Identification of human GJB2 35delG modifying genes using induced pluripotent stem cells

• Applicant: Professor Dr. Joerg Waldhaus, Ph.D.
• Subject Area: Otolaryngology, Phoniatrics and Audiology ; Human Genetics ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2013 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 240351029

Approximately 1 in 3,000 babies born suffers from the most common form of hereditary hearing loss called DFNB1, which is caused by mutations in the GJB2 gene. The degree of hearing loss varies substantially among different patients with the vast majority having severe hearing loss but a small subset of patients displays only a mild form of hearing loss. There is a need for developing future treatments that ameliorate DFNB1 deafness in newborn children because it would allow these children to naturally acquire spoken language skills and in the long run, it could make cochlear implantation obsolete.My research aim is to identify the molecular reasons why patients that carry exactly the same mutation in the GJB2 gene (35delG) end up with different levels of hearing loss. I speculate that there might be other genetic factors involved that modulate the impact of the known DFNB1 mutation on the ability to hear sound. To achieve this goal, I will apply patient specific induced stem cell (iPSC)-based technology that helps me to answer my questions, which would not be possible to be addressed in any animal model due to the complexity of the disease. I will start with a blood sample from a patient and by applying different reprogramming factors, I will be able to generate a stem cell population that is capable of differentiating into sensory hair- and supporting cell types from the inner ear. Using this technique will enable me for the first time to transfer the DFNB1 phenotype to the culture dish and to characterize the inner ear cells physiologically in comparison with cells from normal hearing individuals. To identify the factors modifying the severity of the phenotype, I will apply a whole transcriptome deep sequencing approach analyzing the in vitro generated cell types to identify variations in transcribed genes. I propose obtaining statistical validation of identified variations by conducting a genome wide association study with DFNB1 patients that belong to the severely and mildly affected groups. Further validation of the candidates will be done by gain and loss of function experiments while monitoring for physiological performance in patient-derived cells.Insight into genetic modifiers of DFNB1 is a pre-requisite to the development of novel treatment strategies for severely affected children, which at some point might help them to live normal lives.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Stefan Heller, Ph.D.