Hearing Conditions Of Centenarians And Analysis Of Causal Gene In A Chinese Hereditary Hearing Loss Pedigree

With the development of social medical business, the number of centenarians was evidently increasing. The life quality of centenarians has brought more and more concerns. Presbycusis is common in people above 60y and can greatly affect living quality of the senile. It has been proved that heaing loss will lead to psychological and physiological diseases. In our study, we collected the heaing information of centenarians and found that almost all centenarians suffered serious hearing loss which provide basis for heaing health protection and prevention of centenarians.The identification of pathogenic gene for non-syndromic deafness patients is an main direction of hearing genetics in the rencent 20 years. The speed has accelerated quickly since the widespread use of Next Generation Sequencing (NGS).146 hearing loss gene loci have been identified and 76 non-syndromic deafness gene was found until now. Gene GJB2、SLC26A4、mitochondrial 12SrRNA were known as the most common hearing loss genes in China and have been detected as hearing screening in many hospitals. The carrying rate of the three genes is different in different districts and nations according to previous researches. Our study revealed the carrying rate of the three genes in Linyi district of Shandong province. Also, we used the whole exome sequening technology to identify the causal gene in a autosomal recessive hereditary hearing loss pedigree containing two patients and gain some experience.Part one Clinical observation on hearing conditions of centenarians in northern district of ChinaTo further understand the hearing health of centenarians and hunt for more methods to assess it.54 centenarians in Rizhao and Linyi Districts in Shandong Province were investigated to assess the hearing health of centenerians comprehensively by questionnaire investigaton, performing pure tone audiometry, acoustic immitance, intelligence evaluation and Speech detection score.135 individuals designed as hearing threshold controls were divided into four groups aged between 45～59,60～69.70～79,80～89 years. We found that the hearing threshold of centenarians was obviously higher than control groups (p< 0.05) and all the centenarians suffered moderate to profound hearing loss according to the World Health Organization(WHO) criterions. Few centenarians have normal speech detection rate. The hearing threshold of male centenarians at 8000Hz is higher than female (P=0.047). So the hearing health of centenarians is not optimistic. Almost all centenarians suffered serious hearing loss and about 85% has obvious decline of speech detection rate.Part two Common hearing loss genetic screening in deaf-mute groups and analysis of causal gene in a Chinese hereditary hearing loss pedigree1. Study of GJB2、SLC26A4、12SrRNA genes pathogenic mutations in non-syndrome hearing loss patients in some district of Linyi in Shandong provinceTo analysis the carrying rate of common pathogenic loci in gene GJB2, SLC26A4, mitochondrial,12SrRNA in non-syndromic deafness patients in Linyi of Shandong province. We collected peripheral blood of 60 patients with non-syndromic sensorineural deafness. Genomic DNA was extracted from the blood. The mutation loci of GJB2, SLC26A4 IVS7-2A>G and 2168A>G,12SrRNA 1555A>G and 1494C>T were sequenced by restriction enzyme digestion and sequence analysis method after polymerase chain reaction (PCR) amplification. We found that 28 patients were pathogenic mutations carriers and 19 cases carry GJB2 (31.67%) among whom 17 cases carry double allele mutations.235delC mutation which was found in 15 cases is the most common mutation in gene GJB2. IVS7-2A>G in gene SLC26A4 was found in 4 cases containning 1 homozygous and 3 heterozygous mutations and 2 2168A>G heterozygous mutation was also found. 1555 A>G was found in 4 cases and no 1494>T was found in the group. One person carried both 235delC homozygous mutation and 1555 A>G mutation. The carrying rate of GJB2, SLC26A4 IVS7-2A>G and 2168A>G,12SrRNA 1555A>G and 1494C>T in non-syndromic deafness patients in the district of Liyi was consistent with the data in other districtes in China according to the published articles.2. Study of whole exome sequening in analysis of causal gene in a Chinese centenarian hereditary hearing loss pedigreeIn order to identify the causal gene in a small autosomal recessive hereditary hearing loss family pedigree. We extracted genomic DNA from the peripheral blood of two patients in the family. The whole exome sequening technology was used to detect the gene mutations of functional regions in the two cases. Then we excluded synonymous mutations, normal mutations in humans, functionally neutral gene mutation based on SIFT software. Also the mutations should accord with the genetic regularity of autosomal recessive heredity. Finally we obtained 42 candidate pathogenic genes for the family. Among them, the mutation locus in TMIE gene which has been known as deafness pathogenic gene was verified to be normal mutation by traditional sequencing technology. Our study excluded the known genetic mutation and select 41 gene for further study. The whole exome sequening technology is an effective method for less-patient autosomal recessive hereditary hearing loss family pedigree to identify causal gene.