Kırmızı Un Beetle Larva RNA Girişim,<em> Tribolium castaneum</em
Summary
RNA enterferans (RNAi) tabanlı gen demonte teknikleri Tribolium araştırma özünde vardır. Burada, biz Tribolium castaneum'ların bizim larva RNAi tekniğinin bir bakış sağlar. Larva RNAi araştırmacılar farklı bağlamlarda gen fonksiyonlarını incelemek için izin, kayıp fonksiyon-fenotiplerine hızlı erişim sağlayan basit, ama güçlü bir tekniktir.
Abstract
Kırmızı un böcekleri, Tribolium castaneum, tam açıklamalı genom sekansı, transpozon bazlı genetik dönüştürme ve etkin bir RNA girişimi (RNAi) de dahil olmak üzere genetik ve geliştirme çalışmaları için, deney araçları bir repertuar sunar. Bu avantajlarının yanında, RNAi dayalı gen demonte teknikleri Tribolium araştırma özünde vardır. T. confusum mümkün basitçe böceğin vücut boşluğuna çift kollu RNA (dsRNA) enjekte edilmesiyle herhangi bir yaşam safhasında RNAi bir hale getirmektedir, sağlam bir sistemik RNAi tepki gösterir.
Bu yazıda, T. bizim larva RNAi teknik bir bakış sağlamak castaneum. Protokol T. uygun aşamasında (i) izolasyonu, Enjeksiyon için confusum larva ve enjeksiyon ayarı için, (ii) hazırlanması, ve (iii) dsRNA enjeksiyonu. Larva RNAi kaybı fonksiyon-fenotipinin hızlı erişim bize sağlayan basit, ama güçlü bir tekniktirBirden fazla gen demonte fenotiplerle yanı sıra hypomorphic fenotipleri bir dizi dahil, es. Hemen hemen tüm T. yana confusum dokuların hücre dışı dsRNA duyarlıdır, larva RNAi teknik araştırmacılar dış ortama doğru yanıtların organizma, genetik olarak dahil çeşitli bağlamlarda, dokuların ve çeşitli çalışma sağlar. Ayrıca, bu tekniğin basitliği T. yapma, araştırma daha öğrenci katılımını uyarır Bir sınıf ortamında kullanmak için ideal bir genetik sistem castaneum.
Introduction
Kırmızı un böceği, Tribolium castaneum nedeniyle RNA girişimi (RNAi) 1-3 gerçekleştirme kolaylığı kısmen biyoloji çeşitli alanlarda popülerlik kazanıyor. RNAi dayalı gen demonte teknikleri bilim adamları kayıp fonksiyon-kompleks genetik yöntemler kullanarak olmadan analizleri yapmak için izin verir. T. confusum mümkün böceğin vücut boşluğuna 4-6 olarak iki-şeritli RNA (dsRNA), basit enjeksiyon yoluyla herhangi bir aşamada RNAi bir hale getirmektedir, sağlam bir sistemik RNAi tepki gösterir. Birden fazla genin eşzamanlı devirme da T. mümkündür Aynı zamanda 7,8, iki veya daha fazla farklı dsRNA molekülleri enjekte confusum. Buna ek olarak, hypomorphic fenotiplerin bir dizi 8 dsRNA enjekte konsantrasyonunu azaltmak suretiyle oluşturulabilir. Bu özellikler T. geleneksel ileri genetik RNAi tabanlı ters genetik teknikleri cazip alternatifler yapmak castaneum. Yana neredeyseTüm T. confusum dokuların bu teknik, araştırmacılar farklı bağlamlarda dokuların çeşitli çalışma sağlar, hücre dışı bir dsRNA molekülleri 9 karşı hassastır. Ayrıca, bu rapor T. RNAi performans odaklansa da castaneum, burada açıklanan birçok prosedürler diğer böcekler için de geçerlidir. Isteyenler kaybı-fonksiyonu T. ilgi kendi bağlamlarında analizleri gerçekleştirmek için Dolayısıyla, bu protokol yararlıdır castaneum, yanı sıra diğer böcekler için bir RNAi tabanlı tekniği uygulamak isteyen araştırmacılar için.
Larva halinde dsRNA'yı enjekte larva, pupa olmak üzere böceği yaşam evrelerinde, çeşitli fonksiyonel analiz sağlar, ve yetişkin 4,5,10 sahneliyor. Biz daha önce moleküler biyoloji prosedürleri 11 olmak üzere bizim genel larva RNAi protokolü bildirdi. Mevcut raporda, biz en iyi görsel yardımcıları ile açıklanmıştır dsRNA'nın enjeksiyon prosedürleri açıklayan odaklanmak. Biz sağlayabilirayrıntılı adım-adım enjeksiyon işlemleri yanı sıra iyi ve kötü enjeksiyon örnekler. Bu görsel protokolü önceki protokol tamamlar ve kombine edildiğinde, onlar T. larva RNAi prosedürlerin daha kapsamlı bir görünüm sağlar castaneum. Buna ek olarak, RNAi, fizyolojik araştırma için RNAi bazlı deneylerde uygulama başarısını, hem de bir öğretim laboratuarda larva RNAi protokolünün uygulanabilirliğini etkileyebilecek dsRNA molekülleri için parametreleri tartışırlar.
