Genome-wide Association Study for Noise-induced Cochlear Synaptopathy.

Article SummaryIn order to elucidate the genetic architecture of the auditory hair cell synapse and the susceptibility to noise-induced cochlear synaptopathy, we are providing the first genome-wide association study with 111 strains (n=695) of the Hybrid Mouse Diversity Panel based upon the strain variation of the wave 1 P1-N1 amplitude of the auditory brainstem responses both before and after noise exposure. Based on this association analysis and our cochlear gene expression data, we identified several novel loci and prioritized positional candidate genes related to cochlear synaptopathy, especially after exposure to noise.\n\nAbstractThis is the first genome-wide association study (GWAS) with the Hybrid Mouse Diversity Panel (HMDP) to define the genetic landscape of the auditory hair cell synapse and the susceptibility to noise-induced cochlear synaptopathy. We tested 5-week old female mice (n=695) from 111 HMDP strains (n= 6-7/strain) at baseline and post noise exposure using ABR wave 1 suprathreshold amplitudes (P1-N1 at 80 dB SPL) at 8, 12, 16, 24 and 32 kHz tone burst stimuli. Mice were exposed for 2 hours to 10 kHz octave band noise (OBN) at 108 dB SPL. A broad range of suprathreshold ABR wave 1 amplitude were detected across the HMDP strains. At the genome-wide significance threshold (-logP = 5.39), associations on Chr. 3 and Chr. 16 were identified at baseline. Also, association peaks on Chr. 2 and Chr. 13 were determined post noise exposure. In order to prioritize candidate genes, we generated gene expression microarray profiles using RNA isolated from cochleae in 64 HMDP strains (n =3 arrays per strain). We then used EMMA to perform an association analysis between all SNPs and array probes mapping within each region. A total of 17 genes (2 within Chr. 3 association, 6 within Chr. 2 association and 9 within Chr. 13 association) of these 3 loci were identified with at least 1 probe whose expression was regulated by a significant cis eQTL in the cochlea. Also, the genetic architecture of noise induced cochlear synaptopathy is distinct from that of baseline auditory nerve/synapse integrity. In summary, from this GWAS and our eQTL data, we identified 4 novel loci and prioritized positional candidate genes related to cochlear synaptopathy at baseline and after exposure to noise.