in TECTA are responsible for hearing impairment in these families, and implicate a new type of protein in the pathogenesis of hearing impairment

A Novel TECTA Mutation in a Dutch DFNA8/12 Family Confirms Genotype–Phenotype Correlation

A novel TECTA mutation, p.R1890C, was found in a Dutch family with nonsyndromic autosomal dominant sensorineural hearing impairment. In early life, presumably congenital, hearing impairment occurred in the midfrequency range, amounting to about 40 dB at 1 kHz. Speech recognition was good with all phoneme recognition scores exceeding 90%. An intact horizontal vestibuloocular reflex was found in four tested patients. The missense mutation is located in the zona pellucida (ZP) domain of α-tectorin. Mutations affecting the ZP domain of α-tectorin are significantly associated with midfrequency hearing impairment. Substitutions affecting other amino acid residues than cysteines show a significant association with hearing impairment without progression. Indeed, in the present family progression seemed to be absent. In addition, the presently identified mutation affecting the ZP domain resulted in a substantially lesser degree of hearing impairment than was previously reported for DFNA8/12 traits with mutations affecting the ZP domain of α-tectorin

Mid-frequency DFNA8/12 hearing loss caused by a synonymous TECTA mutation that affects an exonic splice enhancer.

Contains fulltext : 69348.pdf (publisher's version ) (Closed access)Autosomal dominant hearing loss is highly heterogeneous. Hearing impairment mainly involves the mid-frequencies (500-2000 Hz) in only a low percentage of the cases. In a Dutch family with autosomal dominant mid-frequency/flat hearing loss, genome-wide SNP analysis combined with fine mapping using microsatellite markers mapped the defect to the DFNA8/12 locus, with a maximum two-point LOD score of 3.52. All exons and intron-exon boundaries of the TECTA gene, of which mutations are causative for DFNA8/12, were sequenced. Only one heterozygous synonymous change in exon 16 (c.5331G>A; p.L1777L) was found to segregate with the hearing loss. This change was predicted to cause the loss of an exonic splice enhancer (ESE). RT-PCR using primers flanking exon 16 revealed, besides the expected PCR product from the wild-type allele, a smaller fragment only in the affected individual, representing part of an aberrant TECTA transcript lacking exon 16. The aberrant splicing is predicted to result in a deletion of 37 amino acids (p.S1758Y/G1759_N1795del) in alpha-tectorin. Subsequently, the same mutation was detected in two out of 36 individuals with a comparable phenotype. Owing to the position of the protein deletion just N-terminal of the zona pellucida (ZP) domain of alpha-tectorin, it is likely that the deletion of 37 amino acids may affect the proteolytic processing, structure and/or function of this domain, which results in a clinical phenotype comparable to that of missense mutations in the ZP domain. In addition, this is the first report of a synonymous mutation that affects an ESE and causes hereditary hearing loss