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Daniela Ragancokova, Elena Rocca, Anne M.M. Oonk, Herbert Schulz, Elvira Rohde, Jan Bednarsch, Ilse Feenstra, Ronald J.E. Pennings, Hagen Wende, and Alistair N. Garratt Original citation: J Clin Invest. 2014;124(3):1214-1227. [...]

The olfactory bulb (OB) receives odor information from the olfactory epithelium and relays this to the olfactory cortex. Using a mouse model, we found that development and maturation of OB interneurons depends on the zinc finger homeodomain factor teashirt zinc finger family member 1 (TSHZ1). In mice lacking TSHZ1, neuroblasts exhibited a normal tangential migration to the OB; however, upon arrival to the OB, the neuroblasts were distributed aberrantly within the radial dimension, and many immature neuroblasts failed to exit the rostral migratory stream. Conditional deletion of Tshz1 in mice resulted in OB hypoplasia and severe olfactory deficits. We therefore investigated olfaction in human subjects from families with congenital aural atresia that were heterozygous for TSHZ1 loss-of-function mutations. These individuals displayed hyposmia, which is characterized by impaired odor discrimination and reduced olfactory sensitivity. Microarray analysis, in situ hybridization, and ChIP revealed that TSHZ1 bound to and regulated expression of the gene encoding prokineticin receptor 2 (PROKR2), a G protein--coupled receptor essential for OB development. Mutations in PROKR2 lead to Kallmann syndrome, characterized by anosmia and hypogonadotrophic hypogonadism. Our data indicate that TSHZ1 is a key regulator of mammalian OB development and function and controls the expression of molecules involved in human Kallmann syndrome., Introduction The olfactory bulb (OB) relays odor information from sensory neurons of the olfactory epithelium to higher brain centers. Interneurons located within the granule cell and glomerular layers modulate the [...]

Objective: To analyse the benefit of cochlear implantation in young deaf children with Waardenburg syndrome (WS) compared to a reference group of young deaf children without additional disabilities.Method: A retrospective study was conducted on children with WS who underwent cochlear implantation at the age of 2 years or younger. The post-operative results for speech perception (phonetically balanced standard Dutch consonant-vocal-consonant word lists) and language comprehension (the Reynell Developmental Language Scales, RDLS), expressed as a language quotient (LQ), were compared between the WS group and the reference group by using multiple linear regression analysis.Results: A total of 14 children were diagnosed with WS, and 6 of them had additional disabilities. The WS children were implanted at a mean age of 1.6 years and the 48 children of the reference group at a mean age of 1.3 years. The WS children had a mean phoneme score of 80% and a mean LQ of 0.74 at 3 years post-implantation, and these results were comparable to those of the reference group. Only the factor additional disabilities had a significant negative influence on auditory perception and language comprehension.Conclusions: Children with WS performed similarly to the reference group in the present study, and these outcomes are in line with the previous literature. Although good counselling about additional disabilities concomitant to the syndrome is relevant, cochlear implantation is a good rehabilitation method for children with WS. [ABSTRACT FROM AUTHOR]

Objective: Mutations in the transient receptor potential vanilloid 4 gene (TRPV4) can induce a great diversity of neuropathies. Together with these neuropathies, hearing loss can occur. This study is focused on providing an audiometric phenotype description of a Dutch family with spinal muscular atrophy caused by a mutation in TRPV4. Methods: A neurological examination was repeated and pure tone and speech audiometry were performed. Results: A large variety in neurological symptoms as well as variation in audiometric characteristics was observed. The severity of hearing loss is mild to moderate and the audiogram configuration is highly variable. The hearing loss of these patients has a progressive nature in general. The frequencies that deteriorate significantly differ between family members. When compared to presbyacusis patients, speech recognition scores of patients with a TRPV4 mutation are not clearly different. Conclusion: The function of TRPV4 in the inner ear is still elusive but it is suggested that TRPV4 is required for maintenance of cochlear function in stress conditions, like acoustic injury. We can neither confirm nor reject this based on the results obtained in this family. Therefore, one might consider advising patients with a TRPV4 mutation to avoid exposure to environmental influences such as noise exposure. [ABSTRACT FROM AUTHOR]

