Altered Fhod3 expression involved in progressive high-frequency hearing loss via dysregulation of actin polymerization stoichiometry in the cuticular plate

• Published in: PLoS genetics Vol. 20; no. 3; p. e1011211
• Main Authors: Boussaty, Ely Cheikh, Ninoyu, Yuzuru, Andrade, Leonardo R, Li, Qingzhong, Takeya, Ryu, Sumimoto, Hideki, Ohyama, Takahiro, Wahlin, Karl J, Manor, Uri, Friedman, Rick A
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 18.03.2024; Public Library of Science (PLoS)
• Subjects: Actin; Actins - genetics; Actins - metabolism; Age; Animals; Biology and Life Sciences; Chromosome 18; Cochlea; Cochlea - metabolism; Ears & hearing; Engineering and Technology; Formins - genetics; Gene expression; Gene loci; Genetic aspects; Genome-wide association studies; Genome-Wide Association Study; Genomes; Genomic analysis; Genomics; Hair cells; Health aspects; Hearing; Hearing loss; Hearing Loss, High-Frequency; Hearing protection; Homology; Investigations; Localization; Math1 protein; Medicine and Health Sciences; Mice; Mice, Knockout; Microscopy; Muscle proteins; Older people; Outer hair cells; Pax2 protein; Phalloidin; Phenotypes; Polymerization; Proteins; Research and Analysis Methods; Scientific equipment and supplies industry; Somatotropin; Stoichiometry; Structure-function relationships; United States; Germany
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1011211

Age-related hearing loss (ARHL) is a common sensory impairment with complex underlying mechanisms. In our previous study, we performed a meta-analysis of genome-wide association studies (GWAS) in mice and identified a novel locus on chromosome 18 associated with ARHL specifically linked to a 32 kHz tone burst stimulus. Consequently, we investigated the role of Formin Homology 2 Domain Containing 3 (Fhod3), a newly discovered candidate gene for ARHL based on the GWAS results. We observed Fhod3 expression in auditory hair cells (HCs) primarily localized at the cuticular plate (CP). To understand the functional implications of Fhod3 in the cochlea, we generated Fhod3 overexpression mice (Pax2-Cre+/-; Fhod3Tg/+) (TG) and HC-specific conditional knockout mice (Atoh1-Cre+/-; Fhod3fl/fl) (KO). Audiological assessments in TG mice demonstrated progressive high-frequency hearing loss, characterized by predominant loss of outer hair cells, and a decreased phalloidin intensities of CP. Ultrastructural analysis revealed loss of the shortest row of stereocilia in the basal turn of the cochlea, and alterations in the cuticular plate surrounding stereocilia rootlets. Importantly, the hearing and HC phenotype in TG mice phenocopied that of the KO mice. These findings suggest that balanced expression of Fhod3 is critical for proper CP and stereocilia structure and function. Further investigation of Fhod3 related hearing impairment mechanisms may lend new insight towards the myriad mechanisms underlying ARHL, which in turn could facilitate the development of therapeutic strategies for ARHL.