The development of new branches within biology laid the foundation for understanding the subtle mechanisms of cell functioning in general and of its components. It became apparent that the genetic apparatus occupies the central place in a cell. Thus, a prospect of directed influence on the structure and functioning of the genetic apparatus, in particular genome-editing, was introduced. In human bodies, cells are organized into an extremely complex molecular structure responsible for immunity. However, bacteria also have their own, but much simpler molecular immunity systems, which protect the bacterial cell from pathogens. In 1987, a Japanese researcher found in the genome of Escherichia coli a region containing numerous repeats and called it the CRISPR locus (1, p. 2). Later, CRISPR-Cas9, prokaryotes adaptive system, was adjusted to be used as a genome-editing tool (1). The discovery of 1987 launched the future of CRISPR-Cas9 – one of the most promising technologies of the last years.
The innovation allows researchers to manipulate the genome in just a few days, and it is the first such accurate tool designed for this purpose. Besides the relatively short time of editing, the device also may be considered simple to use: making changes to CRISPR-Cas9 set-up so that various genomic regions could be edited is deemed straightforward (2). Gupta et al. (1) note apropos the directness of the tool usage “the system serves as yet another that nature holds some of the simplest solutions to some of the most complicated problems” (p. 12). CRISPR-Cas9 also renders generating disease models, for instance, for cancer, more unchallenging – this brings researchers closer to a comprehensive picture of the mechanisms behind genetic disorders and a number of illnesses (3). In this way, one of the primary advantages that the genome-editing tool possesses is its rapidity and straightforwardness in usage.
Another significant positive side that CRISPR-Cas9 has is the costs associated with its usage. The genome-editing tool may be considered a comparatively inexpensive technique to manipulate a gene or gene regions (2). Gupta et al. conducted a comparative study between CRISPR‑Cas9 and several other similar technologies – Zinc finger nuclease (ZFN) and transcription activator-like effector nuclease (TALENs) – noting their cost-effectiveness among other measurements (1). The researchers note that CRISPR‑Cas9 is the most inexpensive tool, followed by TALENs, and ZFN’s usage necessitates the most prominent budget among the technologies (1). The costs linked to CRISPR-Cas9 are part of what makes this tool revolutionary, as financial limitations may be one of the reasons for research postponement or even cancellation.
The fact that the implementation of CRISPR-Cas9 in one’s research does not entail significant expenses leads to another advantage that this genome-editing tool has brought. The discussed above positive effects of CRISPR-Cas9 made it somewhat popular within the researcher circles. The number of publications connected to the technology has grown significantly over recent years, and, for instance, PubMed has approximately fifteen thousand research papers registered under the corresponding category (2, para. 3). Shepherd (2) states that “considering the publication bias towards positive results, this means that there are probably thousands of additional labs, projects and scientists around the world using this system” (para. 3). Hence, the introduction of CRISPR-Cas9 potentially popularized gene-editing research and topics within it.
Despite the numerous benefits connected to the technology in question, it perhaps could not be considered a perfect gene-editing tool. One of its drawbacks is related to the notion of efficacy. Even though Gupta et al. describe CRISPR-Cas9 as having high targeting efficacy and specificity, especially compared to TALENs and ZFN, contradictory opinions also may be found (1). By editing efficiency, the number of well-edited cells is understood. As stated by Shepherd, the editing tool is not always 100% accurate (2). This fluctuation that does not reach the absolute percentage of accurateness may not nullify the efforts that a potential researcher invested in the operation, but rather exacts mindfulness and cautiousness when deciphering the editing results.
An additional disadvantage that usage of CRISPR-Cas9 entails is a lack of specificity in a practical setting. The technology’s off-target effects result in the appearance of mutations in genetic regions that were supposed to be unaffected directly by editing, even if all the procedures were respected and the guide RNA sequence is particular to the genome (2). Wang et al. (43) explain that “tight regulation of Cas9 expression and activity may potentially reduce its off‑target effects and, thus, this is a prerequisite for the future use of Cas9 in clinical applications” (p. 247). Consequently, the presence of off-target effects in editing is an issue that may be solved and does not hinder the potential of CRISPR-Cas9 and its inclusion into medical trials.
The times when the primary research method for biologists was observation are long gone. Biology in this century has changed qualitatively to a degree due to the development of such branches as biochemistry, biophysics, molecular biology, and molecular genetics. CRISPR-Cas9 is one of the culminations of these transformations. Undeterred by the issues described, this genome‑editing technology eclipses others by its low cost, straightforwardness in use, and relatively high efficacy. CRISPR-Cas9 remains a significant breakthrough in biological sciences, developed in close conjunction with medicine, the significance of which is yet to be understood.
References
Gupta, D., Bhattacharjee, O., Mandal, D., Sen, M. K., Dey, D., Dasgupta, A., Kazid, T., A., Guptaa, R., Sinharoyb, S., Acharyaa, K., Chattopadhyaye, D., Ravichandiranc, V., Royc S., & Ghosh, D. (2019). CRISPR-Cas9 system: A new-fangled dawn in gene editing. Life Sciences, 232, 1‑15.
Shepherd, C. (2019). CRISPR-Cas9 genome-editing: Weighing the pros and cons. Bitesize Bio.
Wang, H., La Russa, M., & Qi, L. S. (2016). CRISPR/Cas9 in genome-editing and beyond. Annual Review of Biochemistry, 85(1), 227–264.
Footnotes
- Gupta et al., 2019.
- Shepherd, 2019.
- Wang et al., 2016.