Investigation of the neurodegenerative impact of CAG expansion in TBP gene through Taiwan neurodegenerative patients and transgenic mouse model

• Main Author: 林承岳
• Other Authors: Hsiu-Mei Hsieh-Li
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/88055471199656175138

碩士 === 國立臺灣師範大學 === 生命科學研究所 === 94 === TATA binding protein (TBP) is a general transcription factor that plays an important role in initiation of transcription. TBP gene is located in chromosome 6q27 and contains a CAG/CAA trinucleotide repeats region in 5’ end which encodes a polyglutamine tract. It was reported that TBP is involved in numerous neurodegenerative diseases including Huntington’s disease (HD), Alzheimer’s disease (AD) and spinocerebellar ataxia type 17 (SCA17). SCA17 is an autosomal dominant cerebellar ataxia (ADCA). It has been known that the length of polyglutamine tract encoded by the CAA/CAG repeats is related to the disease progression. The range of CAG repeats of TBP gene is 31- 42 in normal population and 43 - 63 in SCA17 patients. To investigate the TBP trinucleotide expansion effect on neurodegeneration, we conducted genotyping analysis in both normal and neurodegenerative disease populations in Taiwan. We found that the most common TBP allele contains 36 repeats. We identified six individuals with expanded CAG repeats from two families originally diagnosed as PD and Dementia, respectively. To establish SCA17 disease animal model, we generate transgenic mice expressing the human TBP gene with either normal or expanded CAA/CAG tracts under the control of Purkinje cell-specific promoter, Pcp2/L7 promoter. Seven transgenic mouse lines have been identified. The existence of transgene in the mouse genome was confirmed by Southern blot analysis. RNA and protein expressions were detected by RT-PCR ad Western blot analyses, respectively. By behavior observation, we found that hTBP109Q line-16 and line-54 transgenic mice have a hind-limb clasping phenotype, which was also reported by Huntington’s disease transgenic mice. Among the 7 transgenic lines, line-69 and line-54 showed significant reduction in the Rota-rod performance compared to their wild-type littermates. We also observe ataxia phenotype of these two lines in their elder stage. Immunohistochemical analysis has shown that the Purkinje cell in line-69 transgenic mouse cerebellum were lost severly. In conclusion, we have successfully generated the hTBP transgenic mice as SCA17 animal model. This model should help us to gain insight about the role of TBP in neurodegeneration and eventually could lead to rational therapeutic protocol designing.