The Effects Of Systemic Seipin Knockout On Cognitive And Depression-like Behaviors And Hippocampal Neurogenesis In Mice

Objective:To examine the effects of systemic seipin knockout on cognitive function and depression-like behavior and hippocampal neurogenesis in mice,and explore its underlying mechanism.Methods:1.Breeding systemic seipin knockout mice,mouse tails were taken to extract DNA,and the mouse genotypes were identified by semi-quantitative PCR.2.WT and seipin-sKO mice at different ages were selected(5 weeks,8 weeks,12 weeks and 18 weeks).The spontaneous alternation in the Y maze and the residence time of the Morris water maze in the target quadrant were used to analyze the effect of seipin knockout on the spatial memory ability in mice.The immobility time in FST and TST were used to analyze the effect of seipin knockout on depression-like behavior in mice.3.Hippocampal tissue sections of WT and seipin-sKO mice at different ages were selected(5 weeks and 18 weeks).The effects of seipin knockout on hippocampal neurogenesis were observed by Ki67 and DCX immunofluorescence staining.4.NSCs cultured in vitro were dissociated from neonatal mouse(Postnatal day 0,P0)hippocampal.The effect of seipin knockout on the proliferation and differentiation of hippocampal NSCs in P0 mice were detected by BrdU incorporation experiment and Tuj1 immunofluorescence staining.5.The blood glucose levels of WT and seipin-sKO mice at different ages were measured(5 weeks,8 weeks,12 weeks and 18 weeks).Pearson correlation coefficient was used to analyze the correlation between blood glucose and cognitive indicators in mice.Results:1.WT and seipin-sKO mice at different ages were used to measure spatial memory.The results of Y maze showed that the correct rate of spontaneous alternation in seipin-sKO was significantly lower than the WT group at 12 weeks and 18 weeks(P < 0.05).Compared with WT group,the Morris water maze results showed that the latency to reach the platform in seipin-sKO was significantly longer at 12 weeks and 18 weeks,at the same time,the residence time and run length in the target quadrant were significantly reduced(P < 0.05).However,there were no differences in seipin-sKO mice at 5 weeks and 8 weeks,suggesting that seipin knockout may cause cognitive impairment from in mice starting at 12 weeks.2.WT and seipin-sKO mice at different ages were used to measure depression-like behavior.In FST,the immobility time of seipin-sKO mice at 12 weeks and 18 weeks were significantly longer than the WT group(P < 0.05).And the immobility time of seipin-sKO mice in TST was also higher than WT mice at 18 weeks(P < 0.05),suggesting that seipin knockout may cause depression-like behavior in mice at 18 weeks.3.Immunofluorescence staining showed that the number of proliferation marker(Ki67)and early neuron marker(DCX)positive cells in the subgranular layer(SGZ)of seipin-sKO at 18 weeks was significantly decreased than WT mice(P < 0.05).But there was no difference between seipin-sKO and WT mice at 5 weeks,suggesting that seipin defect induces proliferation and differentiation damage of hippocampal NSCs in mice at 18 weeks.4.The results of immunofluorescence staining showed that the positive cell rates of BrdU and Tuj1 in P0 seipin-sKO hippocampal NSCs was no significant difference,compared with WT mice.It is suggested that seipin knockout may not affect the proliferation and differentiation ability of P0 hippocampal NSCs.5.The blood glucose results showed that the glucose level of seipin-sKO mice was significantly higher than that of WT mice at 12 weeks(P < 0.05)and 18 weeks(P < 0.01).And the Pearson correlation coefficient analysis results showed that the glucose levels of the mice with the Y maze correct rate of spontaneous alternation(R =-0.5462,P = 0.013),the residence time of the water maze in the target quadrant(R =-0.4614,P = 0.041)and the run length in the target quadrant(R =-0.4522,P = 0.045)has a negative correlation,respectively.Conclusion:1.Systemic seipin knockout mice showed a decline in hippocampal NSCs proliferation and differentiation ability with cognitive impairment and depression-like behavior at 18 weeks,while P0 seipin knockout mice had no change in hippocampal NSCs proliferation and differentiation in vitro.Therefore,the decrease in neurogenesis in seipin knockout mice may not be due to the lack of seipin.2.Seipin knockout mice's blood glucose gradually increased with age,statistical analysis showed negative correlation between blood glucose and cognitive learning ability of seipin mice.Therefore,we speculated that metabolic disorders caused by seipin knockout may be an important cause of cognitive impairment in mice.