[The clinical application of gene diagnosis and genetic counseling on hereditary hearing loss]

Objective:To summarize the clinic procedure and experience about gene diagnosis and genetic counseling on hereditary hearing loss, and explore the strategy and principle about gene diagnosis and genetic counseling on hereditary hearing loss.Method:A retrospective analysis was used on the clinical data of 151 cases who aim at genetic counseling. The all cases were divided into 5 groups according to the purpose of genetic counseling, such as the occurrence risk of hearing loss, the etiological analysis, the choice of the intervention way, the examination guidance, the prevention of hearing loss and the usage requirement of Aminogly cosides drugs. The counseling procedure includes the investigation of the etiology and family history, drawing the family pedigree, general physical examination, auditory examination and genetic analysis. Sanger sequencing analysis and/or Targeted nextgeneration sequencing was utilized to detect the deaf-gene mutations. At last, the genetic counseling, fertility guidance and prenatal diagnosis will be made on the basis of the results of gene detection. Result:There are 33 newborns who did not pass the deafgene screening, 9 of them could be diagnosed definitely as hereditary hearing loss, and the other 24 were the carriers of deafgene mutation. Eighty of 104 deaf patients were diagnosed definitely as hereditary hearing loss and the related gene mutation was found. Six objects in the 10 patients with auditory neuropathy are diagnosed as OTOF or SLC17A8 gene mutations before cochlear implantation. Three of 7 reproductive age objects who had family history were recessive deaf-gene carriers, 2 of them carried the same target gene with the mate who receive our fertility guidance and prenatal diagnose. The other 1 object carried the dominant genetic mutation(incomplete dominant heredity). There were 4 pregnant women who did not pass the deaf-gene screening, 1 of them carry the same target gene with the mate. The populations who want to use Aminoglycosides drugs were not diagnosed as carrying any related mitochondrial gene mutation. We carried out the genetic counseling according to the results of gens detection and clinical phenotype.Conclusion:Genetic counseling is based on the different purpose. The analysis of gene diagnosis should be considered to combine with the clinical phenotype. The principle of choosing the objects to make a gene diagnosis includes: ①the all deaf-genes sequencing was applied for the deaf patients. ② the screening target gene sequencing was used for the newborns who did not pass the deaf-gene screening and the mate whose pregnant wife did not pass the deafgene screening. ③the specific target gene sequencing could be used for the patients who has a clear family history or specific phenotype.

[Effects of exogenous brain-derived neurotrophic factor on the morphology and function of cochlea in the animal model of hereditary hearing loss]

Objective:To study the effect of early administration exogenous BDNF on the morphology and function of conditional knockout Cx26 mice cochlea.Method:Conditional knockout Cx26 mice was chosen as animal model, early after birth (P0-P2) exogenous BDNF (rAAV mediated BDNF plasmid, AAV-BDNF) was injected through scala media. Expression of BDNF in the cochlea was observed by western-blot, the growth promoting effect of nerve fibers was detected by IHC; 2 m after injection, the protective effect of BDNF on corti and spiral ganglion cells were detected by resin section; animal hearing were tested by ABR.Result:①Exogenous BDNF could be well expressed in the inner ear; ②Exogenous BDNF has a good effect on the growth of cochlea nerve fiber; ③Exogenous BDNF could protect the morphology of organ of corti; to count the number of spiral ganglion cells, using the density value of top-turn in non-injected ear as the standard unit, the values of middle and basal turn in injected ear were 0.81±0.02, 0.65±0.02, compared with non-injected ears, both statistically significant difference could be found, indicates that exogenous BDNF can effectively improve the number of spiral ganglion cells. ④By calculating the ABR threshold of different frequencies of the injected and non-injected ear, there was no statistical difference between them. Indicates that exogenous BDNF has no effect on improving the function of cochlea.Conclusion:The protective effect of early administration exogenous BDNF was effective in the cochlea and spiral ganglion cells of conditional knockout Cx26 mice, but no protective effect for auditory function.