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Objective: The purpose of this review was to evaluate the current literature on phosphoribosylpyrophosphate synthetase 1 (PRPS1)-related diseases and their consequences on hearing function., Design: A literature search of peer-reviewed, published journal articles was conducted in online bibliographic databases., Study Sample: Three databases for medical research were included in this review., Results: Mutations in PRPS1 are associated with a spectrum of non-syndromic to syndromic hearing loss. Hearing loss in male patients with PRPS1 mutations is bilateral, moderate to profound, and can be prelingual or postlingual, progressive or non-progressive. Audiogram shapes associated with PRPS1 deafness are usually residual and flat. Female carriers can have unilateral or bilateral hearing impairment. Gain of function mutations in PRPS1 cause a superactivity of the PRS-I protein whereas the loss-of-function mutations result in X-linked nonsyndromic sensorineural deafness type 2 (DFN2), or in syndromic deafness including Arts syndrome and X-linked Charcot-Marie-Tooth disease-5 (CMTX5)., Conclusions: Lower residual activity in PRS-I leads to a more severe clinical manifestation. Clinical and molecular findings suggest that the four PRPS1 disorders discovered to date belong to the same disease spectrum. Dietary supplementation with S-adenosylmethionine (SAM) appeared to alleviate the symptoms of Arts syndrome patients, suggesting that SAM could compensate for PRS-I deficiency.

Objective: We have characterized the spectrum of SLC26A4 mutations and clinical features in a population of mainland Chinese patients with nonsyndromic sensorineural hearing loss (SNHL) and enlarged vestibular aqueduct (EVA)., Study Design: Cross-sectional clinical genetic study., Setting: Tertiary care outpatient otolaryngology clinic., Methods: A total of 32 subjects identified with bilateral EVA using high-resolution CT were screened for mutations in SLC26A4 by denaturing high-performance liquid chromatography and direct sequencing methods., Results: A total of 13 different mutations were identified in the SLC26A4 gene, five of which are novel. A total of 88 percent of the patients harbored biallelic mutations, 11 patients were homozygotes, and 17 were compound heterozygotes. Four patients were found to carry a single SLC26A4 mutation. The IVS7-2A>G mutation was the most frequent, accounting for 60 percent of the mutant alleles. We have not found any correlations between the type of SLC26A4 mutations and the type, degree, and progression of hearing loss. There are significant proportions of patients with asymmetric (26%), progressive (32%), or fluctuating hearing loss (21%)., Conclusion: Our data confirm the high prevalence of SLC26A4 mutations in Chinese patients with SNHL and EVA. We could not establish any relationship between genotype and phenotype. However, the high incidence of asymmetric, progressive, and fluctuating hearing loss found in the current study indicates that patients with those features should be routinely screened for SLC26A4 mutation in addition to diagnosis of EVA using CT or MRI.

Objective: To investigate the mutational of the coagulation factor C homology (COCH) gene related to autosomal dominant sensorineural nonsyndromic hearing loss (DFNA) with late onset in Chinese population., Methods: Peripheral blood samples were collected from he members of 26 DFNA families, members of 19 small DFNA families with un recognized inheritance pattern, and 22 sporadic patients with sensorineural nonsyndromic late onset hearing loss, the hearing loss of all of which occurred during the age range 10 - 40, and 100 normal controls. From different parts of China, these subjects underwent questionnaire survey too. Genomic DNA was isolated, COCH mutation was screened by PCR and sequencing, and restriction endonuclease analysis was used to detect the mutation sites of the COCH gene. The conservation in evolution of the target amino acid sequences was analyzed using CluatalX1.82 software., Results: DNA sequencing of coding regions and exon/intron boundaries of COCH 2 - 12 exons identified a heterozygous G-to-A substitution at position 1625 in exon 12 in a large DFNA family, leading to a C542Y substitution, and a heterozygous T-to-C substitution at position 1535 in exon 12 in a small family, leading to a M512T substitutions. Both the residues of Cys542 and M512 were conserved across human, mouse, chicken, and zebrafish. These mutations were not detected in the 100 control subjects., Conclusion: The C542Y and the M512T mutations cause hearing loss in Chinese DFNA families.

