Clinical GeneticsVolume 73, Issue 4 p. 391-394 Novel mutations in the vWFA2 domain of COCH in two Chinese DFNA9 families HJ Yuan, HJ Yuan Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, China These authors contributed equally to this work.Search for more papers by this authorDY Han, DY Han Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, China These authors contributed equally to this work.Search for more papers by this authorQ Sun, Q Sun Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorD Yan, D Yan Department of Otolaryngology (D-48), University of Miami, Miami, FL, USASearch for more papers by this authorHJ Sun, HJ Sun Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorR Tao, R Tao Bio-X Life Science Research Center, Shanghai Jiao Tong University, Shanghai, ChinaSearch for more papers by this authorJ Cheng, J Cheng Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorW Qin, W Qin Bio-X Life Science Research Center, Shanghai Jiao Tong University, Shanghai, ChinaSearch for more papers by this authorS Angeli, S Angeli Department of Otolaryngology (D-48), University of Miami, Miami, FL, USASearch for more papers by this authorXM Ouyang, XM Ouyang Department of Otolaryngology (D-48), University of Miami, Miami, FL, USASearch for more papers by this authorSZ Yang, SZ Yang Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorL Feng, L Feng Institute of Mental Health, Peking University, Beijing, ChinaSearch for more papers by this authorJY Cao, JY Cao Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorGY Feng, GY Feng Bio-X Life Science Research Center, Shanghai Jiao Tong University, Shanghai, ChinaSearch for more papers by this authorYF Wang, YF Wang Institute of Mental Health, Peking University, Beijing, ChinaSearch for more papers by this authorP Dai, P Dai Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorSQ Zhai, SQ Zhai Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorWY Yang, WY Yang Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorL He, L He Bio-X Life Science Research Center, Shanghai Jiao Tong University, Shanghai, ChinaSearch for more papers by this authorXZ Liu, Corresponding Author XZ Liu Department of Otolaryngology (D-48), University of Miami, Miami, FL, USADr Xue Zhong LiuDepartment of Otolaryngology (D-48)University of Miami1666 NW12th AvenueMiamiFL 33136USATel.: 305-243-5695Fax: 305-243-4925e-mail: xliu@med.miami.eduSearch for more papers by this author HJ Yuan, HJ Yuan Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, China These authors contributed equally to this work.Search for more papers by this authorDY Han, DY Han Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, China These authors contributed equally to this work.Search for more papers by this authorQ Sun, Q Sun Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorD Yan, D Yan Department of Otolaryngology (D-48), University of Miami, Miami, FL, USASearch for more papers by this authorHJ Sun, HJ Sun Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorR Tao, R Tao Bio-X Life Science Research Center, Shanghai Jiao Tong University, Shanghai, ChinaSearch for more papers by this authorJ Cheng, J Cheng Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorW Qin, W Qin Bio-X Life Science Research Center, Shanghai Jiao Tong University, Shanghai, ChinaSearch for more papers by this authorS Angeli, S Angeli Department of Otolaryngology (D-48), University of Miami, Miami, FL, USASearch for more papers by this authorXM Ouyang, XM Ouyang Department of Otolaryngology (D-48), University of Miami, Miami, FL, USASearch for more papers by this authorSZ Yang, SZ Yang Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorL Feng, L Feng Institute of Mental Health, Peking University, Beijing, ChinaSearch for more papers by this authorJY Cao, JY Cao Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorGY Feng, GY Feng Bio-X Life Science Research Center, Shanghai Jiao Tong University, Shanghai, ChinaSearch for more papers by this authorYF Wang, YF Wang Institute of Mental Health, Peking University, Beijing, ChinaSearch for more papers by this authorP Dai, P Dai Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorSQ Zhai, SQ Zhai Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorWY Yang, WY Yang Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, ChinaSearch for more papers by this authorL He, L He Bio-X Life Science Research Center, Shanghai Jiao Tong University, Shanghai, ChinaSearch for more papers by this authorXZ Liu, Corresponding Author XZ Liu Department of Otolaryngology (D-48), University of Miami, Miami, FL, USADr Xue Zhong LiuDepartment of Otolaryngology (D-48)University of Miami1666 NW12th AvenueMiamiFL 33136USATel.: 305-243-5695Fax: 305-243-4925e-mail: xliu@med.miami.eduSearch for more papers by this author First published: 28 February 2008 https://doi.org/10.1111/j.1399-0004.2008.00972.xCitations: 23 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume73, Issue4April 2008Pages 391-394 RelatedInformation

