Assignment of the Human Gene for the Water Channel of Renal Collecting Duct Aquaporin 2 (AQP2) to Chromosome 12 Region q12-->q13

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Title: Assignment of the Human Gene for the Water Channel of Renal Collecting Duct Aquaporin 2 (AQP2) to Chromosome 12 Region q12-->q13
Authors: Deen, Peter M.T.; Weghuis, D.O.; Sinke, R.J.; Geurts van Kessel, A.; Wieringa, Be; van Os, Carel
Publisher: Cytogenetics and Cell Genetics
Date Published: 1994
Reference Number: 295
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The chromosomal localization of the gene encoding aquaporin 2 (previously called WCH-CD), which acts as a water channel in the collecting tubules of the kidney, was determined. Southern blot hybridizations of chromosomal DNA from a panel of 25 different human-rodent hybrid cell lines assigned AQP2 to the q-arm of human chromosome 12. Additionally, in situ hybridization on R-banded metaphase chromosomes localized AQP2 to the q12-->q13 region of this chromosome.

This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)

The kidney plays a primary role in the maintenance of water balance by filtering body water and reabsorbing it back into the body. Ninety percent of the body water flowing through the nephrons (the main working unit of the kidney) is reabsorbed in the sections of the kidney called the proximal tubule and the descending limb of Henle. The remaining 10% is reabsorbed in a section of the kidney called the collecting tubules.

The disorder, nephrogenic diabetes insipidus (NDI) is characterized by the kidney's inability to respond to the antidiuretic hormone, arginine vasopressin (AVP). Because it does not respond to AVP, the kidney is unable to concentrate urine by reabsorbing the body water flowing through the kidney collecting duct. As a result, the NDI patient experiences polyuria (chronic passage of large volumes of urine) and polydipsia (chronic, excessive thirst).

NDI may either be acquired or inherited. The inherited forms of NDI may be either inherited in an X-linked recessive or an autosomal recessive pattern. This indicates that there are two different genes that, when mutated, cause NDI: one that is located on the X chromosome, and one that is located on one of the 22 autosomal (non-sex) chromosomes.

The gene responsible for X-linked NDI is the vasopressin-2 (V2R) gene. The gene researchers suspect is responsible for the autosomal recessive form is the aquaporin-2 (AQP2) gene, which codes for a water channel in the collecting duct that is regulated by AVP. But before this can be confirmed researchers must determine whether the AQP2 gene is located on one of the 22 autosomal chromosomes and, if yes, at which specific location.

Deen, et al., analyzed the hybridizations of chromosomal DNA from a panel of 25 different human-mouse hybrid cell lines and found the AQP2 gene was located on chromosome 12. Additionally, in situ hybridization of the AQP2 gene with human chromosomes, showed that the AQP2 gene was located in region q12-q13 on chromosome 12. Therefore, mutations in the human AQP2 gene could be responsible for the autosomal recessive form of NDI.