使用不帶電中性核酸探針於原位雜交技術檢測微核醣核酸之研究;MicroRNA In Situ Hybridization with Phosphate-methylated oligonucleotides (nDNA) Probe

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Title:	使用不帶電中性核酸探針於原位雜交技術檢測微核醣核酸之研究;MicroRNA In Situ Hybridization with Phosphate-methylated oligonucleotides (nDNA) Probe
Authors:	李采璘;Li, Tsai-Ling
Contributors:	化學工程與材料工程學系
Keywords:	原位雜交技術;微核醣核酸;核酸分子;專一性;In Situ Hybridization;microRNA;nucleic acid;specificity
Date:	2018-05-25
Issue Date:	2018-08-31 11:29:42 (UTC+8)
Publisher:	國立中央大學
Abstract:	微核醣核酸(microRNA)是一群非編碼的小核醣核酸分子，序列長度約為18-22個核苷酸，在基因表現的調控上扮演重要的角色；藉由和其目標信使核糖核酸(messanger RNA)的互補序列結合誘發mRNA的降解以調節基因的表現。在先前的許多研究皆指出了不正常的微核糖核酸表現量和一些人類的疾病有相當大的關聯性。因此，特定的核糖核酸可以做為疾病檢測或癒後預測的生物標記分子(biomarkers)。發展具有專高靈敏度及高專一性的檢測平台因而變成一項重要的議題；現今的檢測平台及方法包括原位雜交技術(in situ hybridization) ，逆轉錄聚合酶鏈式反應(qRT-PCR)，北方點墨法(northern blotting)，微型核糖核酸晶片定序(miRNA microarray profiling)；在上述這些技術中，僅有原位雜交技術可以達到同時檢測核醣核酸表現量及觀察在細胞或組織中的分布情形，且保有細胞或組織原有的形態。然而此技術的最大限制在於因微核糖核酸的序列長度太過於短小且核醣核酸本身較脆弱易被降解的特性，若使用一般去氧核醣核酸分子(DNA)做為檢測探針的情況下，檢測結果缺乏專一性。在本研究中，我們在原位雜交技術中使用的檢測探針是一種由本實驗室開發研究的核酸類似物，一種不帶電中性核酸，是將單股的去氧核醣核酸上的核酸骨幹上帶負電的磷酸根基團修飾上甲基，形成甲基磷酸三酯鍵 (MPTE)，使其不帶電；因此與其互補的序列做雜交時，靜電排斥的作用力下降形成較穩定的MPTEDNA/DNA雙股螺旋結構，因而具有較高的檢測專一性。且其疏水性的性質使得中性DNA更容易穿進細胞膜。我們利用此種探針於檢測HCT116人類結腸癌細胞株的外源微核糖核酸(miR-524-5p)及在結腸癌細胞株內oncomiR，內源核醣核酸(miR-21)。實驗結果皆顯示在相同的實驗條件下，修飾過MPTE的探針比起一般DNA探針具有較高的訊號強度，我們可以看到使用優化設計的不帶電中性核酸探針於原位雜交技術檢測微核醣核酸的可行性且可成功的提高檢測訊號且維持檢測專一性。期望藉由建立使用中性DNA於ISH的方法，將此種核甘酸發展成有潛力的疾病治療用藥。 ;MicroRNAs (miRNAs) are a cluster of small, non-coding RNA molecules, generally 18-22 nucleotides in length, that play important roles in regulating gene expression by binding to the target messenger RNAs (mRNAs) and inducing mRNAs degradation. Previous studies have shown several correlations between aberrant miRNAs expression and a variety of human diseases. Hence, typical miRNAs are considered as diagnostic and prognostic biomarkers. That is to say, the need of developing highly sensitive and specific detection methods is necessary. Current detecting methods include In Situ Hybridization (ISH), Real time PCR, northern blotting, and miRNA microarray profiling technology. Above these methods, only ISH provide miRNA information about both expression level and localization in a single cell level. However, the main challenge of using DNA oligonucleotides as detecting probe is that the results lack of specificity since the small size and the nature fragile characterization of the target miRNA. In this study, we applied an alternative DNA analogue, which contains site-specific neutral methyl phosphotriester internucleotide linkages (MPTE), shows improved the hybridization properties due to the reduction of electrostatic repulsion between the double strands MPTEDNA/RNA duplex. And the lipophilic character allow the probe transport through cell membrane easily. In Situ Hybridization methods were performed to visualize mimic exogenous miR-524-5p we transfected into HCT116 cell lines (human colon cancer cell lines) and the well-known oncomiR in colon cancer cell lines, endogenous miR-21, by 3’-digoxigenin (DIG) labelled MPTE modified probe. Through optimal design of the modification of MPTE, the results demonstrated improved hybridization efficiency while remaining detecting specificity. Based on the success of applying MPTE probe on detecting miRNA through ISH, we expected the potential ability of MPTE modified oligonucleotides developing into theoretic agent.
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