探討可調節擴增CUG重複片段毒性之基因

第一型肌強直萎縮症（Myotonic dystrophy type 1）是一種顯性遺傳的罕見疾病，往往會造成病患有肌強直、白內障和心律不整的症狀。這些症狀起因於信使核糖核酸（massage RNA）發生了異常的選擇性剪接（Alternative splicing），這些異常選擇性剪接之所以發生，是因為伴隨著擴增CUG重複片段在三端非轉譯區（3’-UTR）的DMPK基因信使核糖核酸會累積在細胞核內成為核糖核酸聚集物（RNA foci）。目前，針對這樣重複三核苷酸型異常（Trinucleotide repeat disorder）的疾病沒有任何有效的治療方式，為了調查這個疾病詳細的致病機制和潛在的治療方式，我們與蕭光明老師及潘惠錦老師實驗室合作，建立了一種線蟲模型（Caenorhabditis elegans）可以表現在三端非轉譯區伴隨CUG重複片段的報導基因，我們可以在這個線蟲模型當中觀察到有明顯核糖核酸聚集物累積在肌肉細胞的細胞核內，這個現象與病患是相符合。進一步的，為了找尋可以調節CUG重複的毒性，蕭老師實驗室利用這模型進行了核糖核酸干擾（RNA interference）的篩選，我們進一步發現有一些具有調節毒性作用的基因，像是drh-1, rde-4 和wrn-1，可以有效的影響含有CUG重複片段的報導基因之表現，特別是drh-1對於CUG重複片段具有專一性。drh-1編譯著一種與切丁酶相關的解旋酶（Dicer-related helicase），對於核糖核酸干擾生合成路徑（RNAi synthesis pathway）的啟動扮演關鍵的角色，而drh-1的突變會造成細胞核和細胞質內的含CUG重複片段的信使核糖核酸增加，並縮短了線蟲模型的壽命。根據drh-1核糖核酸干擾生合成路徑所扮演的角色，我們選出了這條路徑中的一些基因並解調查這些基因與CUG重複片段的關聯，結果顯示這些基因大部分都會影響含有CUG重複片段的報導基因，屬於增強核糖核酸干擾的基因突變會減少含有CUG重複片段的報導基因之表現，如ergo-1，另一方面，核糖核酸干擾缺失的基因突變會加強含有CUG重複片段的報導基因之表現，如rrf-1。簡而言之，我們的研究結果指出CUG重複片段的毒性可以被我們所發現的調節基因向上或是向下的調控。

關鍵字

強直性肌肉失養症；核醣核酸干擾；重複片段

並列摘要

Myotonic dystrophy type 1, an autosomal dominant disease, torments patients with myotonia, cataracts and cardiac arrhythmia. These symptoms are caused by the abnormal alternative splicing, resulting from the RNA foci formation of the aberrant DMPK mRNA with expanded CUG repeats in 3’UTR. There is no treatment conducted specific to this trinucleotide repeat disorder up to date. In order to investigate the detail of the mechanism and the potential cure, we collaborated with Kuang-Ming Hsiao’s lab to generate the worm model expressed the reporter gene with CUG repeats in 3’UTR. Like myotonic dystrophy patients, the obvious RNA foci were detected in the nucleus of muscular cells in C. elegans. Further, Dr. Hsiao lab performed an RNAi and identify rde-4 that modulate the expansion of a gfp reporter with CUG repeats. We have expanded the list of modulator genes, including drh-1 and wrn-1. Among these, the effect of drh-1 is specific to CUG repeats. DRH-1, a dicer-related helicase, is required for the initiation phase of RNA interference synthesis pathway. Loss of drh-1 would increase the amount of CUG mRNA in nucleus and cytosol and the shorten life span. Some other members of the RNA interference pathway were found to influence the reporter with expanded CUG repeat. In summary, we demonstrated C. elegans as a valuable disease model to study CUG toxicity. Our results revealed a potential modulatory role of RNAi synthesis pathway on MD pathogenesis.

並列關鍵字

myotonic dystrophy ； RNA interference ； CUG repeat

參考文獻

Brenner, S. (1974). The genetics of Caenorhabditis elegans. Genetics, 77(1), 71-94.

Google Scholar

Chatterjee, N., Lin, Y., Santillan, B. A., Yotnda, P., Wilson, J. H. (2015). Environmental stress induces trinucleotide repeat mutagenesis in human cells. Proc Natl Acad Sci U S A, 112(12), 3764-3769. doi:10.1073/pnas.1421917112

Google Scholar

Chen, K. Y., Pan, H., Lin, M. J., Li, Y. Y., Wang, L. C., Wu, Y. C., Hsiao, K. M. (2007). Length-dependent toxicity of untranslated CUG repeats on Caenorhabditis elegans. Biochem Biophys Res Commun, 352(3), 774-779. doi:10.1016/j.bbrc.2006.11.102

Google Scholar

Cooper, T. A. (2006). A reversal of misfortune for myotonic dystrophy? N Engl J Med, 355(17), 1825-1827. doi:10.1056/NEJMcibr064708

Google Scholar

Day, J. W., Ricker, K., Jacobsen, J. F., Rasmussen, L. J., Dick, K. A., Kress, W., . . . Ranum, L. P. (2003). Myotonic dystrophy type 2: molecular, diagnostic and clinical spectrum. Neurology, 60(4), 657-664.

Google Scholar

國際替代計量

探討可調節擴增CUG重複片段毒性之基因

未授權

主題瀏覽