COCH encodes cochlin, a protein with critical roles in inner ear homeostasis and structural integrity. Cochlin is abundantly expressed in the spiral ligament and spiral limbus of the inner ear 1, where it functions in sensory perception of sound and regulation of cell shape. The protein binds to collagen and interacts with the extracellular matrix [based on GO annotations], contributing to structural support in auditory tissues. Pathogenic variants in COCH cause DeafNess Autosomal Dominant 9 (DFNA9), a progressive sensorineural hearing loss typically onset around age 32.8 years with annual deterioration of approximately 3 dB HL per year 2. The Pro51Ser (P51S) mutation represents a well-characterized variant associated with profound hearing loss by age 76 and concurrent vestibular dysfunction beginning around age 34 2. DFNA9 pathology involves impaired intracellular trafficking of cochlin, resulting in widespread accumulation of acellular eosinophilic deposits throughout the inner ear labyrinth 1. This cellular dysfunction disrupts normal auditory and vestibular signaling. COCH variants are also associated with autosomal recessive deafness (Deafness DFNB110), indicating both dominant and recessive inheritance patterns. Single-cell transcriptomics identified COCH+ fibroblasts as a novel cell population in human tissues 3, suggesting broader roles beyond the inner ear. Understanding COCH pathogenesis is essential for developing therapeutics targeting hereditary hearing loss.