The function of MIP (major intrinsic protein of lens fiber, Ensembl gene identifier ENSG00000135517) is as follows. Aquaporins form homotetrameric transmembrane channels, with each monomer independently mediating water transport across the plasma membrane along its osmotic gradient (PubMed:11001937, PubMed:24120416). Specifically expressed in lens fiber cells, this aquaporin is crucial for maintaining lens water homeostasis and transparency. Beyond water permeability, it also acts as a cell-to-cell adhesion molecule, forming thin junctions between lens fiber cells that are essential for maintaining the ordered structure and transparency of the lens (PubMed:24120416). {ECO:0000269|PubMed:11001937, ECO:0000269|PubMed:24120416}.