Conclusions. Significant difference in the incidence of mitochondrial DNA (mtDNA) mutations was found between the Chinese and USA populations. The identification of the mtDNA A1555G mutation in a large proportion of Chinese probands with nonsyndromic sensorineural hearing loss (NSHL) provides a molecular explanation for the high prevalence of aminoglycoside-induced deafness in China. Objective. The aim was to characterize the audiological and genetic features of NSHL due to mutations in mtDNA. Subjects and methods. The mtDNA and audiogram analyses were performed in 498 NSHL patients (290 from China and 208 from the USA) with and without history of aminoglycoside exposure. A PCR and restriction enzyme digestion protocol was used for mutational screening and the European Workshop on Genetic Hearing Loss criteria were applied for audiological classification. Results. All Chinese probands (15.5%) with mtDNA mutation were found to carry the homoplasmic mtDNA A1555G mutation, whereas four probands (1.9%) from the USA were found to carry the mtDNA A1555G and two (1%) had mtDNA G7444A. Approximately 63% of the probands with mtDNA mutations had post-lingual hearing loss and 56.8% of them had a medical history of exposure to aminoglycosides. Hearing losses are bilateral, sensorineural, and symmetric. The main audiogram shapes found were sloping.

We report here the clinical, genetic, and molecular characteristics of a large Chinese family exhibiting non-syndromic, late-onset autosomal dominant sensorineural hearing loss. Clinical evaluation revealed variable phenotypes of hearing loss in terms of severity and age-at-onset of disease in these subjects. Genome-wide linkage analysis mapped the disease gene to the DFNA5 locus with a maximum two-point log odds score of 5.39 at [theta] = 0 for marker D7S2457. DNA sequencing of DFNA5 revealed a novel heterozygous IVS8+4 A > G substitution in the splice donor site of intron 8. Reverse transcriptase-polymerase chain reaction (RT-PCR) showed skipping of exon 8 in the mutant transcript. This mutation faithfully cosegregated with hearing loss in the family. In addition, the mutation was absent in 100 unrelated control DNA samples of Chinese origin. The IVS8+4 A > G mutation is predicted to create a shift in the reading frame and introduce a stop codon at position 372, thereby resulting in a prematurely truncated DFNA5 protein. Up to date, a total of four mutations in DFNA5 have been reported to lead to hearing impairment, all of them result in skipping of exon 8 at the mRNA level. Our findings provide further support for the hypothesis that DFNA5-associated hearing loss is caused by a very specific gain-of-function mutation.

The driving forces for the regulation of cell morphology are the Rho family GTPases that coordinate the assembly of the actin cytoskeleton. This dynamic feature is a result of tight coupling between the cytoskeleton and signal transduction and is facilitated by actin-binding proteins (ABPs). Mutations in the actin bundling and PDZ domain-containing protein harmonin are the causes of Usher syndrome type 1C (USH1C), a syndrome of congenital deafness and progressive blindness, as well as certain forms of non-syndromic deafness. Here, we have used the yeast two-hybrid assay to isolate molecular partners of harmonin and identified DOCK4, an unconventional guanine exchange factor for the Rho family of guanosine triphosphatases (Rho GEF GTPases), as a protein interacting with harmonin. Detailed molecular analysis revealed that a novel DOCK4 isoform (DOCK4-Ex49) is expressed in the brain, eye and inner ear tissues. We have further provided evidence that the DOCK4-Ex49 binds to nucleotide free Rac as effectively as DOCK2 and DOCK4 and it is a potent Rac activator. By immunostaining using a peptide antibody specific to DOCK4-Ex49, we showed its localization in the inner ear within the hair bundles along the stereocilia (SC). Together, our data indicate a possible Rac-DOCK4-ABP harmonin-activated signaling pathway in regulating actin cytoskeleton organization in stereocilia.

