示差メチル化の測定<em> INS</em>バイオマーカー膵島のβ細胞死などのヒト血清試料中のDNA種
Summary
Islet β cell death precedes development of type 1 diabetes, and detecting this process may allow for early therapeutic intervention. Here, we provide a detailed description of how to measure differentially methylated INS DNA species in human serum as a biomarker of β cell death.
Abstract
The death of islet β cells is thought to underlie the pathogenesis of virtually all forms of diabetes and to precede the development of frank hyperglycemia, especially in type 1 diabetes. The development of sensitive and reliable biomarkers of β cell death may allow for early therapeutic intervention to prevent or delay the development of diabetes. Recently, several groups including our own have reported that cell-free, differentially methylated DNA encoding preproinsulin (INS) in the circulation is correlated to β cell death in pre-type 1 diabetes and new-onset type 1 diabetes. Here, we present a step-by-step protocol using digital PCR for the measurement of cell-free INS DNA that is differentially methylated at cytosine at position -69 bp (relative to the transcriptional start site). We demonstrate that the assay can distinguish between methylated and unmethylated cytosine at position -69 bp, is linear across several orders of magnitude, provides absolute quantitation of DNA copy numbers, and can be applied to samples of human serum from individuals with new-onset type 1 diabetes and disease-free controls. The protocol described here can be adapted to any DNA species for which detection of differentially methylated cytosines is desired, whether from circulation or from isolated cells and tissues, and can provide absolute quantitation of DNA fragments.
Introduction
1型糖尿病（T1D）は、自己反応性T細胞1によるインスリン産生膵島β細胞の破壊により特徴付けられる自己免疫疾患です。 T1Dの診断は、通常、インスリン欠乏の証拠としてケトアシドーシスを呈する可能性があるリーン、若い個体で高血糖（血糖値>が200mg / dl）の測定時に行われます。 T1Dの診断時に、β細胞機能及び質量の実質的な損失の証拠がある（50〜 – 90％）2。臨床研究では、診断時に制定されたいくつかの免疫調節薬は、疾患の臨床的寛解をもたらしたβ細胞機能（およびおそらく質量）が、いずれの安定化の発展のためにコールを調達している知見をもたらしました病気の早期発見のためとの併用療法3,4の有効性の長手方向の追跡のためのバイオマーカーの。国際コンソーシアムの取り組み、などヒース5の国立研究所のヒト膵島研究ネットワークコンソーシアムはね、T1D中のβ細胞ストレスと死に焦点を当てたバイオマーカーを開発する必要性を強調してきました。
9 –これらの取り組みに沿って、私たちのグループなどが最近β細胞6を死んでから主に生じる循環、エピジェネティック修飾されたDNA断片を測定するバイオマーカーアッセイを開発しました。現在まで発表されたアッセイの全てにおいて、焦点は他の細胞型と比較して、コードおよびプロモーター領域における非メチル化CpG部位のより大きな程度を実証するヒト遺伝子をコードするプレ（INS）の定量にされています。非メチル化INS DNA断片の放出は（壊死性、アポトーシス）β細胞を瀕死から主に発生していると仮定しました。我々の最近の研究では位置で、若者にいることを非メチル化とメチル化の両方INS DNAの上昇を示した-69 bpの（トンへの相対彼は新たな発症T1Dで観察され、そして一緒にこの集団6のような特異的バイオマーカーを務めた）転写開始部位。これらのバイオマーカーアッセイは、（ウラシルに非メチル化シトシンを変換するために、無傷のメチル化シトシンを残して）単離されたDNAの重亜硫酸塩変換に続く商用スピンキットを用いて、血清または血漿からの無細胞DNAの単離を伴います。
この報告書では、我々は、血清からの無細胞DNA、重亜硫酸塩変換、および示差的メチル化INS DNAのための液滴のデジタルPCR（以下、デジタルPCR）の性能の単離を、血清サンプル収集の技術的側面を説明します。
Protocol
Representative Results
Discussion
DNAメチルトランスフェラーゼによってシトシンのメチル化は、多くの遺伝子における転写のエピジェネティックな制御を可能にします。ヒトでのINS遺伝子がほぼ独占的に膵島β細胞で発現し、その転写11のサイレンシングにINS遺伝子中のシトシンのメチル化の頻度との間に相関関係があるように表示されます。 13 –このように、ほとんどの細胞型は…
Disclosures
The authors have nothing to disclose.
Acknowledgements
This work was supported by National Institutes of Health grant UC4 DK104166 (to RGM). We wish to acknowledge the assistance of the Indiana Diabetes Research Center Translation Core supported by National Institutes of Health grant P30 DK097512.
Materials
| Red Top Vacutainer | Beckon Dickinson | 366441 | no additive, uncoated interior, 10 ml |
| Cryovial Tube | Simport | T310-3A | polypropylene, screw cap tube, any size |
| QIAamp DNA Blood Mini Kit | Qiagen | 51106 | |
| Poly(A) | Sigma | P9403 | disloved in TE buffer (10 mM Tris-Cl pH 8.0 + 1 mM EDTA) to 5 µg/µl |
| Absolute Ethanol (200 Proof) | Fisher Scientific | BP2818-500 | |
| DPBS (with CaCl and MgCl) | Sigma | D8662 | |
| 0.2 mL PCR 8-strip Tubes | MidSci | AVST | |
| 8-strip Caps, Dome | MidSci | AVSTC-N | |
| EZ DNA Methylation-Lightning Kit | Zymo | D5031 | |
| ddPCR Supermix for Probes (No dUTP) | Biorad | 1863024 | |
| Buffer Control for Probes | Biorad | 1863052 | |
| Human Unmethylated/Methylated Primer/Probe mix | Life Technologies | AH21BH1 | |
| EcoR1 | New England Biolabs | R0101L | |
| twin.tec PCR Plate 96, semi-skirted | Eppendorf | 951020346 | |
| Pierceable Foil Heat Seal | Biorad | 1814040 | |
| PX1 PCR Plate Sealer | Biorad | 1814000 | |
| QX200 AutoDG Droplet Digital PCR System | Biorad | 1864101 | |
| Automated Droplet Generation Oil for Probes | Biorad | 186-4110 | |
| DG32 Cartridge for Automated Droplet Generator | Biorad | 186-4108 | |
| Pipet Tips for Automated Droplet Generator | Biorad | 186-4120 | |
| Pipet Tip Bins for Automated Droplet Generator | Biorad | 186-4125 | |
| C1000 Touch Thermal Cycler | Biorad | 1851197 | |
| QX200 Droplet Reader | Biorad | 186-4003 | |
| ddPCR Droplet Reader Oil | Biorad | 186-3004 |
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