Interrogation The Function Of L1 In Adult Hippocampal Neurogenesis

Adult Hippocampal Neurogenesis(AHN)has the capacity to modulate the structure and function of hippocampal neuronal microcircuits and repair neurodegenerative disorders.Nonetheless,the regulatory factors,regulatory mechanisms,and potentials for the repairing of AHN still need extensive investigation.Existing studies have shown that the long interspersed nuclear elements-1(L1)with retrotransposition capability have diverse insertion sites and copy numbers in the human brain neuronal genome,which may be one of the material and structural bases for the mosaicism of neuronal genomes and consequently result in neuronal morphological and functional diversity.Overexpression of L1 can impact neurogenic gene expression and biological processes.Yet,the mechanism and physiological role of endogenous L1 in modulating neurogenesis in vivo remain unknown.To study the association between in vivo L1 expression and AHN,this study confirmed the L1 temporal expression during AHN.Immunohistochemical analysis revealed that as mice aged,L1 expression increased in radial glia-like cells but decreased in immature and mature neurons.Simultaneously,the number of radial glia-like cells,neural precursor cells,immature and mature neurons decreased gradually.Subsequently,the reverse transcriptase inhibitor,Lamivudine,was employed to suppress L1 reverse transcription activity in the adult mice hippocampus region.The results demonstrated that Lamivudine successfully decreased the expression level of L1,and the number of radial glia-like cells,immature and mature neurons,with the exception of neural precursor cells,was also dramatically reduced.This shows that L1-mediated retrotransposition may interfere with neural precursor cell differentiation.Considering that Lamivudine may also inhibit other retrotransposons,such as SINE,in cells,this thesis utilized CRISPR/Cas Rx technology to construct specific L1 knockdown mice(L1 KD mice)and their control mice(Lac Z KD mice)targeting neural stem cells in the hippocampal region in order to investigate the regulatory role of L1 in the AHN process.The results demonstrated that the reduction of L1 expression in radial glia-like cells in the hippocampus area increased the number of neural precursor cells and decreased the number of immature neurons significantly.Last but not least,behavioral investigations of spontaneous Y-maze,water maze,new object recognition,and new location recognition in both mouse groups revealed no significant differences in spatial learning memory capacity and long-term memory capacity in L1 KD mice.The findings of the compulsive Y-maze and contextual fear conditional studies revealed,however,that the short-term memory capacity of L1 KD mice was much better than that of Lac Z KD mice.In conclusion,L1 can participate in cell fate determination processes such as survival,differentiation,and maturation of neural precursor cells during AHN,and its knockdown can improve mice’s capacity for short-term memory.Thesis shows an important role for L1 in the early development of hippocampal neurons,adding to the understanding of the biological process of adult neurogenesis that reshapes brain function,while offering a concept-of-proof for functional research of genomic dark matter.