Gradual Symmetric Progression of DFNA34 Hearing Loss Caused by an NLRP3 Mutation and Cochlear Autoinflammation.

OBJECTIVE: To characterize the audiometric phenotype of autosomal-dominant DFNA34 hearing loss (HL) caused by a missense substitution in the NLRP3 gene. NLRP3 encodes a critical component of the NLRP3 inflammasome that is activated in innate immune responses. STUDY DESIGN: This study was conducted under protocol 01-DC-0229 approved by the NIH Combined Neurosciences IRB. We performed medical and developmental history interviews and physical and audiological examinations of affected individuals with DFNA34 HL caused by the p.Arg918Gln mutation of NLRP3. We retrospectively reviewed audiological reports, when available, from other health care centers. SETTING: Federal biomedical research facility. SUBJECTS: Eleven members of a North American family segregating p.Arg918Gln. MAIN OUTCOME MEASURES: Pure-tone thresholds, rates of pure-tone threshold progression, and speech discrimination scores. RESULTS: Eight subjects had bilateral sensorineural HL with an onset in the late 2nd to 4th decade of life. Slowly progressive HL initially primarily affected high frequencies. Low and middle frequencies were affected with advancing age, resulting in moderate HL with a downsloping audiometric configuration. The average annual threshold deterioration was 0.9 to 1.5 dB/yr. Speech recognition scores ranging from 60 to 100% were consistent with cochlear, but not retrocochlear, etiology. Three subjects (16, 22, and 32 yr old) had normal hearing thresholds. CONCLUSION: DFNA34 HL has an onset during early adulthood and progresses approximately 1.2 dB/yr.

A common SLC26A4-linked haplotype underlying non-syndromic hearing loss with enlargement of the vestibular aqueduct.

BACKGROUND: Enlargement of the vestibular aqueduct (EVA) is the most common radiological abnormality in children with sensorineural hearing loss. Mutations in coding regions and splice sites of the SLC26A4 gene are often detected in Caucasians with EVA. Approximately one-fourth of patients with EVA have two mutant alleles (M2), one-fourth have one mutant allele (M1) and one-half have no mutant alleles (M0). The M2 genotype is correlated with a more severe phenotype. METHODS: We performed genotype-haplotype analysis and massively parallel sequencing of the SLC26A4 region in patients with M1 EVA and their families. RESULTS: We identified a shared novel haplotype, termed CEVA (Caucasian EVA), composed of 12 uncommon variants upstream of SLC26A4. The presence of the CEVA haplotype on seven of ten 'mutation-negative' chromosomes in a National Institutes of Health M1 EVA discovery cohort and six of six mutation-negative chromosomes in a Danish M1 EVA replication cohort is higher than the observed prevalence of 28 of 1006 Caucasian control chromosomes (p<0.0001 for each EVA cohort). The corresponding heterozygous carrier rate is 28/503 (5.6%). The prevalence of CEVA (11 of 126) is also increased among M0 EVA chromosomes (p=0.0042). CONCLUSIONS: The CEVA haplotype causally contributes to most cases of Caucasian M1 EVA and, possibly, some cases of M0 EVA. The CEVA haplotype of SLC26A4 defines the most common allele associated with hereditary hearing loss in Caucasians. The diagnostic yield and prognostic utility of sequence analysis of SLC26A4 exons and splice sites will be markedly increased by addition of testing for the CEVA haplotype.

NLRP3 mutation and cochlear autoinflammation cause syndromic and nonsyndromic hearing loss DFNA34 responsive to anakinra therapy.

The NLRP3 inflammasome is an intracellular innate immune sensor that is expressed in immune cells, including monocytes and macrophages. Activation of the NLRP3 inflammasome leads to IL-1ß secretion. Gain-of-function mutations of NLRP3 result in abnormal activation of the NLRP3 inflammasome, and cause the autosomal dominant systemic autoinflammatory disease spectrum, termed cryopyrin-associated periodic syndromes (CAPS). Here, we show that a missense mutation, p.Arg918Gln (c.2753G > A), of NLRP3 causes autosomal-dominant sensorineural hearing loss in two unrelated families. In family LMG446, hearing loss is accompanied by autoinflammatory signs and symptoms without serologic evidence of inflammation as part of an atypical CAPS phenotype and was reversed or improved by IL-1ß blockade therapy. In family LMG113, hearing loss segregates without any other target-organ manifestations of CAPS. This observation led us to explore the possibility that resident macrophage/monocyte-like cells in the cochlea can mediate local autoinflammation via activation of the NLRP3 inflammasome. The NLRP3 inflammasome can indeed be activated in resident macrophage/monocyte-like cells in the mouse cochlea, resulting in secretion of IL-1ß. This pathway could underlie treatable sensorineural hearing loss in DFNA34, CAPS, and possibly in a wide variety of hearing-loss disorders, such as sudden sensorineural hearing loss and Meniere's disease that are elicited by pathogens and processes that stimulate innate immune responses within the cochlea.

Hearing loss associated with enlarged vestibular aqueduct and zero or one mutant allele of SLC26A4.

