小鼠視覺皮質層印記基因表現圖譜

Abstract

中文摘要 染色體印記，是為經外遺傳的調控，而形成特殊、基因表達視其親源而定的現象。其主要發生於哺乳類的神經系統，因此，若其機制上的異常即會造成神經發育、或心智功能上的疾病。雖然染色體印記對於腦部功能是如此的重要，但印記基因明確的數目、及何為印記基因，到目前為止仍未定案。而會有如此的困難度一部份來自於腦部結構的多樣性。印記基因的表達除視其親源而定外，也會受到不同的細胞種類、發育上的時間點、以及環境的影響。為了明確的辨識印記基因，我們藉由在不同的細胞型態、以及發育時間點上，建立一篩選平台。技術上，我們利用次世代定序、以及基因轉殖鼠來達成此目標，而此篇論文所介紹，在小鼠視覺皮質層獨立興奮性神經元的方法，也可應用在不同的細胞型態上。在另一方面，為了看到環境對於印記狀態的操弄，我們選擇在完全無光線飼養下(24小時全暗)、比較正常環境飼養(12小時光照、12小時黑暗)此兩種情況。藉此，破壞小鼠視覺皮層的正常發育，來看光線經驗的不同對於印記狀態的影響。藉由上述的方法，希望我的工作可以讓我們更加地了解印記基因在腦部扮演的角色、以及為何在演化上發展出如此獨立的機制。更重要的，因而印記基因異常而造成的疾病，也可藉由這樣的策略發展治療方法。

Abstract Genomic imprinting is an epigenetic process by which certain genes are expressed in a parent-of-origin-specific manner. Genomic imprinting predominantly occurs in the mammalian nervous system. Dysfunctional genomic imprinting causes various neurological and psychiatric disorders. Despite the importance of genomic imprinting in brain function, the number and identity of imprinted genes have been proposed, but are still debated. The key obstacles to advance the field of genomic imprinting in the brain are the complex expression patterns of imprinted genes and the heterogeneous nature of the brain. The expression of imprinted genes can be regulated by different cell types, developmental stages and the environment. In order to solve the urgent problems of this field, I first developed a platform to comprehensively profile imprinted genes in a specific cell type under different developmental stages. Using the technique of deep sequencing and the advantage of engineered mice, I can determine the genomic imprinting status of excitatory neurons in mouse visual cortex. The success of the platform I developed here could apply to the profiling of the genomic imprinting status in other cell types. Regarding to the environmental effect on the imprinting status of the brain, I chose the dark rearing condition (24hr Dark) in comparison to the normal rearing (12hr/12hr, Dark/Light). Under this manipulation, we destroyed the maturation of visual cortex and determined the effect of light experience on the imprinting status of mouse visual cortex. My comprehensive profiling work of genomic imprinting status in the brain could deepen our understanding about why our brain developed genomic imprinting during evolution. More importantly, the knowledge gained here may provide therapeutic strategies for genomic imprinting disorders.