Grxcr1, or glutaredoxin cysteine-rich 1, is crucial for the morphogenesis of stereocilia in cochlear hair cells, with its mutations linked to non-syndromic sensorineural deafness in humans [3,5,6,7]. It may also play a role in the growth and development of feathers, muscles, and bones in geese [8].

In mouse models, Grxcr1-deficient hair cells have very thin stereocilia with less F-actin content. GRXCR1 is diffusely distributed throughout the stereocilia and interacts with GRXCR2. Reducing taperin expression level does not rescue the morphological defects of stereocilia or hearing loss in Grxcr1-deficient mice, indicating different functions from GRXCR2 [1]. In Tasmanian devil (tde) mice, a disrupted Grxcr1 gene leads to disorganized hair bundles, abnormally thin stereocilia, and reduced mechanoelectrical transducer (MET) current, suggesting GRXCR1 is key for normal stereociliary bundle growth prior to hearing onset [2]. Zebrafish grxcr1 mutants also show thinner hair bundles, and Grxcr1 regulates mechanoreceptor development by preventing the interaction between Ush1c and Ush1ga proteins [4]. In pirouette mice, loss of Grxcr1 function results in abnormally thin and slightly shortened stereocilia, and overexpression of GRXCR1 in transfected cells affects actin-filament-rich structures [5].

In conclusion, Grxcr1 is essential for the normal development of hair bundle stereocilia and mechanoelectrical transduction in cochlear hair cells. Mouse and zebrafish models have revealed its role in modulating actin cytoskeletal architecture during stereocilia development, contributing to our understanding of non-syndromic sensorineural deafness [1,2,4,5].

References:

1. Liu, Chang, Zhao, Bo. 2021. Murine GRXCR1 Has a Different Function Than GRXCR2 in the Morphogenesis of Stereocilia. In Frontiers in cellular neuroscience, 15, 714070. doi:10.3389/fncel.2021.714070. https://pubmed.ncbi.nlm.nih.gov/34366792/

2. Lorente-Cánovas, Beatriz, Eckrich, Stephanie, Lewis, Morag A, Marcotti, Walter, Steel, Karen P. 2022. Grxcr1 regulates hair bundle morphogenesis and is required for normal mechanoelectrical transduction in mouse cochlear hair cells. In PloS one, 17, e0261530. doi:10.1371/journal.pone.0261530. https://pubmed.ncbi.nlm.nih.gov/35235570/

3. Rastad, Hadith, Samimisedeh, Parham, Savad, Shahram, Seifi Alan, Mahnaz. 2023. A Novel Exon 2 Deletion Mutation in the GRXCR1 Gene Associated With Non-Syndromic Hearing Loss: A Case Report and Review of Literatures. In The Annals of otology, rhinology, and laryngology, 132, 1493-1495. doi:10.1177/00034894231161866. https://pubmed.ncbi.nlm.nih.gov/37009772/

4. Blanco-Sánchez, Bernardo, Clément, Aurélie, Fierro, Javier, Washbourne, Philip, Westerfield, Monte. . Grxcr1 Promotes Hair Bundle Development by Destabilizing the Physical Interaction between Harmonin and Sans Usher Syndrome Proteins. In Cell reports, 25, 1281-1291.e4. doi:10.1016/j.celrep.2018.10.005. https://pubmed.ncbi.nlm.nih.gov/30380418/

5. Odeh, Hana, Hunker, Kristina L, Belyantseva, Inna A, Smith, Richard J H, Kohrman, David C. 2010. Mutations in Grxcr1 are the basis for inner ear dysfunction in the pirouette mouse. In American journal of human genetics, 86, 148-60. doi:10.1016/j.ajhg.2010.01.016. https://pubmed.ncbi.nlm.nih.gov/20137774/

6. Mori, Kentaro, Miyanohara, Ikuyo, Moteki, Hideaki, Kurono, Yuichi, Usami, Shin-Ichi. 2015. Novel mutation in GRXCR1 at DFNB25 lead to progressive hearing loss and dizziness. In The Annals of otology, rhinology, and laryngology, 124 Suppl 1, 129S-34S. doi:10.1177/0003489415575061. https://pubmed.ncbi.nlm.nih.gov/25802247/

7. Schraders, Margit, Lee, Kwanghyuk, Oostrik, Jaap, Leal, Suzanne M, Kremer, Hannie. 2010. Homozygosity mapping reveals mutations of GRXCR1 as a cause of autosomal-recessive nonsyndromic hearing impairment. In American journal of human genetics, 86, 138-47. doi:10.1016/j.ajhg.2009.12.017. https://pubmed.ncbi.nlm.nih.gov/20137778/

8. Ouyang, J, Wu, Y, Li, Y, Yan, X, Chen, H. 2022. Identification of key candidate genes for wing length-related traits by whole-genome resequencing in 772 geese. In British poultry science, 63, 747-753. doi:10.1080/00071668.2022.2102889. https://pubmed.ncbi.nlm.nih.gov/35848598/