Neurodegeneration Study On Zebrafish nicastrin Heterozygous Mutants

• Main Authors: Wen-Jie Chen, 陳文傑
• Other Authors: Yun-Jin Jiang
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/vg43cc

碩士 === 國立臺灣大學 === 分子與細胞生物學研究所 === 106 === Nicastrin is a subunit of γ-secretase which functions to regulate binding of substrates to γ-secretase and has been implicated in neurodegeneration. However, the mechanism is unclear. Previously, we discovered several neurodegenerative phenotypes, including increased hyperphosphorylated Tau proteins and cognition deficits in aged nicastrinhi1384/+ zebrafish (unpublished data). Accordingly, we intended to comprehensively examine if nicastrinhi1384/+ zebrafish can be a vertebrate model to study neurodegeneration. In the present work, we conducted a visual motor response test on nicastrinhi1384/+ zebrafish larva and uncovered that they were more active under light stimulus than wild type zebrafish larva. Besides, original T-maze behavioral tests on nicastrinhi1384/+ zebrafish demonstrated that memory of 12 and 18 month nicastrinhi1384/+ zebrafish were impaired compared to wild type zebrafish at the same age after excluding the influence of mobility variation. However, as the food which had been used in the previous behavioral tests was run out and unavailable, we switched to a new kind of food and failed to recapitulate the original behavioral tests results in the latter behavioral tests. Nevertheless, memory of nicastrinhi1384/+ zebrafish was still worse than wild type at 18 month of age. On the other hand, transcriptomic analysis on the brains of subject zebrafish of behavioral tests by using microarray showed that nicastrin mRNA level was downregulated in nicastrinhi1384/+ zebrafish, whereas mRNA expression of other γ-secretase subunits was not affected, which were verified by qPCR experiments. Last but not least, disease and functional analysis showed neurodegeneration associated phenotypes were activated, while neuronal survival and functions associated phenotypes were inhibited, implicating that nicastrinhi1384/+ zebrafish have age-dependent neurodegeneration at transcriptional level. However, TUNEL staining displayed no extensive neuronal apoptosis in the telecephalon of 18 month nicastrinhi1384/+ zebrafish. In conclusion, nicastrinhi1384/+ zebrafish larva displayed higher activity than wild type under light stimulus, and the mechanism needs to be further clarified. On the other hand, we verified the expression of nicastrin was reduced in the brains of adult nicastrinhi1384/+ zebrafish by both microarray and qPCR. Furthermore, both behavioral and transcriptomic analysis demonstrated the trend of age-dependent neurodegeneration in nicastrinhi1384/+ zebrafish, suggesting that nicastrinhi1384/+ zebrafish have potential to be a neurodegeneration model. In the future, we should examine other neurodegeneration phenotypes, such as neuroinflammation, neuronal loss, neuritic dystrophy, and synaptic loss in the brains of aged nicastrinhi1384/+ zebrafish.