Objective: To analyze the sequence of GJB2 gene in nonsyndromic hearing impairment (NSHI) patients in China., Methods: Peripheral blood samples were obtained from 1190 NSHI patients randomly selected from the Deaf and Mute Schools of Beijing, Hebei, Heilongjiang, Jilin, Inner Mongolia, Shanxi, Henan, Hubei, Shaanxi, Gansu, Ningxia, Qinghai, Anhui, Jiangsu, Shanghai, Fujian, Guangdong, and Guangxi, and 301 children with normal hearing level used as controls. Genomic DNA was extracted by extraction kits to undergo polymerase chain reaction and sequencing so as to detect the mutations of GJB2 gene., Results: Sixteen pathogenic mutations of GJB2 gene were found, the most common of which included 235delC, 299-300delAT, and 176del16bp. 250 patients (21.05%) carried definite GJB2 mutations, 245 of which (98%) carried at least one of these 3 common mutations. 222 of the 250 patients (88.80%) carried the mutation 235delC with a detection rate of 18.66%. 62 of the 250 patients (24.80%) carried the mutation 299-300delAT with a detection rate of 5.21%. 19 of the 250 patients (7.60%) carried the mutation 176del16bp with a detection rate of 1.60%. The detection rates of these 3 mutations in the NSHI patients were all significantly higher than those among the controls (all P<0.01)., Conclusion: The hot spot of GJB2 gene mutations in Chinese NSHI patients is 235delC, followed by 299-300delAT and 176del16bp. These results establish a fundamental basis for drawing a spectrum of GJB2 gene mutation among Chinese population.

Objective: To analyze the clinical features of audiological and vestibular function in a Chinese family with late onset autosomal dominant nonsyndromic sensorineural hearing loss., Methods: Comprehensive audiological and vestibular evaluation including pure tone audiometry, auditory brainstem response (ABR), electrocochleogram (EcochG), oculomotor testing, caloric tests, rotational testing, computerized dynamic posturography and vestibular evoked myogenic potentials (VEMP) were conducted to identify the hearing and vestibular impairment., Results: All affected family members shared sensorineural hearing loss with full penetrance starting between the second and fifth decade of life as a high frequency loss which progresses to a severe to profound loss at the sixth to seventh decade. The extensive vestibular evaluation indicated that all affected members performed normally in computerized dynamic posturography and caloric testing. Impairment of the saccular otolith in all of six affected members was suggested by results of the VEMP test. The velocity step test generated abnormal time constants and sinusoidal oscillation test generated abnormal gains and phase in affected members indicated that horizontal canal vestibular hyporeflexia in history. All affected subjects examined in this family showed completely normal ocular motor responses in oculomotor testing, including smooth pursuit, optokinetic nystagmus, gaze and saccade., Conclusions: The predominant feature of the Chinese DFNA9 family was that all the affected subjects harboring COCH mutation in the vWFA2 domain didn't suffer the vestibular symptoms during their life time and comprehensive vestibular assessment revealed only subtle vestibular hypofunction in affected members of this family. There is a genotype-phenotype correlation in DFNA9.

Objective: To explore the necessity of large-scale screening of mtDNA A1555G mutation in prevention of aminoglycoside antibiotic induced deafness (AAID) and to develop a feasible method to prevent AAID., Methods: A total of 1836 patients with non-syndromic hearing impairment (NSHI), 1352 students of schools for deaf-mutes in 11 provinces and municipality in China, 413 out-patients, and 71 persons from the families with maternal relatives suffering from AAID, underwent questionnaire survey and/or PCR for A-to-G mutation at nucleotide 1555 of the mitochondrial genome., Results: Sixty three patients with mtDNA A1555G mutation were found among the 1836 NSHI patients. Fifty-two maternal pedigrees were identified. 536 cases with normal hearing from these pedigrees were informed to avoid using aminoglycoside antibiotics (AmAn)., Conclusion: Large-scale screening of mtDNA A1555G mutation and relevant health education to avoid use of AmAn are effective to prevent ototoxicity in the A1555G carriers and their maternal relatives.