BACKGROUND:Non-syndromic hearing loss is among the most genetically heterogeneous traits known in humans. To date, at least 50 loci for autosomal dominant non-syndromic sensorineural hearing loss (ADNSSHL) have been identified by linkage analysis.OBJECTIVE:To report the mapping of a novel autosomal dominant deafness locus on the long arm of chromosome 14 at 14q11.2-q12, DFNA53, in a large multigenerational Chinese family with post-lingual, high frequency hearing loss that progresses to involve all frequencies.RESULTS:A maximum multipoint LOD score of 5.4 was obtained for marker D14S1280. The analysis of recombinant haplotypes mapped DFNA53 to a 9.6 cM region interval between markers D14S581 and D14S1021. Four deafness loci (DFNA9, DFNA23, DFNB5, and DFNB35) have previously been mapped to the long arm of chromosome 14. The critical region for DFNA53 contains the gene for DFNA9 but does not overlap with the regions for DFNB5, DFNA23, or DFNB35. Screening of the COCH gene (DFNA9), BOCT, EFS, and HSPC156 within the DFNA53 interval did not identify the cause for deafness in this family.CONCLUSIONS:Identifying the DFNA53 locus is the first step in isolating the gene responsible for hearing loss in this large multigeneration Chinese family.

Mutations in genes coding for cadherin 23 and protocadherin 15 cause deafness in both mice and humans. Here, we provide evidence that mutations at these two cadherin loci can interact to cause hearing loss in digenic heterozygotes of both species. Using a classical genetic approach, we generated mice that were heterozygous for both Cdh23 and Pcdh15 mutations on a uniform C57BL/6J background. Significant levels of hearing loss were detected in these mice when compared to age-matched single heterozygous animals or normal controls. Cytoarchitectural defects in the cochlea of digenic heterozygotes, including degeneration of the stereocilia and a base-apex loss of hair cells and spiral ganglion cells, were consistent with the observed age-related hearing loss of these mice beginning with the high frequencies. In humans, we also have obtained evidence for a digenic inheritance of a USH1 phenotype in three unrelated families with mutations in CDH23 and PCDH15. Altogether, our data indicate that CDH23 and PCDH15 play an essential long-term role in maintaining the normal organization of the stereocilia bundle.

OBJECTIVE., To determine the etiology of adult-onset sensorineural hearing loss.STUDY DESIGN AND SETTING: This is a prospective cohort study of 60 adult subjects with bilateral sensorineural hearing loss of no obvious etiology by medical history and physical examination. These patients were evaluated at an academic medical center and underwent evaluation by high-resolution computed tomography of the temporal bone, autolmmune panel, and DNA testing for mutations of both the GJB2 gene and the mitochondrial DNA (1555A > G and 7445A > G).RESULTS: An etiologic diagnosis was achieved in 6 patients: cochlear otosclerosis, 1 case; dilated vestibular aqueduct, 1 case; a mitochondrial DNA 7445A > G mutation, 3 cases; and a mitochondrial DNA 1555A > G mutation, 1 case. CONCLUSION: This result underscores the importance of a search for the etiology of a hearing deficit in adult patients. There are specific interventions now available for the management of hearing-impaired patients with cochlear otosclerosis and mitochondrial DNA mutations.

Usher syndrome type II is an autosomal recessive disorder characterized by moderate to severe hearing impairment and progressive visual loss due to retinitis pigmentosa (RP). We carried out a mutation screening of the USH2A gene in 88 probands with Usher syndrome type II to determine the frequency of USH2A mutations as a cause for USH2. Six mutations, including 2299delG, 921‐922insCAGC, R334W, N346H, R626X, and N357T were identified, with 2299delG mutation being the most frequent (16.5% of alleles), accounting for 77.5% of the pathologic alleles. Thirty‐five percent (31/88) of the probands had a USH2A mutation. Nine of them carried two pathogenic mutations: six cases were homozygotes and three were compound heterozygotes. Twenty‐two probands (25%) were found to carry only single USH2A mutations. One new missense mutation (N357T) occuring within the laminin N‐terminal (type VI) domain of usherin was identified. Eight polymorphisms were found, five of which are novel. Our data support the view that the 2299delG is the most common mutation in USH2A.