OBJECTIVES/HYPOTHESIS: To characterize the severity and natural history of hearing loss, and the prevalence of having a cochlear implant in a maturing cohort of individuals with enlarged vestibular aqueduct (EVA) and zero or one mutant allele of SLC26A4. STUDY DESIGN: Prospective cohort study of subjects ascertained between 1998 and 2015 at the National Institutes of Health Clinical Center. METHODS: Study subjects were 127 individuals (median age, 8 years; range, 0-59 years) with EVA in at least one ear. RESULTS: Ears with EVA and zero or one mutant allele of SLC26A4 had mean 0.5/1/2/4-kHz pure-tone averages of 62.6 and 52.9 dB HL, respectively, in contrast to EVA ears with two mutant alleles of SLC26A4 (88.1 dB HL; P < .01). This association was independent of age, sex, or side of EVA (P < .001). Natural history of hearing loss was not associated with number of mutant alleles (P = .94). The prevalence of having a cochlear implant was nine (12%) of 76, two (13%) of 15, and 12 (38%) of 32 subjects with zero, one, and two mutant alleles, respectively (P = .00833). This association was not independent (P = .534) but reflected underlying correlations with age at time of first audiogram (P = .003) or severity of hearing loss (P = .000). CONCLUSIONS: Ears with EVA and zero or one mutant allele of SLC26A4 have less severe hearing loss, no difference in prevalence of fluctuation, and a lower prevalence of cochlear implantation in comparison to ears with two mutant alleles of SLC26A4. LEVEL OF EVIDENCE: NA Laryngoscope, 127:E238-E243, 2017.

Atypical patterns of segregation of familial enlargement of the vestibular aqueduct.

OBJECTIVES/HYPOTHESIS: Hearing loss and enlarged vestibular aqueduct (EVA) can be inherited as an autosomal recessive trait caused by mutant alleles of the SLC26A4 gene. In some other families, EVA does not segregate in a typical autosomal recessive pattern. The goal of this study was to characterize the SLC26A4 genotypes and phenotypes of extended families with atypical segregation of EVA. STUDY DESIGN: Prospective study of cohort of families ascertained between 1998 and 2014 at the National Institutes of Health Clinical Center. METHODS: Study subjects were members of eight families segregating EVA in at least two members who were not related as siblings. Evaluations included pure-tone audiometry, temporal bone imaging, SLC26A4 nucleotide sequence analysis, SLC26A4-linked marker genotype and haplotype analysis, and pedigree analysis. RESULTS: One family had members with EVA caused by different etiologies, and two families had pseudodominant inheritance of recessive mutations of SLC26A4. In five families, the etiology remained unknown and could include inheritance of mutant alleles at another genetic locus, nongenetic influences, or a combination of these factors. CONCLUSIONS: Familial EVA can demonstrate a variety of atypical segregation patterns. Pseudodominant inheritance of SLC26A4 mutations or recessive alleles of other hearing loss genes may be more likely to occur in families in which deaf individuals have intermarried. The etiologic basis of atypical segregation of EVA without detectable SLC26A4 mutations remains unknown. Future studies of these families may reveal novel genes for EVA. LEVEL OF EVIDENCE: NA Laryngoscope, 126:E240-E247, 2016.

Vestibular Dysfunction in Patients with Enlarged Vestibular Aqueduct.

OBJECTIVE: Enlarged vestibular aqueduct (EVA) is the most common inner ear malformation. While a strong correlative relationship between EVA and hearing loss is well established, its association with vestibular dysfunction is less well understood. In this study, we examine the effects of EVA on the vestibular system in patients with EVA. STUDY DESIGN: Prospective, cross-sectional study of a cohort ascertained between 1999 and 2013. SETTING: National Institutes of Health Clinical Center, a federal biomedical research facility. SUBJECTS AND METHODS: In total, 106 patients with unilateral or bilateral EVA, defined as a midpoint diameter greater than 1.5 mm, were referred or self-referred to participate in a study of the clinical and molecular aspects of EVA. Clinical history was ascertained with respect to the presence or absence of various vestibular signs and symptoms and history of head trauma. Videonystagmography (VNG), cervical vestibular evoked myogenic potential (cVEMP), and rotational vestibular testing (RVT) were performed to assess the vestibular function. RESULTS: Of the patients with EVA, 45% had vestibular signs and symptoms, and 44% of tested patients had abnormal VNG test results. An increased number of vestibular signs and symptoms was correlated with the presence of bilateral EVA (P = .008) and a history of head injury (P < .001). Abnormal VNG results also correlated with a history of head injury (P = .018). CONCLUSION: Vestibular dysfunction is common in patients with EVA. However, not all patients with vestibular signs and symptoms have abnormal vestibular test results. Clinicians should be aware of the high prevalence of vestibular dysfunction in patients with EVA.

Cone responses in Usher syndrome types 1 and 2 by microvolt electroretinography.

