Gene therapy for hearing loss

• Applicant: Professorin Dr. Ellen Reisinger
• Subject Area: Otolaryngology, Phoniatrics and Audiology ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 416116807

• Final Report Year: 2024

Final Report Abstract

Gene therapy for hearing loss or deafness has recently been clinically tested for the first time. Patients with profound sensorineural deafness type DFNB9, which is caused by mutations in the OTOF gene, were treated with therapeutic viral vectors and can hear now. For this breakthrough, a so-called “dual-AAV”-strategy for gene therapy was applied, which, for OTOF, was previously developed in my lab. Hearing measurements in these treated patients show that the hearing thresholds are in the range of moderate hearing loss, so that an improvement of the gene therapy still appears necessary, which is in the focus of this project. First, we were able to further characterize otoferlin function and DFNB9 deafness. We found that the maturation of synapses in inner hair cells is partially altered in the absence of otoferlin, and that inner and outer hair cells die over time, the latter of which is accelerated by noise. By characterizing two new mouse lines and by pharmacological manipulation, we found out how the involvement of otoferlin in endocytosis is regulated. For the further development of gene therapy, we established the production and purification of adeno-associated viruses (AAVs) in the laboratory, as well as a specially optimized in vitro organotypic cultures for AAV transduction tests. The conversion of the inner ear injection to a less invasive method is almost complete. For a more comprehensive and precise analysis of transduction in the inner ear and for cell counts we succeeded in developing a reliable protocol for clearing inner ears, which makes them transparent and accessible for light sheet microscopy.

Publications

• PKCα-dependent interaction of otoferlin and calbindin: evidence for regulation of endocytosis in inner hair cells.
  Cepeda, Andreia P.; Al-Moyed, Hanan; Lenz, Christof; Urlaub, Henning & Reisinger, Ellen
  
• Dual-AAV delivery of large gene sequences to the inner ear. Hearing Research, 394, 107857.
  Reisinger, Ellen
  
• The Many Faces of DFNB9: Relating OTOF Variants to Hearing Impairment. Genes, 11(12), 1411.
  Vona, Barbara; Rad, Aboulfazl & Reisinger, Ellen
  
• HNO-Kongress Innsbruck: Gentherapie der Taubheit IEB in Triest 2022, invited target lecture: Auditory Neuropathy – from basic research to personalized medicine
  E. Reisinger
  
• Otoferlin Is Required for Proper Synapse Maturation and for Maintenance of Inner and Outer Hair Cells in Mouse Models for DFNB9. Frontiers in Cellular Neuroscience, 15.
  Stalmann, Ursula; Franke, Albert Justin; Al-Moyed, Hanan; Strenzke, Nicola & Reisinger, Ellen
  
• MBHD in Iowa: A Dual-AAV Approach with Human Otoferlin cDNA Rescues Hearing in Otof-/- Mice for at Least 10 Months
  E. Reisinger
  
• MBHD in Iowa: A Novel Mutation in the FerA Domain of Otoferlin Causes Age- Related Hearing Impairment
  X. Smyrnakou
  
• ARO in Orlando: A Novel Mutation in the FerA Domain of Otoferlin Causes Age-Dependent Progressive Hearing Impairment
  I. Bahader & X. Smyrnakou
  
• ARO in Orlando: The Effects of Noise Trauma on Outer Hair Cell Function of Otoferlin Knock-Out Mice
  F. Becker
  
• IEB in London: PKCα-dependent interaction of otoferlin with calbindin or myosin VI modulates inner hair cell physiology
  A. Deutschmann