Protocol
Representative Results
Discussion
There are a number of important issues that need to be considered to guarantee the success of RNAi, including the length and concentration of the dsRNA molecules, competition among different dsRNA molecules (when attempting multiple knock down), and the possibility of Off-Target Effects (OTE).
dsRNA Length
The length of dsRNA molecules affects the efficiency of the systemic RNAi response, with a longer dsRNA being more efficient to trigger RNAi7,14,15 (though the longer limit of dsRNA is currently unknown). The dsRNA length needs to be longer than 50 bp to induce effective RNAi in T. castaneum7. dsRNA between 150 bp and 500 bp appears to be ideal for RNAi experiments. Although longer dsRNA molecules can also be used, they will have an increased chance of OTE and the gene-cloning step will become increasingly difficult.
dsRNA Concentration
Different degrees of gene knockdown can be achieved depending on the concentration of dsRNA. 1 μg/μl appears to be a reasonable starting concentration, which often produces a near-null phenotype (may vary depending on the gene(s) of interest). RNAi can be performed with a higher concentration (e.g., 7-8 μg/μl) to obtain a stronger RNAi phenotype. RNAi with a serial dilution of dsRNA can sometimes be beneficial to produce a series of hypomorphic phenotypes (Supplemental Data of Tomoyasu et al. 20098, and Borràs-Castells unpublished data).
RNAi Competition
Multiple gene knockdown can be accomplished in T. castaneum by injecting several different dsRNA molecules simultaneously. However, it is also known that having several different dsRNA molecules present within the organism often results in competition between the dsRNAs for access to the RNAi components7,14. It is important to use the same length and the same concentration for all dsRNA when attempting multiple gene knockdown to avoid one dsRNA out-competing the others (although, further adjustments of the dsRNA length and concentration may be required when the expression levels greatly differ among the target genes). We, as well as others, have successfully performed double and triple knockdown (e.g., Tomoyasu et al. 200516, Tomoyasu et al. 200917, and Yang et al. 200918). Although feasible, quadruple RNAi (or more) might be challenging, as it would likely cause significant reduction of RNAi efficiency for all four target genes.
Off-targeting
OTE is an inherent concern for RNAi-based approaches. One way to minimize OTE is to identify regions in the target gene that share similar sequences with other genes and avoid these regions when designing dsRNA. A simple BLAST analysis against the T. castaneum predicted gene set can identify such regions. Several online tools also allow evaluation of potential OTE (e.g., E-RNAi19). Performing RNAi for two non-overlapping regions of the target gene is an easy and efficient way to eliminate the possibility that observed phenotypes are caused by OTE. The possibility of OTE is minimized if RNAi for two non-overlapping regions produce the same phenotypes (unless the two non-overlapping regions share a similar sequence).
Evaluating gene knockdown by means other than phenotypic analyses is often critical to effectively present RNAi-related data. Two major ways to evaluate gene knockdown are qRT-PCR and western blot analysis. qRT-PCR is a convenient way to measure the level of the target mRNA, and has been used in many RNAi-related studies including those in T. castaneum (see Miller et al. 20127 for example). However, caution must be taken, as we have recently seen some cases in which the target mRNA level is up-regulated by RNAi (though the protein product is down-regulated) (Borràs-Castells unpublished data). It is currently unknown if this RNAi induced mRNA up-regulation can be widespread or unique to certain genes. Western blot analysis is another way to confirm gene knockdown. This method is quite reliable as it measures the amount of the final protein product. The requirement of a specific antibody against the protein product of the target gene is a downside to this approach. Utilizing multiple independent measurements in addition to phenotypic analysis will increase the confidence of the phenotypic data obtained by RNAi-based analysis.
Since its conception in T. castaneum, RNAi has primarily been used to study gene function in development and pattern formation. These T. castaneum developmental studies have been highly successful in characterizing evolutionarily conserved and diverged functions of genes (reviewed in Denell 20081 and Klingler 20042). However, RNAi-based studies in T. castaneum are not limited to developmental biology. For example, RNAi can be utilized to study gene function in a wide range of physiological and behavioral responses, including stress tolerance, predation, aggression, mate choice, activity patterns, and defense mechanisms.