Prestin, a membrane protein that is highly and almost exclusively expressed in the outer hair cells (OHCs) of the cochlea, is a motor protein which senses membrane potential and drives rapid length changes in OHCs. Surprisingly, prestin is a member of a gene family, solute carrier (SLC) family 26, that encodes anion transporters and related proteins. Of nine known human genes in this family, three (SLC26A2, SLC26A3 and SLC26A4) are associated with different human hereditary diseases. The restricted expression of prestin in OHCs, and its proposed function as a mechanical amplifier, make it a strong candidate gene for human deafness. Here we report the cloning and characterization of four splicing isoforms for the human prestin gene (SLC26A5a, b, c and d). SLC26A5a is the predominant form of prestin whereas the others showed limited distribution associated with certain developmental stages. Based on the functional importance of prestin we screened for possible mutations involving the prestin gene in a group of deaf probands. We have identified a 5'-UTR splice acceptor mutation (IVS2-2A>G) in exon 3 of the prestin gene, which is responsible for recessive non-syndromic deafness in two unrelated families. In addition, a high frequency of heterozygosity for the same mutation was observed in these subjects, suggesting the possibility of semi-dominant influence of the mutation in causing hearing loss. Finally, the observation of this mutation only in the Caucasian probands indicated an association with a specific ethnic background. This study thereby reveals an essential function of prestin in human auditory processing.

Usher syndrome (USH) is characterized by the associated findings of hearing loss and retinitis pigmentosa (RP), leading to progressive loss of vision. Three forms of USH can be distinguished clinically. In the most severe form, USH1, profound congenital deafness is associated with vestibular dysfunction and RP. To determine the frequency of USH1C mutations as a cause for USH1, 128 probands with Usher syndrome type 1 including seven from Acadian and 121 from non‐Acadian populations were systematically screened for mutations in USH1C using a combined single‐strand conformational polymorphisms (SSCP)/heteroduplex and sequencing method. All seven Acadian USH1 patients were found to be homozygous for both the 216G>A mutation and the 9‐repeat VNTR which characterizes the Acadian allele, confirming previous evidence for a founder effect by haplotype analysis. However, USH1C mutations were identified in only two non‐Acadian USH1 probands (1.65%) including one from Pakistan who was homozygous for a 238‐239insC mutation and one from Canada was also homozygous for the Acadian allele. The low prevalence of USH1C mutations in the present study suggests that the high prevalence of the 238‐239insC in Germany may reflect a founder effect. Comparison of the affected haplotypes in the Canadian patient with the Acadian USH1 patients yielded evidence for a founder effect. Our data suggest that USH1C is a relatively rare form of USH1 in non‐Acadian populations and that in addition to the 216G>A Acadian mutation, the 238‐239insC mutation appears to be common in some populations.

Mutations in four members of the connexin gene family have been shown to underlie distinct genetic forms of deafness, including GJB2 [connexin 26 (Cx26)], GJB3 (Cx31), GJB6 (Cx30) and GJB1 (Cx32). We have found that alterations in a fifth member of this family, GJA1 (Cx43), appear to cause a common form of deafness in African Americans. We identified two different GJA1 mutations in four of 26 African American probands. Three were homozygous for a Leu-->Phe substitution in the absolutely conserved codon 11, whereas the other was homozygous for a Val-->Ala transversion at the highly conserved codon 24. Neither mutation was detected in DNA from 100 control subjects without deafness. Cx43 is expressed in the cochlea, as is demonstrated by PCR amplification from human fetal cochlear cDNA and by RT-PCR of mouse cochlear tissues. Immunohistochemical staining of mouse cochlear preparations showed immunostaining for Cx43 in non-sensory epithelial cells and in fibrocytes of the spiral ligament and the spiral limbus. To our knowledge this is the first alpha connexin gene to be associated with non-syndromic deafness. Cx43 must also play a critical role in the physiology of hearing, presumably by participating in the recycling of potassium to the cochlear endolymph.