观察与端粒的定量和重复序列用荧光<em>原位</em>杂交（FISH）与PNA探针<em>秀丽隐杆线虫</em
Summary
We report a concise procedure of fluorescence in situ hybridization (FISH) in the gonad and embryos of Caenorhabditis elegans for observing and quantifying repetitive sequences. We successfully observed and quantified two different repetitive sequences, telomere repeats and template of alternative lengthening of telomeres (TALT).
Abstract
Telomere is a ribonucleoprotein structure that protects chromosomal ends from aberrant fusion and degradation. Telomere length is maintained by telomerase or an alternative pathway, known as alternative lengthening of telomeres (ALT)1. Recently, C. elegans has emerged as a multicellular model organism for the study of telomere and ALT2. Visualization of repetitive sequences in the genome is critical in understanding the biology of telomeres. While telomere length can be measured by telomere restriction fragment assay or quantitative PCR, these methods only provide the averaged telomere length. On the contrary, fluorescence in situ hybridization (FISH) can provide the information of the individual telomeres in cells. Here, we provide protocols and representative results of the method to determine telomere length of C. elegans by fluorescent in situ hybridization. This method provides a simple, but powerful, in situ procedure that does not cause noticeable damage to morphology. By using fluorescently labeled peptide nucleic acid (PNA) and digoxigenin-dUTP-labeled probe, we were able to visualize two different repetitive sequences: telomere repeats and template of ALT (TALT) in C. elegans embryos and gonads.
Introduction
端粒可以防止异常融合和降解染色体末端。哺乳动物端粒是由G-丰富的六聚体重复，TTAGGG和shelterin复合物。线虫的端粒重复序列是相似的哺乳动物（TTAGGC）的。大多数真核生物利用端粒酶端粒重复添加到他们的染色体末端。然而，10 -癌细胞的15％利用端粒酶独立的机制，被称为端粒（ALT）3的替代延长。此前，我们报道了端粒重复序列及其相关序列，命名为TALT，端粒酶的突变系存活的关键不育2端粒扩增。
端粒长度通过定量PCR或通过Southern印迹，其中提供总端粒-4,5,6,7-的平均长度测量。在全基因组测序数据端粒重复的读取次数也总端粒8含量的指标。虽然仙GLE端粒长度分析（STELA）可以提供一个单一端粒的长度，它不能提供端粒9的空间信息。而POT-1 :: mCherry报告蛋白提供在体内的端粒的空间信息，它不能代表双链端粒长度为POT-1是一个单链端粒结合蛋白10。
而上述的方法提供了重复序列的平均信息，原位杂交（FISH）荧光允许观察染色体规模的量和感兴趣的个体的序列的空间图案。代替的DNA的纯化，组织或细胞被固定到保持在FISH本地空间信息。因此，鱼为个别重复序列，如端粒重复序列的观察定量和定性的工具。
这个协议提供了两个TELO同时检测的有效方法基于从先前描述的方法11,12的改进仅仅是与其它重复。C.线虫幼虫或成虫多细胞生物体具有高度分化的细胞。细胞的异质性阻碍对大量端粒斑点的定量分析。为了最大限度地提高了分析的细胞数，胚胎分离并散布在用于FISH聚赖氨酸包被的载玻片。此外，该协议也可以与免疫结合。
作为该协议的工作证明，我们表明，它是可能的观察和量化两个不同的重复序列。针对TALT1 DNA探针，用简单的PCR结合地高辛的dUTP产生。那么这个TALT1探针和荧光标记的端粒PNA探针杂交同时进行。随后，地高辛被规范的免疫荧光法检测。我们在座的地方TALT1在TRT-1共定位与端粒的代表图像</eM>幸存者。
Protocol
Representative Results
Discussion
我们的协议的主要优点是过程的，但无细胞结构的形态明显损坏的简单性。几个步骤C.进行了优化线虫 FISH在此协议。成功鱼的关键步骤包括探针标记，胚胎和渗透固定。地高辛的dUTP标记方法提供了通过PCR或缺口转译一个易于使用的标记方法。要标记长的靶序列，缺口平移是首选。在这种情况下，探头应用适当的限制性酶消化，以促进探针的渗透。不推荐生物素-dUTP标记，因为生物素…
Divulgations
The authors have nothing to disclose.
