A humanized murine model, demonstrating dominant progressive hearing loss caused by a novel KCNQ4 mutation (p.G228D) from a large Chinese family

Natural History of KCNQ4 p.G285S Related Hearing Loss, Construction of iPSC and Mouse Model

OBJECTIVE

KCNQ4 is one of the most common disease-causing genes involved in autosomal dominant non-syndromic hearing loss. We previously found that patients with KCNQ4 p.G285S exhibited a much more rapid deterioration in hearing loss than those with other KCNQ4 variants. To determine the rate of hearing loss and assess the disease for further analysis, we performed a long-term follow-up of these patients and generated patient-derived induced pluripotent stem cells (iPSCs), and a mouse model.

METHODS

Patients with KCNQ4 p.G285S from a five-generation family with hearing loss were followed up from 2005 to 2022. iPSCs were generated by stimulating peripheral blood mononuclear cells from the proband, and their pluripotency was determined. The Kcnq4 p.G286S mouse model was generated using CRISPR/Cas9, and its genotype and phenotype were identified.

RESULTS

(1) The annual rates of hearing loss at the frequencies of speech were 0.96 dB for the proband and 0.87 dB for his father during the follow-up period, which were faster than patients with other KCNQ4 variants. (2) The patient-derived iPSC line carrying KCNQ4 p.G285S, possessed the capacity of differentiation and pluripotency capacities. (3) Mutant mice with Kcnq4 p.G286S exhibited hearing loss and outer hair cell loss at 1 month of age.

CONCLUSION

Patients with KCNQ4 p.G285S variant exhibited significantly accelerated progression of hearing loss compared to those with other reported variants. Awareness of the natural history of hearing loss associated with KCNQ4 p.G285S is beneficial for genetic counseling and prognosis. The generation of the iPSCs and mouse model can provide a valuable foundation for further in-depth analyses.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:2356-2363, 2024.

The applications of CRISPR/Cas-mediated genome editing in genetic hearing loss

Hearing loss (HL) can be caused by a number of different genetic factors. Non-syndromic HL refers that HL occurs as an isolated symptom in an individual, whereas syndromic HL refers that HL is associated with other symptoms or abnormalities. To date, more than 140 genes have been identified as being associated with non-syndromic HL, and approximately 400 genetic syndromes can include HL as one of the clinical symptoms. However, no gene therapeutic approaches are currently available to restore or improve hearing. Therefore, there is an urgent necessity to elucidate the possible pathogenesis of specific mutations in HL-associated genes and to investigate the promising therapeutic strategies for genetic HL. The development of the CRISPR/Cas system has revolutionized the field of genome engineering, which has become an efficacious and cost-effective tool to foster genetic HL research. Moreover, several in vivo studies have demonstrated the therapeutic efficacy of the CRISPR/Cas-mediated treatments for specific genetic HL. In this review, we briefly introduce the progress in CRISPR/Cas technique as well as the understanding of genetic HL, and then we detail the recent achievements of CRISPR/Cas technique in disease modeling and therapeutic strategies for genetic HL. Furthermore, we discuss the challenges for the application of CRISPR/Cas technique in future clinical treatments.

Precise detection of CRISPR-Cas9 editing in hair cells in the treatment of autosomal dominant hearing loss

Gene therapy would benefit from the effective editing of targeted cells with CRISPR-Cas9 tools. However, it is difficult to precisely assess the editing performance in vivo because the tissues contain many non-targeted cells, which is one of the major barriers to clinical translation. Here, in the Atoh1-GFP;Kcnq4 ^+/G229D mice, recapitulating a novel mutation we identified in a hereditary hearing loss pedigree, the high-efficiency editing of CRISPR-Cas9 in hair cells (34.10% on average) was precisely detected by sorting out labeled cells compared with only 1.45% efficiency in the whole cochlear tissue. After injection of the developed AAV_SaCas9-KKH_sgRNA agents, the Kcnq4 ^+/G229D mice showed significantly lower auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) thresholds, shorter ABR wave I latencies, higher ABR wave I amplitudes, increased number of surviving outer hair cells (OHCs), and more hyperpolarized resting membrane potentials of OHCs. These findings provide an innovative approach to accurately assess the underestimated editing efficiency of CRISPR-Cas9 in vivo and offer a promising strategy for the treatment of KCNQ4-related deafness.