Abstract: Background: Regional recurrence of glottic squamous cell carcinoma was evaluated in patients with a clinically N0 neck who underwent selective upper-node dissection (SUND) or selective upper-node inspection (SUNI; surgical visualization and palpation of jugular lymph nodes at levels II and III) during (salvage) laryngectomy. Methods: In 152 patients, 291 clinically N0 (139 bilateral and 13 contralateral) necks were evaluated for occult neck metastases by SUNI or SUND during (salvage) laryngectomy. Results: Occult neck metastases were identified with SUNI or SUND in 7% of the necks (21 of 291). In 4% (n = 11) of the remaining 270 necks, regional recurrence was detected during follow-up evaluation. Thus, in these 8 patients, SUNI or SUND seemed to have failed. Conclusions: SUND or SUNI of levels II and III during (salvage) laryngectomy identified the vast majority of patients who needed extensive neck treatment. In the N0 necks, these techniques led to less morbidity than elective neck dissection. [Copyright &y& Elsevier]

Summary: A patient with Pendred/enlarge vestibular aqueduct (EVA) syndrome with a 26-year audiometric follow-up is presented, showing childhood onset of sensorineural hearing loss, characterized by several episodes of well-documented sudden transient deterioration in sensorineural hearing loss and vertigo elicited by head trauma. This report is unique in its detailed follow-up of hearing loss around the time of head trauma events, providing new evidence to show a causative relation between head trauma and sudden hearing loss in EVA/Pendred syndrome. [Copyright &y& Elsevier]

Clinical and genetic characteristics are presented of 2 patients from a Dutch Usher syndrome type III family who have a new homozygous USH3 gene mutation: 149-152delCAGG + insTGTCCAAT. One individual (IV: 1) is profoundly hearing impaired and has normal vestibular function and retinitis punctata albescens (RPA). The other individual is also profoundly hearing impaired, but has well-developed speech, vestibular areflexia, and retinitis pigmentosa sine pigmento (RPSP). These findings suggest that Usher syndrome type III can be clinically misdiagnosed as either Usher type I or II; that Usher syndrome patients who are profoundly hearing impaired and have normal vestibular function should be tested for USH3 mutations; and that RPA and RPSP can occur as fundoscopic manifestations of pigmentary retinopathy in Usher syndrome. [ABSTRACT FROM AUTHOR]

This review focuses on the following progressive nonsyndromic autosomal dominant (DFNA) trait loci: DFNA1, DFNA2, DFNA4, DFNA5, DFNA6/14(/38), DFNA7, DFNA9, DFNA10, DFNA15, DFNA16, DFNA17, DFNA20/26 and DFNA21. It describes age-related pure tone thresholds and speech discrimination scores related to age and the level of hearing impairment. Vestibular findings, as far as previous described, are included as well. [ABSTRACT FROM AUTHOR]

The progressive nonsyndromic autosomal dominant (DFNA) traits considered here are those linked to the DFNA2, DFNA5, DFNA6/14(/38), DFNA9, DFNA10, DFNA15, DFNA20/26 and DFNA21 loci. This is a report on our use of the method of `Age Related Typical Audiograms' (ARTA). This method was developed especially to characterize progressive hearing impairment phenotypes. Pure tone threshold data are plotted in a familiar audiogram-like format covering, where possible, decade steps in age (decade audiograms). Such plots, if characteristic and specific enough, can be used as phenotype `fingerprints'. The threshold features array is an additional tool that can be used for statistical testing between fingerprints corresponding to different traits. The issue of genotype-phenotype correlation is dealt with in the case of some loci with multi-family presentation and sufficiently established genotypes. [ABSTRACT FROM AUTHOR]

