Role Of Mfn2 Gene In Mitochondrial Respiratory Chain In Congenital Cataract Formation

Objective:Mitofusin2 is a highly conserved GTPase which is located on the mitochondrial outer membrane and encoded by nuclear genes,plays crucial role in mitochondrial fusion.Mitochondrial dynamics is essential for maintaining mitochondrial DNA stability and respiratory capacity.In addition,the stability of mitochondrial functions is associated with cell stress.Oxidative stress has been confirmed as an important factor of cataract.In this project,we employed the approach of specifically inactivate Mfn2 on the eye surface ectoderm to observe the development of lens in order to figure out the function of Mfn2 in respiratory capacity,meanwhile,to investigate the mechanisms in congenital cataract formation.Methods:In this experimental research,Cre-loxP approach was used to specifically inactivate Mfn2 genes on surface ectoderm to establish Mfn2 conditional knockout mice.The genotype of mice was detected by PCR.Le-Cre Mfn2^flox/floxlox/flox mice were selected as experimental group.Littermate mice carrying Mfn2^flox/floxmice were selected as control group.P15,1M,2M,3M mice were used in this study.Slit lamp was used to examine the lenses in the experimental group and the control group.The weights of eyeballs and lens of the mice in experimental group and those in control group were measured by the precision electronic scale.The ATP dependency of the light-emitting,luciferase-catalyzed oxidation of luciferin was used to measure the mitochondrial ATP level in both groups.The enzymatic activity of complex I and complex IV in the lens of mice in both groups was assayed by the ultraviolet spectroscopy.The experimental data was analyzed by the SPSS 24.0 software.Results:The observation of slit lamp showed that the nuclear opacity lens of the mice in experimental group began at 1 M,sooner than that of the control mice.The weights of eyeballs and lens of the mice in experimental group were less than those in control group.At P15 and 1 M,ATP levels of the lens in experimental group were lower than the lens in control group（P<0.05）.Over time,at 2M and 3M,the ATP levels of the lens in experimental group were significantly lower than the lens of the age-matched mice in control group（P<0.01）.At P15 and 1 M,compared with the control,the lens of experimental mice had lower activity of complex I in the mitochondrial respiratory chain（P<0.05）.During aging,the lens of the experimental mice at 2M displayed much lower activity of complex I compared with that of the age-matched controls（P<0.01）.Although the difference between two groups of the activity of complex IV were not statistically significant at P15,the lens of experimental mice at 1M and 2M displayed much lower activity of complex IV compared with that of the age-matched controls（P<0.05）.Conclusion:1.Loss of Mfn2 on surface ectoderm results in congenital cataract.2.Loss of Mfn2 on surface ectoderm results in reduced of the weight of eyeballs and lens.3.Mfn2 conditional knockout affected the mitochondrial respiratory chain of the lens by reducing the activity of complex I and complex IV which perhaps to be the main reason for congenital cataract in mice.