RESUMO
As the main carrier of oxygen delivery in the blood circulation system, hemoglobin (Hb) plays a key role in the adaptation of animals to high altitude hypoxia.In this paper, we combined analysis of genome, transcriptome, molecular evolution, homology modeling and molecular dynamics simulation, and explored the molecular mechanisms of increased blood oxygen affinity of Pseudopodoces humilis.Our results showed that the prenatal expressed p gene was highly expressed in the adult Pseudopodoces humilis (RPKM = 32.22) compared to Parus major (RPKM = 0), and this may result in the presence of two additional p-type Hbs with high oxygen affinity in the blood of P.humilis, i.e.(al>p)2 and (aAp)2.The PA25G-A and pA55L-I mutations may increase the van der Waals force between the B and D helices, which might eventually make the entire Pv subunit more compact and finally reduce the number of hydrogen bonds between a dimers, hence the transition from T state to R state is prone to occur.The two mutations of (3a43A-S and pA44S-N could change the conformation and polarity of the heme pocket opening, thus making the solution easier to flow into/out of the heme pocket and therefore facilitating the gas exchange.The pA90E-K mutation in P.humilis has undergone strong positive selection, which could increase the basicity of pA-type Hb, thereby offsetting the decrease in Hb-02 affinity caused by the Bohr effect.In addition, we also found that aA44P-S and pA43A-S mutations may increase the hydrophilicity of otA and pv type Hbs, which is beneficial to the accumulation of Hb to a higher concentration in red blood cells.Collectively, the prenatal Hb genes highly expressed in the adult together with the genetic based changes in intrinsic 0, affinity and physicochemical property of aA and pA Hb could be the main causes for the increase in blood oxygen affinity of P.humilus.
RESUMO
BACKGROUND: Changes of red blood cell in peripheral blood and bone marrow erythropoietic system in plateau pikas are of great significance for hypoxic adaptation. OBJECTIVE: To explore the hypoxic adaptation of erythropoietic system in plateau pikas by comparing the morphological changes of peripheral blood and bone marrow between plateau pikas and rats exposed to hypoxia. METHODS: There were 12 healthy wild plateau pikas and 12 clean Sprague-Dawley rats and were randomly divided into experimental and control groups, 6 in each group. The experimental group animals were fed in a simulated 5 000 m altitude hypobaric hypoxia chamber for 28 consecutive days, and the control group animals were fed in the laboratory at 2 260 m altitude. RESULTS AND CONCLUSION: (1) The diameter of the erythrocytes was smaller and red blood cell count was higher in plateau pikas than those in the rats of control group. After 28 days of hypoxia, red blood cell count, hemoglobin and hematocrit were increased in both experimental groups (P < 0.001), but the increased rate of plateau pikas were less than that of the rats. The mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration showed no significant changes in plateau pikas. (2) Results of bone marrow smear showed that the proportion of polychromatic and orthochromatic erythroblasts had no significant changes in plateau pikas after hypoxia, but increased significantly in the rats (P < 0.05). (3) Hematoxylin-eosin staining results of the sternum indicated that the immature erythroblasts islands did not change significantly in plateau pikas, but increased significantly in rats. (4) So the erythroid changes in peripheral blood and bone marrow of plateau pikas before and after hypoxia are significantly lower than those of the Sprague-Dawley rats, and they may be related to the hypoxia adaptation mechanism.