Laryngoceles and saccular cysts, which are abnormal dilatations of the laryngeal saccule, are uncommon. The etiology is unknown but is probably related to both congenital and acquired factors. These structures are usually asymptomatic and are incidentally discovered through radiographic studies for unrelated symptoms. We describe two patients with upper airway obstruction, one caused by a giant laryngocele and the other by a large saccular cyst. In the former patient, acute tracheotomy had to be performed. The laryngocele and saccular cyst were removed surgically, which relieved patients’ symptoms of upper airway obstruction. [ABSTRACT FROM AUTHOR]

Usher syndrome type II (USH2) is characterised by moderate to severe high-frequency hearing impairment, progressive visual loss due to retinitis pigmentosa and intact vestibular responses. Three loci are known for USH2, however, only the gene for USH2a ( USH2A) has been identified. Mutation analysis of USH2A was performed in 70 Dutch USH2 families. Ten mutations in USH2A were detected, of which three are novel, c.949C>A, c.2242C>T (p.Gln748X) and c.4405C>T (p.Gln1468X). Including 9 previously published Dutch USH2a families, estimates of the prevalence of USH2a in the Dutch USH2 population were made. Mutations were identified in 62% of the families. In 28% both mutated alleles were identified, whereas in 34% the mutation in only one allele was found. It is estimated that about 28% of the Dutch USH2 families have a different causative gene. Analysis of deduced haplotypes suggests that c.1256G>T (p.Cys419Phe) is a Dutch ancestral mutation, occurring in 16% of the alleles. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Congenital aural atresia (CAA) can occur as an isolated congenital malformation or in the context of a number of monogenic and chromosomal syndromes. CAA is frequently seen in individuals with an 18q deletion, which is characterized by intellectual disability, reduced white-matter myelination, foot deformities, and distinctive facial features. Previous work has indicated that a critical region for CAA is located in 18q22.3. We studied four individuals (from two families) with CAA and other features suggestive of an 18q deletion, and we detected overlapping microdeletions in 18q22.3 in both families. The minimal region of deletion overlap (72.9–73.4 Mb) contained only one known gene, TSHZ1, which was recently shown to be important for murine middle-ear development. Sequence analysis of the coding exons in TSHZ1 in a cohort of 11 individuals with isolated, nonsyndromic bilateral CAA revealed two mutations, c.723G>A (p.Trp241X) and c.946_947delinsA (p.Pro316ThrfsX16), and both mutations predicted a loss of function. Together, these results demonstrate that hemizygosity of TSHZ1 leads to congenital aural atresia as a result of haploinsufficiency. [ABSTRACT FROM AUTHOR]

In a Dutch consanguineous family with recessively inherited nonsyndromic hearing impairment (HI), homozygosity mapping combined with whole-exome sequencing revealed a MPZL2 homozygous truncating variant, c.72del (p.Ile24Metfs ∗ 22). By screening a cohort of phenotype-matched subjects and a cohort of HI subjects in whom WES had been performed previously, we identified two additional families with biallelic truncating variants of MPZL2 . Affected individuals demonstrated symmetric, progressive, mild to moderate sensorineural HI. Onset of HI was in the first decade, and high-frequency hearing was more severely affected. There was no vestibular involvement. MPZL2 encodes myelin protein zero-like 2, an adhesion molecule that mediates epithelial cell-cell interactions in several (developing) tissues. Involvement of MPZL2 in hearing was confirmed by audiometric evaluation of Mpzl2 -mutant mice. These displayed early-onset progressive sensorineural HI that was more pronounced in the high frequencies. Histological analysis of adult mutant mice demonstrated an altered organization of outer hair cells and supporting cells and degeneration of the organ of Corti. In addition, we observed mild degeneration of spiral ganglion neurons, and this degeneration was most pronounced at the cochlear base. Although MPZL2 is known to function in cell adhesion in several tissues, no phenotypes other than HI were found to be associated with MPZL2 defects. This indicates that MPZL2 has a unique function in the inner ear. The present study suggests that deleterious variants of Mplz2/MPZL2 affect adhesion of the inner-ear epithelium and result in loss of structural integrity of the organ of Corti and progressive degeneration of hair cells, supporting cells, and spiral ganglion neurons. [ABSTRACT FROM AUTHOR]

