AQP4 Gene Cloning And Its Expression Mechanism Of Resistance To High Altitude Cerebral Edema In The Yak (Bos Grunniens)

To investigate the resistance mechanism of plateau animals to high altitude cerebral edema (HACE) induced by high altitude reaction as well as to study the coping mechanism of plateau animals to extreme environment such as cold and hypoxia in Qinghai-Tibetan Plateau,this experiment is conducted. Yak aquaporin 4 (AQP4) gene cloning, contrast and analysis of gene sequence and immunohistochemistry about the expression of adult yak cerebral aquaporin4 in different functional area are carried out. The results are as follows:1.Part of AQP4 gene sequence from yak is cloned and the sequence length is 211bp coding for 56 amine acids (gene sequence number:JF798424). Comapred with cattle (Bos tarus),sheep (ovis aries linnaeus) and human, the homology of that yak AQP4 gene sequence are 97%(the total length is 1256bp),94%(the total length is 1046bp) and 90%(the total length is 1101bp).The translated yak AQP4 amino acid sequence shares 96% homology with that of Cattle. The amino acids from position 1 to 32 are outside structure which from position 33 to 56 are membrane spaning domain; in the secondary structure analysis, the amino acids curl's structure is from 1 to 22,26 to 30 and 52 to 56,the spiral structure is from 31 to 51,meanwhile those structures are connected by a little amount fold structure (from 23 to 25);the amino acids from 15 to 29 and 23 to 56 of that sequence have apparent hydrophobicity as well as there is no apparent hydrophilic region.2. In this paper, the AQP4 immune reaction products are labeled brown as well as there is nothing in negative control group.In cingulate gyrus, precentral gyrus, thalamus, caudate nucleus and hippocampus from yak brain, there are AQP4 expressed in most of the fusiform, ovate and conoid neurons and in a few of the round neurons, glial cells and capillaries. Statistical analysis show that both the immunostaining area (S) and the integral optical density (IOD) value of different functional area (including precentral gyrus in cortex, cingulated gyrus in cortex,thalamus in diencephalon, caudate nucleus in corpus striatum and hippocampal formation in iimbic system) in yak brain are significantly lower than that in cattle brain (P<0.01) Among every functional areas of yak cerebral tissues, there is consistency of AQP4 expression area (S) and total optical density (IOD) values. The S and IOD values of cingulate gyrus are the highest in all five parts while that of cortial area (cingulate gyrus and precentral gyrus) are significantly higher than other parts (thalamus, caudate nucleus and hippocampus).AQP4 expression characteristic between different parts of cattle brain is as same as that in yak brain.Conclusions:The cloned part of yak AQP4 amino acid sequence is located on cell membrane,and the behind segment is transmembrane structure and has apparent hydrophobicity so that could not transport water which is suspected to be a nonfunctional position of AQP4. There is comparatively large discrepancy of cell water permeability and metabolism function among different functional area in yak brain, distinct peers of a functional area and distinguished type cells in the same functional area and peer which may be have different resistance to HACE. Compared with cattle, the yak has stronger adaptability to extreme environment such as cold and hypoxia in Qinghai-Tibetan Plateau, that's to say, the yak has powerful resistance to HACE based on its gene structure and rationale of protein expression.