MORN4 (MORN repeat containing 4) functions as a protein-binding adaptor that regulates myosin III motor proteins through its β-hairpin-based tandem repeats. Structurally, MORN4 forms an extended single-layered β-sheet with a U-shaped groove that binds with high affinity and specificity to the tail cargo-binding region of myosin IIIA (MYO3A) 1. This interaction is conserved across species, with MORN4 serving as the vertebrate ortholog of Drosophila Retinophilin 2. In cellular localization, MORN4 and MYO3A co-localize to actin-rich filopodia tips in a motor-dependent manner, where MYO3A transports MORN4 distally while MORN4 enhances motor localization by tethering it to the plasma membrane 2. Functionally, MORN4 participates in hair bundle morphogenesis within auditory hair cells, where it contributes to limiting stereocilia and microvilli elongation during development 3. Based on GO annotations and UniProt data, MORN4 likely promotes axonal degeneration following neuronal injury, though direct mechanistic evidence in disease contexts is lacking from the provided abstracts. The precise role in injury-induced degeneration warrants further investigation.