RNA Interference
What is RNAi?
RNA interference (RNAi) is the process by which double stranded effectively silences the expression of a target gene [1]. Its discovery has been attributed to Andrew Fire and Craig Mello, who also won the 2006 Noble Prize in Physiology or Medicine for the achievement [2]. RNAi is used for studying the function of a gene by observing the phenotypes that result after it has been silenced. Therefore, this technique falls under the category of reverse genetics [3]. The image to the right describes how RNAi functions on a molecular level (click to enlarge).
While this method is similar to knock-out mutants, RNAi has its limitations. There are some tissues that do not respond to RNAi well, particularly the nervous system. In addition, RNAi may not completely knock out the expression of a protein due to experimental variability [5]. However, if these limitations can be surpassed RNAi is many times favored over knockout organisms because it is more economic. |
Image Credit: [4]
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RNAi and HFE
RNAi can be performed in a variety of model organisms. In my search for previous research that had performed RNAi experiments on HFE homologues I was able to find two: one in C. elegans and D. melanogaster, which have a human HFE homologues called DRAG-1 and Malvolio, respectively. I was able to find the results of these experiments using WormBase and FlyBase. Below are the results of the experiments.
Analysis
It is interesting that when the HFE homologue is knocked out in each of these model organisms one of the possible resulting phenotypes was lethality. While having mutations in HFE in humans is not lethal, perhaps not possessing these iron regulating proteins in these organisms is more detrimental because of their small size.
In addition, I found it interesting that there were behavioral and taste perception defects in the fruit fly. This suggests that, in this organism, not being able to regulate iron resulted in damage to the nervous system. This may be akin to how an overload of iron in the human body can result in damage to a variety of organs.
In addition, I found it interesting that there were behavioral and taste perception defects in the fruit fly. This suggests that, in this organism, not being able to regulate iron resulted in damage to the nervous system. This may be akin to how an overload of iron in the human body can result in damage to a variety of organs.
References
1. Timmons, L., Tabara H, Mello, C.C., and Fire, A.Z. (2003). Inducible systemic RNA silencing in Caenohabditis elegans. Molecular Biology Cell, 14(7), 2972-83.
2. Fire, A., Xu, S., Montgomery, M.K., Kostas, S.A., Driver, S.E., and Mello, C.C. (1997). Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans. Nature, 391, 806-811. doi: 10.1038/35888
3. Worm Book: Reverse genetics: http://www.wormbook.org/chapters/www_introreversegenetics/introreversegenetics.html
4. Hardin, J., Bertoni, G., and Kleinsmith, L. J. World of the Cell. 8th ed. New York: Pearson, 2012. Print.
5. Sugimoto, A. (2004). High-throughput RNAi in Caenorhabditis elegans: genome-wide screens and functional genomics. Differentiation, 72(2-3), 81-91. DOI: 10.1111/j.1432-0436.2004.07202004.x
2. Fire, A., Xu, S., Montgomery, M.K., Kostas, S.A., Driver, S.E., and Mello, C.C. (1997). Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans. Nature, 391, 806-811. doi: 10.1038/35888
3. Worm Book: Reverse genetics: http://www.wormbook.org/chapters/www_introreversegenetics/introreversegenetics.html
4. Hardin, J., Bertoni, G., and Kleinsmith, L. J. World of the Cell. 8th ed. New York: Pearson, 2012. Print.
5. Sugimoto, A. (2004). High-throughput RNAi in Caenorhabditis elegans: genome-wide screens and functional genomics. Differentiation, 72(2-3), 81-91. DOI: 10.1111/j.1432-0436.2004.07202004.x