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Original Investigation
September 2016

Association of TMTC2 With Human Nonsyndromic Sensorineural Hearing Loss

Author Affiliations
  • 1Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, Milwaukee
  • 2Department of Biology, Boston College, Chestnut Hill, Massachusetts
  • 3Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee
  • 4Department of Genetics, Texas Biomedical Research Institute, San Antonio
  • 5Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee
  • 6Max Delbrück Center for Molecular Medicine, Berlin-Buch, Germany
  • 7Department of Human Genetics, University of Utah School of Medicine, Salt Lake City
  • 8Department of Anesthesiology, Medical College of Wisconsin, Milwaukee
JAMA Otolaryngol Head Neck Surg. 2016;142(9):866-872. doi:10.1001/jamaoto.2016.1444

Importance  Sensorineural hearing loss (SNHL) is commonly caused by conditions that affect cochlear structures or the auditory nerve, and the genes identified as causing SNHL to date only explain a fraction of the overall genetic risk for this debilitating disorder. It is likely that other genes and mutations also cause SNHL.

Objective  To identify a candidate gene that causes bilateral, symmetric, progressive SNHL in a large multigeneration family of Northern European descent.

Design, Setting, and Participants  In this prospective genotype and phenotype study performed from January 1, 2006, through April 1, 2016, a 6-generation family of Northern European descent with 19 individuals having reported early-onset hearing loss suggestive of an autosomal dominant inheritance were studied at a tertiary academic medical center. In addition, 179 unrelated adult individuals with SNHL and 186 adult individuals reporting nondeafness were examined.

Main Outcomes and Measures  Sensorineural hearing loss.

Results  Nine family members (5 women [55.6%]) provided clinical audiometric and medical records that documented hearing loss. The hearing loss is characterized as bilateral, symmetric, progressive SNHL that reached severe to profound loss in childhood. Audiometric configurations demonstrated a characteristic dip at 1000 to 2000 Hz. All affected family members wear hearing aids or have undergone cochlear implantation. Exome sequencing and linkage and association analyses identified a fully penetrant sequence variant (rs35725509) on chromosome 12q21 (logarithm of odds, 3.3) in the TMTC2 gene region that segregates with SNHL in this family. This gene explains the SNHL occurrence in this family. The variant is also associated with SNHL in a cohort of 363 unrelated individuals (179 patients with confirmed SNHL and 184 controls, P = 7 × 10−4).

Conclusions and Relevance  A previously uncharacterized gene, TMTC2, has been identified as a candidate for causing progressive SNHL in humans. This finding identifies a novel locus that causes autosomal dominant SNHL and therefore a more detailed understanding of the genetic basis of SNHL. Because TMTC2 has not been previously reported to regulate auditory function, the discovery reveals a potentially new, uncharacterized mechanism of hearing loss.