Loxhd1, encoding lipoxygenase homology domain 1, is crucial for the mechanotransduction process in cochlear hair cells. It consists of 15 polycystin lipoxygenase α -toxin (PLAT) repeats, which can bind lipids and proteins. LOXHD1 is distributed along the stereocilia length and is involved in the auditory mechanotransduction pathway, essential for normal hearing function [2].

Two LOXHD1 mouse models with mutations in the 10th PLAT repeat showed mechanotransduction defects. Although mechanotransduction currents in mutant inner hair cells were similar to wild-type in the first postnatal week, they were severely affected by postnatal day 11. This phenotype onset correlated with the postnatal LOXHD1 expression/localization in the hair bundle. The defect was not due to hair bundle morphological changes or tip-link number reduction. Immunolocalization showed that two proteins of the tip-link complexes were maintained in mutants, suggesting the mechanotransduction machinery was present but not activatable [2]. Additionally, mouse models demonstrated that LOXHD1 is essential for keeping TMC1-pore forming subunits at the tip link, which is crucial for the function of mature auditory channels. In LOXHD1's absence, TMC1 mislocalizes away from the force transmission site [3,4].

In conclusion, Loxhd1 is indispensable for hair-cell mechanotransduction and normal hearing function. Studies using mouse models have revealed its role in maintaining the proper localization of key components in the auditory mechanotransduction complex. Mutations in Loxhd1 are associated with non-syndromic sensorineural hearing loss (NSHL), including DFNB77, auditory neuropathy spectrum disorder, and down-sloping hearing loss, highlighting its significance in understanding genetic-related hearing impairments [1,2,3,4,5,6].

References:

1. Yu, Sha, Chen, Wen-Xia, Zhang, Yun-Fei, Wang, Huijun, Xu, Zheng-Min. 2021. Recessive LOXHD1 variants cause a prelingual down-sloping hearing loss: genotype-phenotype correlation and three additional children with novel variants. In International journal of pediatric otorhinolaryngology, 145, 110715. doi:10.1016/j.ijporl.2021.110715. https://pubmed.ncbi.nlm.nih.gov/33892339/

2. Trouillet, Alix, Miller, Katharine K, George, Shefin Sam, Ricci, Anthony, Grillet, Nicolas. 2021. Loxhd1 Mutations Cause Mechanotransduction Defects in Cochlear Hair Cells. In The Journal of neuroscience : the official journal of the Society for Neuroscience, 41, 3331-3343. doi:10.1523/JNEUROSCI.0975-20.2021. https://pubmed.ncbi.nlm.nih.gov/33707295/

3. Wang, Pei, Miller, Katharine K, He, Enqi, Cunningham, Christopher L, Grillet, Nicolas. 2024. LOXHD1 is indispensable for maintaining TMC1 auditory mechanosensitive channels at the site of force transmission. In Nature communications, 15, 7865. doi:10.1038/s41467-024-51850-4. https://pubmed.ncbi.nlm.nih.gov/39256406/

4. Wang, Pei, Miller, Katharine K, He, Enqi, Cunningham, Christopher L, Grillet, Nicolas. 2024. LOXHD1 is indispensable for coupling auditory mechanosensitive channels to the site of force transmission. In Research square, , . doi:10.21203/rs.3.rs-3752492/v1. https://pubmed.ncbi.nlm.nih.gov/38260480/

5. Morlet, T, Robbins, K M, Stabley, D, Sol-Church, K, O'Reilly, R C. 2021. Mutations in LOXHD1 gene can cause auditory neuropathy spectrum disorder. In Otolaryngology case reports, 21, . doi:10.1016/j.xocr.2021.100367. https://pubmed.ncbi.nlm.nih.gov/35875410/

6. Kim, Bong Jik, Jeon, Hyoung Won, Jeon, Woosung, Oh, Doo-Yi, Choi, Byung Yoon. 2021. Rising of LOXHD1 as a signature causative gene of down-sloping hearing loss in people in their teens and 20s. In Journal of medical genetics, 59, 470-480. doi:10.1136/jmedgenet-2020-107594. https://pubmed.ncbi.nlm.nih.gov/33753533/