Acknowledgements
Mutant worm strains were kindly provided by the Caenorhabditis Genetics Center. This research was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (grant number: HI14C1277).
Materials
| PNA probe | PANAGENE | custom order | |
| Anti-Digoxigenin-Fluorescein, Fab fragments | Roche | 11207741910 | use 1:200 diluted in PBST |
| Digoxigenin-dUTP | Roche | 11573152910 | |
| Bovine serum albumin | SIGMA-ALDRICH | A-7906 | |
| Paraformaldehyde | SIGMA-ALDRICH | P-6148 | prepare 4% paraformaldehyde by heating in DW with few drops of NaOH. add 0.1 volume of 10x PBS. |
| Vectashield | Vector Laboratories | H-1200 | |
| Hybridizaiton solution | 3X SSC, 50% formamide, 10% (w/v) dextran sulfate, 50 ug/ml heparin, 100 ug/ml yeast tRNA , 100ug/ml sonicated salmon sperm DNA | ||
| Hybridizaiton wash solution | 2X SSC, 50% formamide | ||
| Formamide | BIONEER | C-9012 | toxic |
| Methanol | Carlo Erba | ||
| Acetone | Carlo Erba | ||
| Heparin | SIGMA-ALDRICH | H3393 | make 10 mg/ml for stock solution |
| Dextran sulfate | SIGMA-ALDRICH | 67578 | |
| 10X PBS | For 1 Liter DW : 80 g NaCl, 2.0 g KCl, 27 g Na2HPO4:7H2O, 2.4 g KH2PO | ||
| PBST | 1X PBS, 0.1% tween-20 | ||
| Polysorbate 20 | SIGMA-ALDRICH | P-2287 | Commercial name is Tween-20 |
| Poly-L-Lysine solution (0.1 % w/v) | SIGMA-ALDRICH | P-8920 | prepare fresh 0.01 % w/v solution before use |
| M9 | 3 g KH2PO4, 6 g Na2HPO4, 5 g NaCl, 1 ml 1 M MgSO4, H2O to 1 L | ||
| Bleaching solution | 20% sodium hypochlorite, 0.5 M KOH | ||
| Antibody buffer | 1X PBST, 1mM EDTA, 0.1% BSA, 0.05% Sodium azide (toxic) | ||
| Blocking solution | Antibody buffer with 5% bovine serum albumin (BSA) | ||
| illustra Microspin G-50 | GE healthcare | 27-53310-01 | |
| 20X SSC | To make 1L, 175.3 g of NaCl, 88.2 g of sodium citrate, H2O to 1 L, adjust pH to 7.0 | ||
| 2X SSCT | 2X SSC, 0.1 % tween-20 | ||
| 10x digoxigenin-dUTP mix | 1 mM dATP, 1 mM dGTP, 1 mM dCTP, 0.65mM dTTP, 0.35mM DIG-11-dUTP | ||
| PCR purification columns | Cosmo genetech | CMR0112 | |
| Glass cleaner / ULTRA CLEAN | Dukssan pure chemicals | 8AV721 | |
| Multi-well glass slide | MP biomedicals | 96041205 | |
| Nematode growth media | to make 1 L, 3 g of NaCl, 17 g of agar, 2.5 g of peptone, H2O to 974 mL. Autoclave and cool the flask. Add 1 mL of 1M CaCl2, 1 ml of 4 mg/mL cholesterol in ethanol, 1 ml of 1 M MgSO4, 25 mL of 1 M KPO4. | ||
| Levamisole | SIGMA-ALDRICH | 196142 | |
| Razor | Feather | blade No. 11 | |
| Rnase A | Enzynomics | ||
| BSA | SIGMA-ALDRICH | A7906 | |
| Equipments | |||
| Confocal microsope | Zeiss | LSM 510 | EC Plan-Neofluar 100x was used as objective lens. |
| Dry block / aluminum block | Labtech | LBH-T03 | Set temperature to 80℃ |
| Humid chamber | Plastic box filled with paper towel soaked in DW | ||
| Image Analysis Software | Dr. Peter Landsdorp | TFL-telo | http://www.flintbox.com/public/project/502 |
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