[Show abstract][Hide abstract] ABSTRACT: Optic atrophy (OA) and sensorineural hearing loss (SNHL) are key abnormalities in several syndromes, including the recessively inherited Wolfram syndrome, caused by mutations in WFS1. In contrast, the association of autosomal dominant OA and SNHL without other phenotypic abnormalities is rare, and almost exclusively attributed to mutations in the Optic Atrophy-1 gene (OPA1), most commonly the p.R445H mutation. We present eight probands and their families from the US, Sweden, and UK with OA and SNHL, whom we analyzed for mutations in OPA1 and WFS1. Among these families, we found three heterozygous missense mutations in WFS1 segregating with OA and SNHL: p.A684V (six families), and two novel mutations, p.G780S and p.D797Y, all involving evolutionarily conserved amino acids and absent from 298 control chromosomes. Importantly, none of these families harbored the OPA1 p.R445H mutation. No mitochondrial DNA deletions were detected in muscle from one p.A684V patient analyzed. Finally, wolframin p.A684V mutant ectopically expressed in HEK cells showed reduced protein levels compared to wild-type wolframin, strongly indicating that the mutation is disease-causing. Our data support OA and SNHL as a phenotype caused by dominant mutations in WFS1 in these additional eight families. Importantly, our data provide the first evidence that a single, recurrent mutation in WFS1, p.A684V, may be a common cause of ADOA and SNHL, similar to the role played by the p.R445H mutation in OPA1. Our findings suggest that patients who are heterozygous for WFS1 missense mutations should be carefully clinically examined for OA and other manifestations of Wolfram syndrome.
Full-text · Article · Jun 2011 · American Journal of Medical Genetics Part A
[Show abstract][Hide abstract] ABSTRACT: To identify the genetic etiology in a family with autosomal dominant progressive sensorineural hearing loss.
Prospective molecular genetic research study.
Academic genetic research laboratory.
Seventeen members of a family with dominant progressive nonsyndromic sensorineural hearing loss: 9 affected, 6 unaffected, and 2 spouses.
Clinical data from questionnaires, interviews, serial audiograms, and medical records; genetic data from genome-wide linkage analysis and candidate gene mutation analysis.
Symptoms, age at onset, serial audiometric data, and the presence or absence of a deafness-associated mutation.
Affected individuals in this family presented with autosomal dominant nonsyndromic high-frequency progressive sensorineural hearing loss, with age at onset ranging from 1 to 21 years. Genome-wide linkage analysis of single-nucleotide polymorphisms yielded evidence of linkage to an 18.9-Mb region on chromosome 1p34-p36, with a multipoint logarithm of odds score of 3.6. This interval contains a known deafness gene, KCNQ4, which underlies DNFA2 deafness. Sequencing of the 14 coding exons and intron-exon junctions of KCNQ4 revealed a novel heterozygous missense mutation, c.859G>C, p.Gly287Arg. The mutation disrupts the highly conserved GYG motif (glycine-tyrosine-glycine) of the phosphate-binding loop, hypothesized to be critical in maintaining pore structure and function. All 274 controls were negative for the mutation.
Autosomal dominant high-frequency hearing loss is genetically heterogeneous, and linkage analysis is an efficient means of identifying the etiology in larger families. Deafness in this family is caused by a novel mutation in KCNQ4.
Preview · Article · Jan 2011 · Archives of otolaryngology--head & neck surgery
[Show abstract][Hide abstract] ABSTRACT: Wolfram syndrome is characterized by optic atrophy, insulin dependent diabetes mellitus, diabetes insipidus and deafness. There are several other associated conditions reported in the literature, but congenital or early childhood cataracts are not among them.
Observational case series with confirmatory genetic analysis.
A pair of siblings, followed over 17 years, who manifest congenital or early childhood cataracts, diabetes insipidus, diabetes mellitus, optic atrophy, and deafness. They are both compound heterozygotes for mutations (V415 deletion and A684V substitution) in the WFS1 gene. Their father has congenital sensorineural hearing loss and developed optic atrophy. He is heterozygous for A684V in WFS1.
Wolfram syndrome should be in the differential diagnosis of genetic syndromes associated with congenital and early childhood cataracts. Here, we report on a mother who is a phenotypically normal carrier of an autosomal recessive Wolfram syndrome gene, and a father who has some of the findings of the syndrome and carries a single mutation that appears to be responsible for his hearing loss and optic atrophy. Their 2 children are compound heterozygotes and manifest the full Wolfram syndrome, in addition to cataracts.
No preview · Article · Dec 2010 · Ophthalmic Genetics
[Show abstract][Hide abstract] ABSTRACT: Auditory neuropathy is a rare form of deafness characterized by an absent or abnormal auditory brainstem response with preservation of outer hair cell function. We have identified Diaphanous homolog 3 (DIAPH3) as the gene responsible for autosomal dominant nonsyndromic auditory neuropathy (AUNA1), which we previously mapped to chromosome 13q21-q24. Genotyping of additional family members narrowed the interval to an 11-Mb, 3.28-cM gene-poor region containing only four genes, including DIAPH3. DNA sequencing of DIAPH3 revealed a c.-172G>A, g. 48G>A mutation in a highly conserved region of the 5' UTR. The c.-172G>A mutation occurs within a GC box sequence element and was not found in 379 controls. Using genome-wide expression arrays and quantitative RT-PCR, we demonstrate a 2- to 3-fold overexpression of DIAPH3 mRNA in lymphoblastoid cell lines from affected individuals. Likewise, a significant increase (approximately 1.5-fold) in DIAPH3 protein was found by quantitative immunoblotting of lysates from lymphoblastoid cell lines derived from affected individuals in comparison with controls. In addition, the c.-172G>A mutation is sufficient to drive overexpression of a luciferase reporter. Finally, the expression of a constitutively active form of diaphanous protein in the auditory organ of Drosophila melanogaster recapitulates the phenotype of impaired response to sound. To date, only two genes, the otoferlin gene OTOF and the pejvakin gene PJVK, are known to underlie nonsyndromic auditory neuropathy. Genetic testing for DIAPH3 may be useful for individuals with recessive as well as dominant inheritance of nonsyndromic auditory neuropathy.
