USH1C encodes harmonin, a scaffolding protein essential for mechanotransduction in sensory organs. As a core component of the USH interactome, harmonin organizes a protein network with USH1G, CDH23, and MYO7A that mediates stereocilia development and maintenance in cochlear hair cells 1. In the retina, harmonin localizes to the periciliary region of photoreceptors and outer limiting membrane, where it maintains structural integrity and facilitates molecular trafficking between photoreceptor segments 2. Harmonin also functions as a central regulatory component of the intermicrovillar adhesion complex (IMAC), recruiting cadherins (CDHR2, CDHR5) and myosin 7B to stabilize microvilli in intestinal tuft cells and other epithelial tissues 3. Pathogenic USH1C mutations cause Usher syndrome type 1C, an autosomal recessive syndromic ciliopathy characterized by congenital sensorineural hearing loss and progressive retinitis pigmentosa 4. In genetic screening studies, USH1C mutations account for approximately 10-14.9% of USH1 cases 56. The diverse subcellular localization of harmonin isoforms in photoreceptors, Müller glia, and cone synapses correlates with the clinical phenotype in USH1C patients 2. Gene therapy delivery of harmonin_a1 transcript shows promise in reversing primary cilia defects in patient-derived cells, suggesting therapeutic potential for restoring inner ear and retinal function.