One difficulty of applying RNAi to these contexts is the likelihood of pleiotropic effects. Often, genes of interest will have a variety of roles throughout the T. castaneum life cycle, thus making the removal of genes without unintended phenotypic effects difficult. However, the ability to easily perform RNAi at a variety of stages can often be an effective strategy for avoiding these pleiotropic effects. For instance, performing RNAi in adults instead of larvae or pupae might allow us to circumvent unintended lethality caused by gene knockdown during early development. The flexibility of the RNAi response in T. castaneum thus makes this model an attractive choice for adapting RNAi to experiments of gene function in physiological and behavioral responses.
The T. castaneum system is also ideal for use in a teaching laboratory. T. castaneum can be easily cultured on a flour/yeast mixture at room temperature (25 °C) without frequent subculturing, and RNAi techniques in T. castaneum are simple enough to be adapted to a laboratory with young, learning scientists. As RNAi is becoming an essential technique in a variety of biological fields, it is crucial that students are exposed to this technique. The straight-forward nature of the larval RNAi technique in T. castaneum also encourages more students to be involved in research, making T. castaneum a prime candidate for a classroom oriented genetic system.
Divulgaciones
The authors have nothing to disclose.
Acknowledgements
We thank the Center for Bioinformatics and Functional Genomics (CBFG) at Miami University for technical support. This work was supported by Miami University start-up grant (YT), and National Science Foundation (YT: IOS 0950964).
Materials
| Name of Reagent/ Equipment | Company | Catalog Number | Comments/Description |
| Organic whole wheat flour | Heartland Mill Inc. Kansas | G1 | |
| Brewer’s Yeast | MP Biomedicals | 2903312 | Sift yeast with #35 stainless sieve before use. Wear protective mask and cover the sieve with plastic wrap, as the sifted yeast is a fine particle and respiratory hazardus. |
| 6 oz plastic Drosophila stock bottles | Fisher Scientific | 11-888 | |
| Sieve | Fisher Scientific | 04-881N | 8 in. dia. x 2 in.D. Use #25 (Nominal opening 710µm) for larvae, pupae, and adults. |
| Sieve | Fisher Scientific | 04 881 10P | 8 in. diameter #35 (Nominal seive opening: 600µm) Stainless Steel Sieves, 8 in. dia. x 2 in.D. This sieve is ideal to remove clumps from yeast powder. |
| Sieve receiver | Fisher Scientific | 04-866B | 8 in. diameter |
| 1.5 quart spouted sample pan | Seedburo Equipment Co. | Model 33 | collection pan |
| Incubator | BioCold Environmental Inc | BC26-IN | Keep it 30C with 70% humidity. |
| Na2HPO4 | Fisher Scientific | S374500 | |
| NaH2PO4 | Fisher Scientific | S397-500 | |
| KCl | Fisher Scientific | P217-500 | |
| Food dye | Kroger | green, blue, or red preferable | |
| Microscope glass slide | Fisher Scientific | 22-038-103 | |
| Tack-It Over&Over | Aleene's | Repositionable glue for sticky slides. Double sided tape can be used as an alternative, however, we found that the adhesiveness varies. | |
| Plastic CD case | Amazon | ||
| Boroslilicate Glass capillary | Sutter Instrument | BF100-50-15 | O.D. 1 mm, I.D. 0.5 mm, 15 cm. without filament |
| Needle puller | Sutter Instrument | P-87 or P-97 | |
| Silicone seal | Narishige | HI01PK01 | 2.5 mm |
| Removable mounting putty | Loctite Fun-Tak | ||
| Compressed gas duster | OfficeMax | OM96091 | |
| Forceps | Fine Science Tool | 11231-30 | Dumoxel #3 (to manipulate beetles) |
| Forceps | Fine Science Tool | 11252-20 | INOX #5 (to break needle tips) |
| Ethyl ether, anhydrous | Fisher Scientific | E138-500 | |
| Nylon mesh | Flystuff/Genessee Scientific | 57-102 | 120-um pore size/49% open area |
| Media bootle 100-ml | VWR | 89000-926 | |
| Stereomicroscope | Zeiss | SteREO Discovery V12. Injection microscope. | |
| Stereomicroscope | Fisher/Zeiss | 12-070-513 | Stemi2000. Use to break the needle and place larvae onto the sticky slide. |
| X-Y mechanical stage | Zeiss | 4354600000000000 | |
| X-Y mechanical stage | Microscopenet.com | A512 | Inexpensive alternative |
| Manipulator | Narishige | M-152 | |
| Magnetic stand | Narishige | GJ-1 | |
| Glass capillary holder | Narishige | IM-H1 | |
| 30-ml disposable syringe | BD syringe | 309650 | BD Luer-Lok Tip |
| Four-way stopcock | Cole-Parmer Instrument Co. | EW-30600-03 | Stopcocks with Luer Connections; 4-way; male slip |
| art paint brush | Amazon | Art Advantage Oil and Acrylic Brush Set, 24-Piece | Any general paint brush will work. |
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