DFNB28 is characterized by prelingual, severe to profound sensorineural hearing impairment (HI). It is associated with mutations in exon 6 and 7 of TRIOBP and has not been reported in the European population. Here, we describe two isolated cases of Dutch origin with congenital, moderate HI and compound heterozygous mutations in TRIOBP . Three of the mutations are novel, one nonsense mutation (c.5014G>T (p.Gly1672*)) and two frameshift mutations (c.2653del (p.Arg885Alafs*120) and c.3460_3461del (p.Leu1154Alafs*29)). The fourth mutation is the known c.3232dup (p.Arg1078Profs*6) mutation. Longitudinal audiometric analyses in one of the subjects revealed that HI was stable over a period of 15 years. Vestibular function was normal. Predicted effects of the mutations do not explain the relatively mild phenotype in the presented subjects, whereas location of the mutation might well contribute to the milder HI in one of the subjects. It is known that isoform classes TRIOBP-4 and TRIOBP-5 are important for stereocilia stability and rigidity. To our knowledge, p.Gly1672* is the first pathogenic variant identified in DFNB28 that does not affect isoform class TRIOBP-4. This suggests that a single TRIOBP copy to encode wildtype TRIOBP-4 is insufficient for normal hearing, and that at least one TRIOBP copy to encode TRIOBP-5 is indispensable for normal inner ear function. Furthermore, this study demonstrates that DFNB28 can be milder than reported so far and that mutations in TRIOBP are thus associated with a heterogeneous phenotype. [ABSTRACT FROM AUTHOR]

Objectives Usher syndrome is an inherited disorder that is characterized by hearing impairment (HI), retinitis pigmentosa, and in some cases vestibular dysfunction. Usher syndrome type IIa is caused by mutations in USH2A . HI in these patients is highly heterogeneous and the present study evaluates the effects of different types of USH2A mutations on the audiometric phenotype. Data from two large centres of expertise on Usher Syndrome in the Netherlands and Sweden were combined in order to create a large combined sample of patients to identify possible genotype-phenotype correlations. Design A retrospective study on HI in 110 patients (65 Dutch and 45 Swedish) genetically diagnosed with Usher syndrome type IIa. We used methods especially designed for characterizing and testing differences in audiological phenotype between patient subgroups. These methods included Age Related Typical Audiograms (ARTA) and a method to evaluate the difference in the degree of HI developed throughout life between subgroups. Results Cross-sectional linear regression analysis of last-visit audiograms for the best hearing ear demonstrated a gradual decline of hearing over decades. The congenital level of HI was in the range of 16–33 dB at 0.25–0.5 kHz, and in the range of 51–60 dB at 1–8 kHz. The annual threshold deterioration was in the range of 0.4–0.5 dB/year at 0.25–2 kHz and in the range of 0.7–0.8 dB/year at 4–8 kHz. Patients with two truncating mutations, including homozygotes for the common c.2299delG mutation, developed significantly more severe HI throughout life than patients with one truncating mutation combined with one nontruncating mutation, and patients with two nontruncating mutations. Conclusions The results have direct implications for patient counselling in terms of prognosis of hearing and may serve as baseline measures for future (genetic) therapeutic interventions. [ABSTRACT FROM AUTHOR]

