Generation of marmoset monkeys with a non-mosaic disruption of the OTOF gene as a model of human deafness.

Disabling hearing impairment is a common human sensory deficit. OTOF is a major deafness gene. It codes for the synaptic protein otoferlin and is essential for transmitter release by inner hair cells (IHCs). Upon genetic loss of otoferlin, cochlear structure and function remain intact up to the IHC synapses, which fail to encode sound. Building on preclinical hearing restoration by AAV-mediated cochlear gene transfer in mice, clinical OTOF-gene-therapy trials are now targeting the pediatric population. However, preclinical optimization and characterization remain urgent needs for the development of OTOF-gene-therapy. Here, we report on the generation and characterization of a marmoset KO that models OTOF-related auditory synaptopathy and can thus address these needs. Following ovary stimulation, harvesting, in vitro maturation and fertilization of oocytes, we injected the zygotes with Cas9 and guide RNAs to disrupt OTOF. Mutant embryos were transferred into the uterus of foster mothers. Marmosets with biallelic, non-mosaic OTOF-KO were normally born and raised by their respective foster parents. Auditory brainstem recordings and otoacoustic emissions revealed profound auditory synaptopathy and OTOF-KO was further validated by the lack of otoferlin expression in IHCs. The new non-human primate model of OTOF-related auditory synaptopathy will serve studies of specificity, efficacy, and longevity of novel inner ear therapies.