PURPOSE: Progressive decline of psychophysical cone-mediated measures has been reported in type 1 (USH1) and type 2 (USH2) Usher syndrome. Conventional cone electroretinogram (ERG) responses in USH demonstrate poor signal-to-noise ratio. We evaluated cone signals in USH1 and USH2 by recording microvolt level cycle-by-cycle (CxC) ERG. METHODS: Responses of molecularly genotyped USH1 (n = 18) and USH2 (n = 24) subjects (age range, 15-69 years) were compared with those of controls (n = 12). A subset of USH1 (n = 9) and USH2 (n = 9) subjects was examined two to four times over 2 to 8 years. Photopic CxC ERG and conventional 30-Hz flicker ERG were recorded on the same visits. RESULTS: Usher syndrome subjects showed considerable cone flicker ERG amplitude losses and timing phase delays (P < 0.01) compared with controls. USH1 and USH2 had similar rates of progressive logarithmic ERG amplitude decline with disease duration (-0.012 log µV/y). Of interest, ERG phase delays did not progress over time. Two USH1C subjects retained normal response timing despite reduced amplitudes. The CxC ERG method provided reliable responses in all subjects, whereas conventional ERG was undetectable in 7 of 42 subjects. CONCLUSIONS: Cycle-by-cycle ERG showed progressive loss of amplitude in both USH1 and USH2 subjects, comparable to that reported with psychophysical measures. Usher subjects showed abnormal ERG response latency, but this changed less than amplitude with time. In USH syndrome, CxC ERG is more sensitive than conventional ERG and warrants consideration as an outcome measure in USH treatment trials.

Use of SLC26A4 mutation testing for unilateral enlargement of the vestibular aqueduct.

IMPORTANCE: Approximately one-half of all subjects with unilateral or bilateral hearing loss with enlargement of the vestibular aqueduct (EVA) will have SLC26A4 gene mutations. The number (0, 1, or 2) of mutant alleles of SLC26A4 detected in an individual subject with EVA is each associated with a distinct combination of diagnostic and prognostic information as well as probability of recurrence of EVA in siblings. OBJECTIVE: To evaluate the results of SLC26A4 mutation testing in subjects with unilateral EVA. (The study objective was formulated before data were collected.) DESIGN: Prospective cross-sectional study of cohort ascertained between 1998 and 2012. SETTING: National Institutes of Health Clinical Center, a federal biomedical research facility. PARTICIPANTS: Twenty-four subjects (10 males, 14 females) with unilateral EVA, defined as a midpoint diameter greater than 1.5 mm, who were referred or self-referred to participate in a study about the clinical and molecular analysis of EVA. Twenty-one (87.5%) of 24 subjects were white. Mean age was 10.3 years (age range, 5-39 years). INTERVENTION: SLC26A4 mutation analysis. MAIN OUTCOMES AND MEASURES: Audiometric results, the presence or absence of EVA, and the number of mutant alleles of SLC26A4. RESULTS: Approximately 8.3% of the subjects with unilateral EVA had 2 mutant SLC26A4 alleles, 16.7% had 1 mutant allele, and 75.0% had 0 mutant alleles. CONCLUSIONS AND RELEVANCE: Unilateral EVA can be associated with all possible SLC26A4 genotype results. The distinct combination of prognoses and recurrence probability associated with each genotype supports the clinical use of testing for SLC26A4 mutations in subjects with unilateral EVA.

Allelic hierarchy of CDH23 mutations causing non-syndromic deafness DFNB12 or Usher syndrome USH1D in compound heterozygotes.

BACKGROUND: Recessive mutant alleles of MYO7A, USH1C, CDH23, and PCDH15 cause non-syndromic deafness or type 1 Usher syndrome (USH1) characterised by deafness, vestibular areflexia, and vision loss due to retinitis pigmentosa. For CDH23, encoding cadherin 23, non-syndromic DFNB12 deafness is associated primarily with missense mutations hypothesised to have residual function. In contrast, homozygous nonsense, frame shift, splice site, and some missense mutations of CDH23, all of which are presumably functional null alleles, cause USH1D. The phenotype of a CDH23 compound heterozygote for a DFNB12 allele in trans configuration to an USH1D allele is not known and cannot be predicted from current understanding of cadherin 23 function in the retina and vestibular labyrinth. METHODS AND RESULTS: To address this issue, this study sought CDH23 compound heterozygotes by sequencing this gene in USH1 probands, and families segregating USH1D or DFNB12. Five non-syndromic deaf individuals were identified with normal retinal and vestibular phenotypes that segregate compound heterozygous mutations of CDH23, where one mutation is a known or predicted USH1 allele. CONCLUSIONS: One DFNB12 allele in trans configuration to an USH1D allele of CDH23 preserves vision and balance in deaf individuals, indicating that the DFNB12 allele is phenotypically dominant to an USH1D allele. This finding has implications for genetic counselling and the development of therapies for retinitis pigmentosa in Usher syndrome. ACCESSION NUMBERS: The cDNA and protein Genbank accession numbers for CDH23 and cadherin 23 used in this paper are AY010111.2 and AAG27034.2, respectively.