Purpose USH2A mutations are an important cause of retinitis pigmentosa (RP) with or without congenital sensorineural hearing impairment. We studied genotype–phenotype correlations and compared visual prognosis in Usher syndrome type IIa and nonsyndromic RP. Design Clinic-based, longitudinal, multicenter study. Participants Consecutive patients with Usher syndrome type IIa (n = 152) and nonsyndromic RP (n = 73) resulting from USH2A mutations from ophthalmogenetic clinics in the Netherlands and Belgium. Methods Data on clinical characteristics, visual acuity, visual field measurements, retinal imaging, and electrophysiologic features were extracted from medical charts over a mean follow-up of 9 years. Cumulative lifetime risks of low vision and blindness were estimated using Kaplan-Meier survival analysis. Main Outcome Measures Low vision and blindness. Results Participant groups had similar distributions of gender (48% vs. 45% males in Usher syndrome type IIa vs. nonsydromic RP; P = 0.8), ethnicity (97% vs. 99% European; P = 0.3), and median follow-up time (6.5 years vs. 3 years; P = 0.3). Usher syndrome type IIa patients demonstrated symptoms at a younger age (median age, 15 years vs. 25 years; P < 0.001), were diagnosed earlier (median age, 26 years vs. 36.5 years; P < 0.001), and became visually impaired 13 years earlier (median age, 41 years vs. 54 years; P < 0.001) based on VF and 18 years earlier based on VA (median age, 54 years vs. 72 years; P < 0.001) than nonsyndromic RP patients. The presence of 2 truncating mutations in USH2A was associated mostly with the syndromic phenotype, whereas other combinations were present in both groups. We found novel variants in Usher syndrome type IIa (25%) and nonsyndromic RP (19%): 29 missense mutations, 10 indels, 14 nonsense mutations, 9 frameshift mutations, and 5 splice-site mutations. Conclusions Most patients with USH2A -associated RP have severe visual impairment by age 50. However, those with Usher syndrome type IIa have an earlier decline of visual function and a higher cumulative risk of visual impairment than those without nonsyndromic RP. Complete loss of function of the USH2A protein predisposes to Usher syndrome type IIa, but remnant protein function can lead to RP with or without hearing loss. [ABSTRACT FROM AUTHOR]

Linkage analysis combined with whole-exome sequencing in a large family with congenital and stable non-syndromic unilateral and asymmetric hearing loss (NS-UHL/AHL) revealed a heterozygous truncating mutation, c.286_303delinsT (p.Ser96Ter), in KITLG . This mutation co-segregated with NS-UHL/AHL as a dominant trait with reduced penetrance. By screening a panel of probands with NS-UHL/AHL, we found an additional mutation, c.200_202del (p.His67_Cys68delinsArg). In vitro studies revealed that the p.His67_Cys68delinsArg transmembrane isoform of KITLG is not detectable at the cell membrane, supporting pathogenicity. KITLG encodes a ligand for the KIT receptor. Also, KITLG-KIT signaling and MITF are suggested to mutually interact in melanocyte development. Because mutations in MITF are causative of Waardenburg syndrome type 2 (WS2), we screened KITLG in suspected WS2-affected probands. A heterozygous missense mutation, c.310C>G (p.Leu104Val), that segregated with WS2 was identified in a small family. In vitro studies revealed that the p.Leu104Val transmembrane isoform of KITLG is located at the cell membrane, as is wild-type KITLG. However, in culture media of transfected cells, the p.Leu104Val soluble isoform of KITLG was reduced, and no soluble p.His67_Cys68delinsArg and p.Ser96Ter KITLG could be detected. These data suggest that mutations in KITLG associated with NS-UHL/AHL have a loss-of-function effect. We speculate that the mechanism of the mutation underlying WS2 and leading to membrane incorporation and reduced secretion of KITLG occurs via a dominant-negative or gain-of-function effect. Our study unveils different phenotypes associated with KITLG , previously associated with pigmentation abnormalities, and will thereby improve the genetic counseling given to individuals with KITLG variants. [ABSTRACT FROM AUTHOR]

