Identification of novel variants in the TMIE gene of patients with nonsyndromic hearing loss

Objective: To determine whether variants of the TMIE gene are causes of nonsyndromic deafness in Taiwan. Methods: A genetic survey was made from 370 individuals, with 250 nonsyndromic hearing loss and 120 normal hearing individuals. Genomic DNA was extracted from peripheral blood leukocytes and then subjected to PCR to amplify selected exons and flanking introns of the TMIE gene; the amplified products were screened for base variants by autosequence. Data from the two groups were then compared using Fisher's two-tailed exact test and Armitage's trend test. Results: The analysis revealed 7 novel variants in the TMIE gene. Of the 7 variants, 5 variants were found in both nonsyndromic hearing loss and normal hearing group. Both allelic and genotype frequencies of these sequence changes did not differ significantly between patients and controls (P>0.05). However, a missense variant (c.257G >A) and one promoter variant (g.1-219A >T) were found in two patients with nonsyndromic hearing loss. Family study and microsatellite analysis found that c.257G >A variant is not inherited from his parents. The c.257G >A variant encodes a protein with glutamine at position 86 instead of arginine (p.R86Q), a residue that is conserved in mammals but different in fish, and predicted to be extracellular. Conclusions: Despite the fact that the frequency of TMIE variants in our study subjects was low, we suggested that c.257G >A (p.R86Q) variant is a de novo and may be as a risk factor for the development of hearing loss in Taiwanese.