CEACAM16 is a tectorial membrane protein essential for normal auditory function. Primary function: CEACAM16 is a secreted glycoprotein component of the tectorial membrane (TM), the extracellular structure overlying the organ of Corti in the inner ear 1. Mechanism: CEACAM16 interacts with both α-tectorin (TECTA) and β-tectorin (TECTB) to stabilize their interactions and support development of the striated-sheet matrix within the TM 1. Loss of CEACAM16 results in reduced TECTB levels, absent Hensen's stripe formation, and altered cochlear mechanics, paradoxically enhancing otoacoustic emissions and causing spontaneous otoacoustic emissions in 70% of knockout mice 1. Disease relevance: Loss-of-function mutations in CEACAM16 cause postlingual progressive hearing loss through defective TM structure 2. Pathogenic variants include splice-altering mutations causing exon skipping and frameshift errors 2, missense mutations impairing protein secretion 3, and de novo mutations affecting conserved domains 4. Clinical significance: CEACAM16 mutations cause autosomal dominant nonsyndromic hearing loss DFNA4B 5 and autosomal recessive deafness 113 2. Affected individuals typically develop late-onset, high-frequency hearing loss beginning in childhood to early adulthood, progressing slowly with age 5.