Comparison Of Aging-related Gene Expression In Different Tissues Of Omi/HtrA2 Knockout Mice

Cell senescence,a process,is comprehensively caused by various stress reactions.These stress reactions can lead cells into an irreversible state of growth stagnation.In terms of maintaining normal cell operation,responding to different injury and stimuli and decreasing cell death for the body,the balance of mitochondrial homeostasis is an essential and important organelle.When the mitochondrial antioxidant defense system,division and fusion,biosynthesis and other processes are abnormal,which will lead to serious mitochondrial dysfunction,irreversible cell growth stagnation,neurodegenerative diseases,cancer,cardiovascular diseases,diabetes and other aging-related diseases.Omi/HtrA2,a serine protease,belongs to the HtrA family.Under normal circumstances,it is located in the mitochondrial membrane gap.It has an important effect on maintaining mitochondrial homeostasis.Omi/HtrA2,a nuclear coding protein,has an N-terminal mitochondrial targeting sequence.Omi/HtrA2 has one or two C-terminal PDZ domains,which can activate its serine protease activity.For HtrA2^mnd2 mice,occurrence of imissense mutation of S276C of Omi/HtrA2 results in loss of Omi/HtrA2 protease activity.The performance of mice is muscle atrophy and nerve degeneration.In this experiment,in order to verify the difference of mitochondrial function and oxidative stress in various tissues,expression of mitochondrial function-related genes in brain,heart,liver and kidney of HtrA2^mnd2 mice was detected by real-time quantitative PCR.And the aim is to explore Omi/HtrA2 to participate in cell dysfunction on the basic of the changes of mitochondrial function-related genes.Methods:Subjects of the study:wild type mice?+/+?and HtrA2^mnd2 mice?-/-?.Real-time quantitative PCR and other experimental methods were used to detect mRNA expressions of mitochondrial biosynthesis genes PGC-1?,antioxidant genes HO-1,GSTA1,mitochondrial fusion genes Mfn1,Mfn2,Opa1,mitochondrial fission genes Fis1,Drp1,autophagy related genes P62,Map1lc3b,Lamp2 and other genes.Automatic microplate reader was used to detect MDA content and SOD activity.One-way ANOVA statistical method was used to compare the expression differences of mitochondrial biosynthesis,antioxidant stress,fission fusion,autophagy and other aging-related genes in different tissues of HtrA2^mnd2 mice.The possible mechanism of Omi/HtrA2 affecting cell aging and other functions through mitochondria wais discussed.Results:1.Compared with wild?+/+?mice,the growth of HtrA2^mnd2nd2 mice stopped about25 days after birth.It did not gain weight.About 30 days later,it showed skeletal muscle atrophy and some other signs.The survival time of mice was about 45 days.2.The results of real-time quantitative PCR showed that compared with wild type?+/+?,the mRNA expression level of mitochondrial biosynthetic gene PGC1-?of in the brain was only significantly reduced for HtrA2^mnd2 mice.However,the mRNA expression level of PGC1-?in the heart,liver and kidney increased,which indicated that there was the lowest mitochondrial biosynthesis level in the brain of HtrA2^mnd2mice and the highest mitochondrial biosynthesis level in the kidney.3.The results of real-time quantitative PCR showed that compared with wild?+/+?mice,the mRNA expression level of antioxidant gene HO-1 in the kidney increased for HtrA2mnd2 mice and it significantly decreased in the heart,liver and brain.The mRNA expression level of antioxidant gene GSTA1 was significantly reduced in the heart,liver and brain.The results of ELISA showed that the MDA content in the heart,liver and kidney decreased and that of in the brain significantly increased.Except liver,SOD activity in the heart,liver and brain all decreased.4.The results of real-time quantitative PCR showed that compared with wild type?+/+?,the mRNA expression level of mitochondrial fusion genes Mfn1 and Mfn2of HtrA2^mnd2 mice increased in the kidney,and it decreased significantly in the liver and brain.The mRNA expression level of fusion gene Opa1 was significantly reduced in the heart,liver,kidney and brain.The mRNA expression level of mitochondrion fission gene Fis1 was significantly reduced in the liver,kidney and brain.However,mRNA expression level of mitochondrial division gene Drp1 was significantly increased in the heart,liver,kidney and brain.5.The results of real-time quantitative PCR showed that compared with the wild type?+/+?,the mRNA expression level of autophagy gene P62 of HtrA2^mnd2 mice decreased significantly in the brain,heart,liver and kidney.The mRNA expression levels of autophagy genes Lamp2 and Map1lc3b increased in the brain.However,it decreased in the heart,liver and kidney.Conclusion:1.The posture and life cycle are considered as the basis of judgment.HtrA2^mnd2mice have aging performance,which can prove that Omi/HtrA2 may be connected with aging of tissue cell.2.There are some differences in the expression of genes related to mitochondrial biosynthesis and mitochondrial fission fusion genes in the heart,liver,kidney and brain of HtrA2^mnd2 mice.Especially in brain tissue,it shows a decrease in the expression level of genes related to mitochondrial biosynthesis,an increase in the expression level of mitochondrial division and autophagy genes,which can indicate that there was a significant decrease in the mitochondrial function of brain tissue.3.Brain tissue damage caused by Omi/HtrA2 gene mutation may be connected with the reduction of antioxidant level.On the basic of the literature,we speculate that the tissue damage caused by mitochondrial dysfunction may be connected with the degree of requirement of tissue to oxygen.