Genetic Analysis of Age Related Hearing Impairment

年龄相关性听力障碍（ARHI，也称为老年性耳聋）损害了超过5亿人的感觉输入[1,2]，世界卫生组织预测，随着人口年龄中位数的稳步增长，对公共卫生的影响只会增加（http://www.who.int/en/）。许多研究表明，AHRI会对生活质量产生负面影响[2-5]。一项针对131535名加拿大人的横断面调查显示，听力受损的受试者患抑郁症的比例更高，而一项针对1140名老年人的研究则将听力缺陷与男性死亡风险的显著增加联系起来。ARHI的发病年龄差别很大；随着年龄的增长，总体患病率稳步上升，因此70%至80岁的人群中有60%表现出明显的听力障碍[8,9]。我们的团队最近完成了第一个全基因组关联研究（GWAS），确定了ARHI[10]的几个易感等位基因

Age-related hearing impairment (ARHI; also called presbycusis) impairs sensory input in more than a half of a billion people [1, 2], and the WHO predicts that the impact on public health will only increase as the median age of the population steadily increases (http://www.who.int/en/). A number of studies indicate that AHRI negatively impacts quality of life [2-5]. A cross-sectional survey of 131,535 Canadians reported that subjects with hearing impairment suffer higher rates of depression [6], while a study of 1140 elderly, linked hearing deficits with a significant increase in mortality risk in men [7]. The age of onset for ARHI varies markedly; with overall prevalence increasing steadily with age, so that 60% of individuals aged 70 to 80 demonstrate significant hearing impairment [8, 9]. Our team has recently completed the first genome-wide association study (GWAS) identifying several susceptibility alleles for ARHI [10] A major strength of this proposal lies in the group of investigators we have assembled. Each of the centers brings unique strengths and capabilities. The investigators from the House Ear Institute and the University of Antwerp have expertise in the genetics of hearing loss, GWAS and surgical access to cochlear tissue. Translational Genomics (TGen) has world-renowned expertise in genotyping and copy number variant (CNV) analysis. The success of this team is best illustrated by our discovery and publication of GRM7, the first susceptibility variant for ARHI found in a GWAS [10]. Leveraging these strengths uniquely positions us to dramatically advance our understanding of the underlying genetic architecture that predisposes humans to ARHI. Our LONG-TERM GOAL is to develop a comprehensive understanding of the specific genetic factors that contribute to ARHI. As an initial step towards that objective, we will build methodically upon results from our GWAS by analyzing a comprehensive human adult cochlear transcriptome that has been collected and sequenced by next generation sequencing (NGS). This cochlear transcriptome, and the existing transcriptome data in the mouse, will provide us with the opportunity to up weight genomic regions of association in our GWAS that contain genes expressed in the cochlea. This approach will enhance the power of our study providing a more cost-effective design. We propose the following SPECIFIC AIMS: AIM 1: Compile an accurate representation of the adult human cochlear transcriptome. Hypothesis: Genetic variants associated with ARHI reside within genes that are normally expressed in the cochlea. An in-depth characterization of the cochlear transcriptome has been initiated. The molecular biology has been completed and we are beginning the bioinformatics analysis. Several analytical methods exist that allow for weighting of individual SNPs due to biological criteria. We will use the new and existing cochlear gene list to a priori assign specific SNPs additional weight in the analysis of our Aim 2 data. AIM 2: Elucidate novel genes and biochemical networks associated with ARHI using a GWAS design. Hypothesis: ARHI is a complex disease resulting from allelic variation in multiple genes. We have recently confirmed the role of genetic variants in ARHI in a GWAS based on a pooling approach that demonstrated allelic association in several genes, including GRM7. Properly powered studies using hypothesis independent models of gene discovery have demonstrated great utility in identifying genomic variation associated with complex diseases. A stepwise approach, with up weighting of genomic regions containing genes expressed in the cochlea, and accounting for known covariant, further increases the power of our study, resulting in a cost-effective design. Our proposed investigation will not only improve our understanding of the genetic bases of ARHI, but will provide a rationale to pursue hypothesis-driven investigations that will in turn advance our understanding of the genetic, molecular, and cellular causes of ARHI. This improved knowledge base can be anticipated to constitute fertile ground for developing new evidence-based preventive and therapeutic approaches to treating ARHI.