臨床神経学

<シンポジウム07―1>Atypical types of dementia 非典型認知症

Dementiaの分子病態:Epigenetics研究から

岩田 淳

東京大学医学系研究科神経内科〔〒113―8655 東京都文京区本郷7―3―1〕
同 分子脳病態科学

The pathological hallmark of neurodegeneration is presence of intra- and extra neuronal inclusion bodies such as Lewy bodies in Parkinson's disease, senile plaques and neurofibrillary tangles in Alzheimer's disease. These are consisted of aggregated conformationally abnormal proteins. The precise mechanism of aggregation remains unknown, but increased expression of aggregation-prone proteins can lead to their aggregation. For example, in Down syndrome, duplication of the 21st chromosome, which contains the amyloid beta precursor protein (APP) gene, leads to accumulation of amyloid beta and Alzheimer's disease pathology and multiplication of APP gene is shown to be the cause of familial Alzheimer's disease. Moreover, in rare cases of PD, duplication or triplication of SNCA gene leads to alpha-synuclein accumulation, with triplication producing a more severe phenotype than duplication, suggesting that SNCA expression level determines the severity of the pathology. Lastly, animal models of neurodegenerative disorders are generated by over-expression of causal genes, further supporting the conclusion that increased gene expression is related to pathogenesis. Additional evidence indicates that SNCA promoter polymorphisms increases alpha-synuclein expression and increases susceptibility to sporadic PD. In addition to promoter polymorphisms, epigenetic modification can alter downstream gene expression. Epigenetic regulation includes histone modification and DNA methylation, of which CpG island methylation can be gene-specific; in several different cancers, CpG methylation inhibits binding of the transcription machinery, causing silencing of a specific oncogene, which leads to carcinogenesis. In central nervous system disorders, CpG methylation has been associated with psychiatric disorders, such as autism and schizophrenia. We found several cases of Parkinson's disease with epigenetic abnormality in SNCA gene. Thus, we believe that studying epigenetics can provide previously unknown causes for dementia and other neurodegenerative disorders.
Full Text of this Article in Japanese PDF (111K)

(臨床神経, 51:928−929, 2011)
key words:認知症,エピジェネティクス,DNAメチル化

(受付日:2011年5月19日)