It is the molecular structure to which AVP binds and gives the message to begin the urine concentrating process. Normally, the V2 receptor binds with AVP and accepts its message. This lets a lot more water than usual flow through these kidney cells, an event essential for urine concentration. Genes synthesize proteins , but when a gene is mutated , it can produce faulty proteins that range from partially to completely non-functional and therefore can produce some functional disorder . The genes that produce AVPR2 and AQP2 are called the AVPR2 gene and the AQP2 gene.
Mutations can occur at different locations on genes.
For example, two people can have CNDI caused by mutations of their AVPR2 gene, yet the mutation in one can be located at one end of the gene, whereas the location of the other can be at the other end. Vargas-Poussou, et al., studied 14 CNDI patients belonging to 12 unrelated families of diverse ethnic origin. They found ten of the patients had mutations in their AVPR2 genes. Six of the mutations had been found in the same locations as in other CNDI patients, but four had not. In an AQP2 mutation, the AVPR2 binds with AVP and the process begins, but the AQP2s do not travel to the cell membranes to make them more water permeable .