Full-text · Article · Jul 2010 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: Molecular genetic testing is useful to differentiate otosclerosis from syndromic stapes ankylosis.
Congenital stapes ankylosis is genetically heterogeneous. Mutations in the NOG gene are known to be associated with a variety of rare stapes ankylosis syndromes including stapes ankylosis with broad thumbs and toes, multiple synostoses syndrome, and proximal symphalangism. These syndromes have overlapping clinical features that may be unrecognized.
The proband was a 54-year-old woman diagnosed in childhood with bilateral maximal conductive hearing loss. Audiologic, medical, and surgical records were reviewed. Deoxyribonucleic acid (DNA) was obtained from peripheral lymphocytes. DNA sequencing was used to assay for mutations in the NOG gene.
Clinical genetics evaluation was most consistent with proximal symphalangism, but features of multiple synostoses syndrome were identified as well. DNA sequencing revealed a heterozygous p.W205C mutation in the NOG gene, not found in 100 controls.
Evaluation of the patient with stapes ankylosis should include a family history and specific inquiry into features associated with stapes ankylosis syndromes, such as bony anomalies of the spine, hands, and feet. However, a negative family history does not exclude the possibility of a syndrome. Many patients who are thought to have nonsyndromic otosclerosis actually have syndromes caused by mutations in the NOG gene. Identifying a syndrome has implications for surgical management and prognosis.
No preview · Article · Jun 2009 · Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology
[Show abstract][Hide abstract] ABSTRACT: Insertional translocations (IT) are rare structural rearrangements. Offspring of IT balanced carriers are at high risk to have either pure partial trisomy or monosomy for the inserted segment as manifested by "pure" phenotypes. We describe an IT between chromosomes 3 and 13 segregating in a three-generation pedigree. Short tandem repeat (STR) segregation analysis and array-comparative genomic hybridization were used to define the IT as a 25.1 Mb segment spanning 13q21.2-q31.1. The phenotype of pure monosomy included deafness, duodenal stenosis, developmental and growth delay, vertebral anomalies, and facial dysmorphisms; the trisomy was manifested by only minor dysmorphisms. As the AUNA1 deafness locus on 13q14-21 overlaps the IT in the PCDH9 (protocadherin-9) gene region, PCDH9 was investigated as a candidate gene for deafness in both families. Genotyping of STRs and single nucleotide polymorphisms defined the AUNA1 breakpoint as 35 kb 5' to PCDH9, with a 2.4 Mb area of overlap with the IT. DNA sequencing of coding regions in the AUNA1 family and in the retained homologue chromosome in the monosomic patient revealed no mutations. We conclude that AUNA1 deafness does not share a common etiology with deafness associated with monosomy 13q21.2-q31.3; deafness may result from monosomy of PCHD9 or another gene in the IT, as has been demonstrated in contiguous gene deletion syndromes. Precise characterization of the breakpoints of the translocated region is useful to identify which genes may be contributing to the phenotype, either through haploinsufficiency or extra dosage effects, in order to define genotype-phenotype correlations.
Preview · Article · May 2009 · American Journal of Medical Genetics Part A
[Show abstract][Hide abstract] ABSTRACT: Autosomal-dominant sensorineural hearing loss is genetically heterogeneous, with a phenotype closely resembling presbycusis, the most common sensory defect associated with aging in humans. We have identified SLC17A8, which encodes the vesicular glutamate transporter-3 (VGLUT3), as the gene responsible for DFNA25, an autosomal-dominant form of progressive, high-frequency nonsyndromic deafness. In two unrelated families, a heterozygous missense mutation, c.632C-->T (p.A211V), was found to segregate with DFNA25 deafness and was not present in 267 controls. Linkage-disequilibrium analysis suggested that the families have a distant common ancestor. The A211 residue is conserved in VGLUT3 across species and in all human VGLUT subtypes (VGLUT1-3), suggesting an important functional role. In the cochlea, VGLUT3 accumulates glutamate in the synaptic vesicles of the sensory inner hair cells (IHCs) before releasing it onto receptors of auditory-nerve terminals. Null mice with a targeted deletion of Slc17a8 exon 2 lacked auditory-nerve responses to acoustic stimuli, although auditory brainstem responses could be elicited by electrical stimuli, and robust otoacoustic emissions were recorded. Ca(2+)-triggered synaptic-vesicle turnover was normal in IHCs of Slc17a8 null mice when probed by membrane capacitance measurements at 2 weeks of age. Later, the number of afferent synapses, spiral ganglion neurons, and lateral efferent endings below sensory IHCs declined. Ribbon synapses remaining by 3 months of age had a normal ultrastructural appearance. We conclude that deafness in Slc17a8-deficient mice is due to a specific defect of vesicular glutamate uptake and release and that VGLUT3 is essential for auditory coding at the IHC synapse.
Full-text · Article · Aug 2008 · The American Journal of Human Genetics