Essential for proper differentiation of ectoderm. Acts synergistically with neurogenic locus proteins Notch and Delta during the separation of neural and epidermal cell lineages in response to the lateral inhibition signal. Voltage-insensitive monovalent cation channel. Ion transport is blocked by the presence of divalent cations. Detected in all tissues with neurogenic abilities, for example the neurogenic ectoderm. Aquaporins contain two tandem repeats each containing three membrane-spanning domains and a pore-forming loop with the signature motif Asn-Pro-Ala (NPA). Phosphorylated at its C-terminus. Separation of neuroblasts from the ectoderm into the inner part of embryo is one of the first steps of CNS development in insects, this process is under control of the neurogenic genes. Mutation in bib gene underlies 'big brain' development defect. Belongs to the MIP/aquaporin (TC 1.A.8) family.