Genetic Techniques And Ethical Considerations

Quesstion: Discuss and about Genetic Techniques And Ethical Considerations. Answer: CRISPR-Cas9 refers to a unique technology, which holds promise in enabling medical researchers and geneticists to edit certain parts of the genome. The technology principally focuses on removal, addition, or alteration of different fragments of the DNA sequence being edited. In other words, this technology has been identified as the simplest, precise and versatile method that facilitates the process of bringing about genetic manipulation in an organism (1). Some of the most potential applications of this CRISPR-Cas9 technology encompass correction of genetic defects, improvement in the yield and hybrid vigour of crops and the treatment and prevention of several diseases. Two common examples where the3 CRISPR-Cas9 technology has been used are given below: CRISPR-Cas9 has shown its potential as a powerful genetic tool for the treatment of a plethora of medical conditions, which are related to certain genetic components such as, hepatitis B, cancer, and high cholesterol. Recent researches have been conducted to evaluate the effectiveness of this technology in treating cystic fibrosis, a hereditary disorder that is caused due to mutations in a gene encoding the CFTR protein (2). The technology has also been used for editing the genome of body cells or somatic cells. The basic mechanism by which this technology conducts the process of gene editing involves a process of delivering Cas9 nuclease that is complexed with a synthetic gRNA (guide RNA) inside a cell, thereby assisting in the process of cutting down the genome at a desired location. This allows the genes to be removed or helps in addition of new genes (3). Although this technology is used to edit the genomes that are present in the somatic cells, a lot of debate exists regarding the potential for editing germline or reproductive cells. This can be attributed to the fact that the changes that are made in these germline cells will be passed on to the next generations, thereby creating ethical complications (4). Most of the ethical issues that are related to genome editing are focused on the human germline editing. The debate regarding this germline genome editing has regained interest following the discovery of the potential of CRISPR-Cas9 to make accurate editing. Attempts hd been taken in April 2015 tom alter the DNA present in non-viable human embryos with the use of CRISPR-Cas9 technology. This research was focused on editing parts of the endogenous beta-globin gene (HBB), a mutation in which is responsible for the occurrence of beta-thalassemia among humans. Upon use of the CRISPR-Cas9 technology, low efficiency was obtained with respect to homologous recombination efficiency, which in turn contributed to the development of mosaic embryos (5). Although the purpose of the study was focussed on treating the lethal heritable disease, it was rejected due to certain ethical concerns. Most researchers suggested that although editing of the genome with the use of CRISPR-Cas9 technology could eradicate several genetic diseases, before child birth, making genetic modifications to the human embryo, commonly known as germline modifications, would be heritable and might lead to the onset of unpredictable effects on the future generation (6). Researchers have also argued that all kinds of genome editing in the human embryo with the use of this technology could also lead towards unethical or unsafe uses of the technique (7). Other ethical concerns that disapprove the use of CRISPR-Cas9 were related to the fact that none of the 85 human embryos used for the study met the criteria of showing a precisely altered beta-globin gene. They either died or showed no genetic alterations (5). Second unsuccessful attempts were also made in an experiment that attempted to alter the DNA present in non-viable embryos with the use of CRISPR-Cas9 technology, for altering CD195 or CCR5, with the aim of inducing HIV resistance. All attempts that target towards making genetically altered babies are considered irresponsible acts (8). One major ethical concern is associated with the fact that the benefits of the CRISPR-Cas9 technology must be greater than the risks that it poses on human health (9). Much attention has been given to the associated risks, owing to the damages that they create on the humans. Application of CRISPR-Cas9 is not considered ethically feasible as it involves production of several off target deleterious mutations. This fact is supported by evidences that suggest presence of high frequency off target impacts in human cells, compared to zebrafish and mice (10). Further research evidences have emphasised on the role of CRISPR-Cas9 technology