Analysis of genotypes and hearing phenotypes of mutation infants with deafness

Objective:The aim of this study is to explore the genotype and hearing phenotype of deaf infants with mutation of GJB2 gene. Method:Subjects were 121 infants with GJB2 gene mutations who were treated in the Children's Hearing Diagnosis Center of Beijing Tongren hospital. All subjects were accepted to undertake the universal newborns hearing screeningUNHS and series of objective audiometry, including auditory brainstem response, distortion product otoacoustic emission, auditory steady-state response and other audiological tests. All subjects were screened for nine pathogenic variants in four genes or all exons of the GJB2 gene, and then were diagnosed as infants with GJB2 gene mutations. Initially, analyzing their genotypes and hearing phenotypes generally. Then, the subjects were divided into two groups according to the genotypes: T/T grouptruncated/truncated mutations, 89 cases and T/NT grouptruncated/non-truncated mutations, 32 cases. Chi-square test was used to analyze the results of UNHS, hearing degree, audiogram patterns and symmetry/asymmetry of binaural hearing phenotype. Eventually, analyzing the results of UNHS. Result:The most common truncated mutation was c.235delC64.88%, 157/242 and the most common non-truncated mutation was c.109G>A11.16%, 27/242. The homozygous mutation of c.235delC/c.235delC was the dominant in T/T group38.84%, 47/121, and the compound heterozygous mutation of c.235delC/c.109G>A was the dominant in T/NT group18.18%, 22/121. 81.82%99/121 of subjects failed in UNHS, including 74.38%90/121 with bilateral reference, 7.44%9/121 with a single pass. The refer rate of UNHS of group T/T and T/NT were 86.52%77/89 and 68.75%, respectively. There was a statistically significant difference between the two groupsP 0.05. Conclusion:In this study, c.235delC/c.235delC homozygous mutation was dominant in T/T group and c.235delC/c.109G>A heterozygous mutation was dominant in T/NT Group. The hearing phenotypes in T/T group were mostly bilateral asymmetric severe hearing loss, and those in T/NT Group were bilateral symmetric mild to moderate hearing loss, special attention should be paid to the audiological characteristics of different genotypes.