Establishment and Characterization of Behavioral Changes in the Nuclear Localization Human α-Synuclein Transgenic Mice

<b>Objectives:</b> This study aimed to establish a transgenic mouse model expressing nucleus-localized human α-synuclein (α-syn) to investigate its impact on the central nervous system and behavior and the underlying mechanisms involved. <b>Methods:</b> A nuclear localization sequence (NLS) was added to the end of the human SNCA (hSNCA) gene. Subsequently, an empty vector and a mammalian lentiviral vector of the hSNCA-NLS were constructed. Transgenic mice were generated via microinjection, with genotyping and protein expression confirmed by PCR and western blotting. Only male mice were used in subsequent behavioral and molecular experiments. Immunofluorescence identified the colocalization of human α-syn with the cell nucleus in mouse brain tissues. Behavioral changes in transgenic mice were assessed using open field, rotarod, and O-maze tests. qPCR and Western blotting detected expression levels of genes and proteins related to inflammation, endoplasmic reticulum stress (ERS), and apoptosis. Bulk RNA sequencing was used to screen for differentially expressed genes and signaling pathways. <b>Results:</b> We successfully constructed a transgenic mouse model expressing human α-syn. Human α-syn was widely expressed in the heart, liver, spleen, kidneys, and brain of the mice, with distinct nuclear localization observed. Behavioral assessments demonstrated that, by 2 months of age, the mice exhibited motor dysfunction alongside astrocyte proliferation and neuroinflammation. At 6 months, the elevated expression of ERS-related genes (ATF6, PERK, and IRE1) and activation of the PERK-Beclin1-LC3II pathway indicated progressive ERS. By 9 months, apoptotic events had occurred, accompanied by significant anxiety-like behaviors. Bulk RNA sequencing further identified key differentially expressed genes, including IL-1α, TNF, PERK, BECLIN, GABA, IL-6α, P53, LC3II, NOS, and SPAG, suggesting their involvement in the observed pathological and behavioral phenotypes. <b>Conclusions:</b> The nuclear localization human α-syn transgenic mice were successfully established. These findings demonstrate that nucleus-localized α-syn induces early motor deficits, which are likely mediated by neuroinflammation, whereas later anxiety-like behaviors may result from ERS-induced apoptosis. This model provides a valuable tool for elucidating the role of nuclear α-syn in Parkinson's disease and supports further mechanistic and therapeutic research.