in cleaving the unintended sequences, thereby resulting in mutations that lead to cell death or transformations in the cells (11). Another major ethical concern is related to the safe and efficient delivery of the CRISPR-Cas9 into the tissues and cells that are extremely difficult to infect or transfect. There is a need to probe the specificity in RNA guided experiments that use CRISPR-Cas9. Owing to the fact that gene drive, which propagates a suite of genes through a population is still in operation, there is an increased possibility of off target mutations, which in turn might increase in each generation (12). Owing to the persistent risks of transferring genes to the progenies, there is a risk of transferring these edited or modified sequences, which in turn will contribute to the transmission of negative traits. Until now, most therapeutic interventions performed in humans that focused on genome editing were performed in somatic cells. However, the experiment conducted by Chinese researchers created major concern over possibilities of bringing about alterations in the human germline. The primary difference can be attributed to the fact that intended germline genetic modifications might get transmitted. Although, genome editing in somatic cells are ethically accepted, germline cells can acquire side effects and mutations due to CRISPR-Cas9 technique, thereby transferring these unpredictable changes to future generations (13). In addition, ethical problems also exist regarding the appropriate implementation of informed consent, in cases when there are associated risks of the technology. Furthermore, efforts taken for germline modifications to generate inheritable changes have been claimed irresponsible at the International Summit on Human Gene Editing (14). Thus, further clinical research must proceed following adherence to appropriate ethical and legal guidelines for altering human gametocytes. References Shalem O, Sanjana NE, Hartenian E, Shi X, Scott DA, Mikkelsen TS, Heckl D, Ebert BL, Root DE, Doench JG, Zhang F. Genome-scale CRISPR-Cas9 knockout screening in human cells. Science. 2014 Jan 3;343(6166):84-7. Schwank G, Koo BK, Sasselli V, Dekkers JF, Heo I, Demircan T, Sasaki N, Boymans S, Cuppen E, van der Ent CK, Nieuwenhuis EE. Functional repair of CFTR by CRISPR/Cas9 in intestinal stem cell organoids of cystic fibrosis patients. Cell stem cell. 2013 Dec 5;13(6):653-8. Ran FA, Hsu PD, Wright J, Agarwala V, Scott DA, Zhang F. Genome engineering using the CRISPR-Cas9 system. Nature protocols. 2013 Nov;8(11):2281. Baltimore D, Berg P, Botchan M, Carroll D, Charo RA, Church G, Corn JE, Daley GQ, Doudna JA, Fenner M, Greely HT. A prudent path forward for genomic engineering and germline gene modification. Science. 2015 Apr 3;348(6230):36-8. Liang P, Xu Y, Zhang X, Ding C, Huang R, Zhang Z, Lv J, Xie X, Chen Y, Li Y, Sun Y. CRISPR/Cas9-mediated gene editing in human tripronuclear zygotes. Protein & cell. 2015 May 1;6(5):363-72. Bosley KS, Botchan M, Bredenoord AL, Carroll D, Charo RA, Charpentier E, Cohen R, Corn J, Doudna J, Feng G, Greely HT. CRISPR germline engineering—the community speaks. Nature biotechnology. 2015 May 12;33(5):478. Caplan AL, Parent B, Shen M, Plunkett C. No time to waste—the ethical challenges created by CRISPR: CRISPR/Cas, being an efficient, simple, and cheap technology to edit the genome of any organism, raises many ethical and regulatory issues beyond the use to manipulate human germ line cells. EMBO reports. 2015 Nov 1;16(11):1421-6. Cradick TJ, Fine EJ, Antico CJ, Bao G. CRISPR/Cas9 systems targeting β-globin and CCR5 genes have substantial off-target activity. Nucleic acids research. 2013 Aug 10;41(20):9584-92. Zhang XH, Tee LY, Wang XG, Huang QS, Yang SH. Off-target effects in CRISPR/Cas9-mediated genome engineering. Molecular Therapy-Nucleic Acids. 2015 Jan 1;4. Hwang WY, Fu Y, Reyon D, Maeder ML, Tsai SQ, Sander JD, Peterson RT, Yeh JJ, Joung JK. Efficient genome editing in zebrafish using a CRISPR-Cas system. Nature biotechnology. 2013 Mar;31(3):227. Yang H, Wang H, Shivalila CS, Cheng AW, Shi L, Jaenisch R. One-step generation of mice carrying reporter and conditional alleles by CRISPR/Cas-mediated genome engineering. Cell. 2013 Sep 12;154(6):1370-9. Fu Y, Foden JA, Khayter C, Maeder ML, Reyon D, Joung JK, Sander JD. High-frequency off-target mutagenesis induced by CRISPR-Cas nucleases in human cells. Nature biotechnology. 2013 Sep;31(9):822. Lanphier E, Urnov F, Haecker SE, Werner M, Smolenski J. Don’t edit the human germ line. Nature News. 2015 Mar 26;519(7544):410. Hampton LR. A New Era of Genome Modification. Retrieved from: https://repository.uwyo.edu/cgi/viewcontent.cgi?article=1102&context=honors_theses_16-17

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