Already 40 genes have been identified for autosomal-recessive nonsyndromic hearing impairment (arNSHI); however, many more genes are still to be identified. In a Dutch family segregating arNSHI, homozygosity mapping revealed a 2.4 Mb homozygous region on chromosome 11 in p15.1-15.2, which partially overlapped with the previously described DFNB18 locus. However, no putative pathogenic variants were found in USH1C, the gene mutated in DFNB18 hearing impairment. The homozygous region contained 12 additional annotated genes including OTOG, the gene encoding otogelin, a component of the tectorial membrane. It is thought that otogelin contributes to the stability and strength of this membrane through interaction or stabilization of its constituent fibers. The murine orthologous gene was already known to cause hearing loss when defective. Analysis of OTOG in the Dutch family revealed a homozygous 1 bp deletion, c.5508delC, which leads to a shift in the reading frame and a premature stop codon, p.Ala1838ProfsX31. Further screening of 60 unrelated probands from Spanish arNSHI families detected compound heterozygous OTOG mutations in one family, c.6347C>T (p.Pro2116Leu) and c. 6559C>T (p.Arg2187X). The missense mutation p.Pro2116Leu affects a highly conserved residue in the fourth von Willebrand factor type D domain of otogelin. The subjects with OTOG mutations have a moderate hearing impairment, which can be associated with vestibular dysfunction. The flat to shallow “U” or slightly downsloping shaped audiograms closely resembled audiograms of individuals with recessive mutations in the gene encoding α-tectorin, another component of the tectorial membrane. This distinctive phenotype may represent a clue to orientate the molecular diagnosis. [Copyright &y& Elsevier]

In a Dutch family with an X-linked postlingual progressive hearing impairment, a critical linkage interval was determined to span a region of 12.9 Mb flanked by the markers DXS7108 and DXS7110. This interval overlaps with the previously described DFNX4 locus and contains 75 annotated genes. Subsequent next-generation sequencing (NGS) detected one variant within the linkage interval, a nonsense mutation in SMPX. SMPX encodes the small muscle protein, X-linked (SMPX). Further screening was performed on 26 index patients from small families for which X-linked inheritance of nonsyndromic hearing impairment (NSHI) was not excluded. We detected a frameshift mutation in SMPX in one of the patients. Segregation analysis of both mutations in the families in whom they were found revealed that the mutations cosegregated with hearing impairment. Although we show that SMPX is expressed in many different organs, including the human inner ear, no obvious symptoms other than hearing impairment were observed in the patients. SMPX had previously been demonstrated to be specifically expressed in striated muscle and, therefore, seemed an unlikely candidate gene for hearing impairment. We hypothesize that SMPX functions in inner ear development and/or maintenance in the IGF-1 pathway, the integrin pathway through Rac1, or both. [ABSTRACT FROM AUTHOR]

In mammals, sound is detected by mechanosensory hair cells that are activated in response to vibrations at frequency-dependent positions along the cochlear duct. We demonstrate that inner ear supporting cells provide a structural framework for transmitting sound energy through the cochlear partition. Humans and mice with mutations in GAS2 , encoding a cytoskeletal regulatory protein, exhibit hearing loss due to disorganization and destabilization of microtubule bundles in pillar and Deiters' cells, two types of inner ear supporting cells with unique cytoskeletal specializations. Failure to maintain microtubule bundle integrity reduced supporting cell stiffness, which in turn altered cochlear micromechanics in Gas2 mutants. Vibratory responses to sound were measured in cochleae from live mice, revealing defects in the propagation and amplification of the traveling wave in Gas2 mutants. We propose that the microtubule bundling activity of GAS2 imparts supporting cells with mechanical properties for transmitting sound energy through the cochlea. [Display omitted] • GAS2 mutations cause hearing loss in mice and humans • GAS2 maintains microtubule bundle integrity in cochlear supporting cells • Supporting cell defects in Gas2 mutants compromise cochlear mechanics Chen et al. describe how mutations in GAS2 , encoding a microtubule-associated protein, cause hearing loss in mice and humans. They show that microtubule bundle integrity is compromised in cochlear supporting cells from Gas2 mutants, causing defects in the amplification and propagation of sound waves in the cochlea. [ABSTRACT FROM AUTHOR]