Monday, July 30, 2007

Aquaporin: Water side niche induced?

Dive Physiology: Aquaporin duplication in human genome

[I'd appreciate any comments on whether AQP7 may have duplicated in the human genome (selected for in our ancestors) because of daily diving (breath hold O2 conservation) giving a survival advantage. The article focuses on endurance running on savannas, but I think diving played a larger part in the genetic selection for Aquaporin. Savanna chimps were not selected for aquaporin duplication any more than chimps which live in the deepest tropical rainforest, and savanna baboons were not selected for more aquaporin than rainforest monkeys, so savanna living does not equal higher aquaporin duplication.

However, more efficient energy production while underwater is valuable to a breath-hold diver, for better endurance underwater (while surrounded by abundant water supplies) and extra fat stores is not detrimental to a diver (it insulates the body core aka "bioprene") but may be detrimental for a distance runner. See the Kenyan marathon runners and San Bushmen persistence hunters in the Kalahari desert, generally very skinny, almost no fat reserves, amidst scarce water resources.]

An analysis of DNA from 10 primate species reveals that, compared with the genome of chimpanzees and gorillas, our genome includes many more duplicates of a gene called aquaporin 7 (AQP7), which transports water and sugary compounds into cells. Humans appear to have five copies of this gene, whereas chimps have just two, and other primates carry only one copy.

Humans are believed to possess anywhere from 20,000 to 25,000 different genes. But in some cases, we carry multiple copies of the same gene. And the more duplicates of a gene that exist within a cell, the more protein from the gene that gets produced, according to James Sikela at the University of Colorado Health Sciences Center in Aurora, Colorado, US.

Given the potential influence exerted by extra gene copies, Sikela and his colleagues wondered how humans might differ from other primate species in terms of the number of duplicates we carry. The team extracted DNA from blood samples taken from various primates including humans...

The researchers calculated how many copies of various genes each species carries with the help of DNA "micro-array" technology. If large quantities of the DNA from a given genome attached to certain parts of the micro-array chip, this indicated that it contained multiple copies of a specific gene.

After using this method to screen more than 20,000 genes, Sikela and his colleagues found 84 genes for which the copy number in the human genome differs from that of other primates.

The aquaporin AQP7 gene in particular caught their attention. The protein made by the gene functions as an important channel in the cell membrane. Specifically, the channel allows water and a sugary compound called glycerol to enter the cell, where they are used to produce energy. This has the potential to make a difference in long bouts of exercise, when the body needs to mobilise energy molecules from fat stores.

Separate article on aquaporin family, re: kidneys, testes, fat use, blood. see bottom.

Oxytocin & vasopressin derive from ancestral vertebrate vasocontin 500ma.

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