Dai Pu

GJB2 mutation spectrum in deaf population in a typical southeastern area of China

Mutations in GJB2 gene are the most frequently found mutations in patients with nonsyndromic hearing impairment. However, the spectrum and prevalence of mutations in this gene vary among different ethnic groups. In China, 30,000 infants are born with congenital hearing impairment annually. In order to provide appropriate genetic testing and counseling to the families, we investigated the molecular etiology of nonsyndromic deafness in 103 unrelated school children attending Nantong School for the Deaf and Mute in Jiangsu Province, China. The coding exon of the GJB2 gene was PCR amplified and sequenced. Sixty two GJB2 mutant alleles were identified in 35.9% (37/103) of the patients. Twenty five patients carried two pathogenic mutations and 12 patients carried one mutant allele. The 235delC was the most common mutation accounting for 69.4% (43/62) of GJB2 mutant alleles. The GJB2 mutant alleles accounted for 30.1% (62/206) of all chromosomes responsible for nonsyndromic hearing impairment. Testing of the 3 most prevalent deleterious frame shift mutations in this cohort detected 100% of all GJB2 mutant alleles. These results demonstrate that an effective genetic testing of GJB2 gene for patients and families with nonsyndromic hearing impairment is possible.

Congenital cholesteatoma of the middle ear – a report of 10 cases

Abstract Objectives To study clinical, imaging features and treatment outcomes of congenital cholesteatoma of middle ear (CCME). Methods This is a retrospective review of 10 CCME cases selected from 952 cholesteatoma cases treated between January 1995 and December 2005 at the Department of Otolaryngology-Head and Neck Surgery, Chinese PLA General Hospital. The main outcome measures were the site of origin, clinical features, surgical findings, imaging characteristics and hearing results. Results The mean age of the 10 patients was 16 years(ranged from 10 to 24 years), with 6 being older than 18 years. There were 7 males and 3 females. The average delay to diagnosis was longer than 2 years. The mean preoperative PTA was 55 dB HL, with a mean ABG of 45 dB. Typical cholesteatomas were seen behind the tympanic membrane in the superoposterior quadrant on otoscopy only in 2 patients. High resolution CT was completed in all patients. Most of the patients(8/10) were diagnosed with otosclerosis or ossicular abnormality before operation. All patients underwent a one-stage tympanoplasty following transmeatal explorative tympanotomy and complete cholesteatoma removal, except one, who underwent a CWU mastoidectomy due to extensive cholesteatoma involvement. The choleasteatoma lesion was confined to the superoposterior mesotympanum in all patients. The mean postoperative PTA was 20 dB HL. All patients were followed-up for at least 1.5 years postoperatively. Revision procedures were performed in 2 patients for hearing deterioration. No residual or recurrence of cholesteatoma was found. Conclusion CCME is a rare disease that often gets delayed diagnosis. Residual lesions and the prognosis mainly depend on the extent of the lesion.

Prevalence of the GJB2 Mutations in Deafness Patients of Different Ethnic Origins in Xinjiang

Abstract Objective To investigate GJB2 mutation prevalences in the Uigur and Han ethnic groups in Xinjiang, China, and determine the relationship between ethnicity and GJB2 gene mutations. Methods Information regarding ethnicity of patients’ families was obtained through medical records review and/or patient interview. Blood samples were collected from 61 Uigurs and 66 Hans for direct sequencing of the coding region and intron/exon boundaries of the GBJ2 gene. Results Carrier frequency of GJB2 mutations was similar between the Uigur and Han subjects. The GJB2 35delG mutation was seen only in Uigur patients with hearing loss, whereas the 235delC mutation was identified in both Uigur and Han patients. The allelic Frequency of 35delG mutation was 7.4% (9/122) in Uigur deaf students, but none in Han deaf students (0/128) and Uigur controls (0/196). The allelic frequency of GJB2 235delC mutation in Uigur and Han deaf students was 5.7% and 9.8%, and that of 299-300delAT mutation was 0.8% and 5.5%, respectively. V27I and E114G were the most frequent types of polymorphism. Conclusion We found an Asian-specific GJB2 diversity among Uigurs, and comparable GJB2 contribution to deafness in Uigur and Han patients. The high carrier frequency of 35delG in Uigurs (11.5%) is probably defined by gene drift/founder effect in a particular group. Even though GJB2 mutations have been widely reported in the literature, this discussion represents the first report of GJB2 mutations in Chinese multi-ethnic populations.

Mitochondrial DNA A1555G mutation screening using a testing kit method and its significance in preventing aminoglycoside-related hearing loss

Abstract To report a new screening method for mitochondrial DNA 1555A→G mutation and the results of genotype analysis in 19 maternal inherited deafness pedigrees. Method Five hundred and forty-six non-syndromic neuro-sensory hearing loss patients were tested for 1555A→G mutation using a new compact testing kit, which allows clear distinction between wild type and 1555 A→G mutated mtDNAs. Results Nineteen subjects among the 546 patients (3.48%) were found to carry mtDNAA1555G mutation. The results were confirmed by sequencing in an ABI 3100 Avant sequencer. Conclusions Maternal inherited deafness families are a frequently seen in outpatient group. The detection of mtDNA 1555 A→G mutation with a low cost, ready to use detection kit is needed and suitable in China for large scale screening and preventive testing before usage of aminoglycoside antibiotics.