Systematic Screening of the Serotonin Receptor 1A (5-HT1A) Gene in Chronic Tinnitus

AbstractObjectiveChronic tinnitus is a highly prevalent condition and has been hypothesized to result from an innate disturbance in central nervous serotonergic transmission. Given the frequent comorbidity with major depression and anxiety, we argue that candidate genes for these disorders are likely to overlap. The present study addresses the gene encoding for the 5-HT1A receptor as a putative risk factor for tinnitus.MethodsIn 88 subjects with a diagnosis of chronic subjective tinnitus who underwent a detailed neurootological examination, the entire 5-HT1A gene was amplified using overlapping PCR products. Amplicons were custom sequenced bidirectionally and were screened for variants in multiple alignments against the human genome reference.ResultsWe identified a synonymous C>T exchange at residue 184 (Pro) in 7/88 subjects, but detected no missense variants in the population under study. Specifically, the following residues were fully conserved: 16 (Pro), 22(Gly), 28(Ile), 98 (Val), 220(Arg), 267 (Val), 273 (Gly), and 418 (Asn).DiscussionThe present data count against the causation of chronic tinnitus by a change in the 5-HT1A receptor’s amino acid sequence. However, the allele frequency for the 184Pro minor allele (0.04) reached twice the frequency reported in control cohorts from the same ethnicity. Additional investigations are invited to clarify the role of the 5-HT1A polymorphism in larger samples, and to control for comorbid affective disorders