Paper Example on Retinitis Pigmentosa

Introduction

Retinitis pigmentosa refers to a disorder of the genetics which causes people to lose vision. The incidence of loss of vision is as a result of the breakdown that occurs leading to the retina losing cells. The retina is an eye tissue which is sensitive to light and lines the back of the eye (Hartong et al. 2006). The main symptom of this disorder is that an individual has difficulties seeing during the nighttime and they also lose peripheral vision. The loss of vision in the individual is progressive starting from 18 years of age and evolves to legal blindness when one is at age 45 (Bittner et al. 2018). There is no cure for this disorder, but optogenetic therapy is useful. The biological technology for this disorder involves using light to control neurons found in the living tissues. The modification is such that it expresses a protein that is sensitive to light. The CRISPR-Cas9 is a tool used for the purposes of editing in technology that enables medical researchers to edit a particular genome where processes such as removal, addition or alteration of DNA sections of the sequence is made possible (Hsu et al. 2014). The tool is useful for genetic manipulation and can cure retinitis pigmentosa by ending mutations in the retina.

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Preclinical research about the study of CRISPR-Cas9 and its use in Retinitis pigmentosa shows that the presence of MERTK mutations in rodents cause the phagocytizing of the RPE cells which eventually lead to loss of vision because the RPE cells get separated from the photoreceptors (Zhong et al. 2015). The CRISPR-Cas9 tool helped to demonstrate the removal of mutations in the debris due to loss of photoreceptors is able to allow the renewal of the outer segments so that their vision could survive for at least seven months which is a time span that is three times longer compared to instances where the eye is not treated (Vagni et al. 2017). The use of Enzyme Cas9 is to cut the DNA strands in the photoreceptor cells in their specific location where there is an addition or removal of the DNA in rodents (Cabral et al. 2017). The RCS rat has been commonly used as a sample for experiments since it has RPE cells that are dysfunctional that cannot undergo phagocytizing to ensure shedding of the fragments on the outside. Thus, there is an accumulation of debris on the photoreceptors and the RPE cells.Clinical research in humans involving the CRISPR-Cas9 and its therapy for RP shows that progressive degeneration of the retina area can be countered by the use of this tool (Jones et al. 2016). Rod-cone dystrophy is a common form of RP where humans experience night blindness as the initial symptom. Similarly, these patients also take a longer time to adjust to changes in lighting. Restriction of the visual fields occurs and people are uncomfortable in bright lights because of gene mutations (Deslandes et al. 2018). CRISPR-Cas9 contains a piece of RNA known as guide RNA and it comprises of RNA sequence where is located has a more extended RNA scaffold (Wu et al. 2016). The enzyme is thus made to cut at the right genome point in the mutation to remove the cells and ensure better vision at night.

Conclusion

Therapies such as using the CRISPR-Cas9 can restore the vision and do away with the progressive degradation of view which is caused by RP (Daiger e al. 2015). Researchers need to do better on completely curing this disease and other strategies to slow down the process of degradation (Sengillo et al. 2016). We hope that the future may bring better discoveries from the laboratories in a clinical setting (Bakondi et al. 2016).

References

Bakondi, B., Lv, W., Lu, B., Jones, M. K., Tsai, Y., Kim, K. J., ... & Wang, S. (2016). In vivo CRISPR/Cas9 gene editing corrects retinal dystrophy in the S334ter-3 rat model of autosomal dominant retinitis pigmentosa. Molecular Therapy, 24(3), 556-563.

Bittner, A. K., Haythornthwaite, J. A., Patel, C., & Smith, M. T. (2018). Subjective and Objective Measures of Daytime Activity and Sleep Disturbance in Retinitis Pigmentosa. Optometry and Vision Science, 95(9), 837-843.

Cabral, T., DiCarlo, J. E., Justus, S., Sengillo, J. D., Xu, Y., & Tsang, S. H. (2017). CRISPR applications in ophthalmologic genome surgery. Current opinion in ophthalmology, 28(3), 252-259.

Daiger, S. P., Bowne, S. J., & Sullivan, L. S. (2015). Genes and mutations causing autosomal dominant retinitis pigmentosa. Cold Spring Harbor perspectives in medicine, 5(10), a017129.

Deslandes, J. Y., Giraud, M., Isidor, B., Talarmain, P., Maury, I., Marconi, S., ... & Bezieau, S. (2018). Prevalence of mutations in the PDE6B gene in autosomal recessive retinitis pigmentosa in the aim of gene therapy. Investigative Ophthalmology & Visual Science, 59(9), 38-38.

Hartong, D. T., Berson, E. L., & Dryja, T. P. (2006). Retinitis pigmentosa. The Lancet, 368(9549), 1795-1809.

Hsu, P. D., Lander, E. S., & Zhang, F. (2014). Development and applications of CRISPR-Cas9 for genome engineering. Cell, 157(6), 1262-1278.

Jones, B. W., Pfeiffer, R. L., Ferrell, W. D., Watt, C. B., Marmor, M., & Marc, R. E. (2016). Retinal remodeling in human retinitis pigmentosa. Experimental eye research, 150, 149-165.

Sengillo, J. D., Justus, S., Tsai, Y. T., Cabral, T., & Tsang, S. H. (2016, December). Gene and cellbased therapies for inherited retinal disorders: An update. In American Journal of Medical Genetics Part C: Seminars in Medical Genetics (Vol. 172, No. 4, pp. 349-366).

Vagni, P., Perlini, L. E., Parrini, M., Contestabile, A., Cancedda, L., & Ghezzi, D. (2017). Preventing visual function loss in the rd10 mouse model of retinitis pigmentosa using gene editing (No. POST_TALK).

Wu, W. H., Tsai, Y. T., Justus, S., Lee, T. T., Zhang, L., Lin, C. S., ... & Tsang, S. H. (2016). CRISPR repair reveals causative mutation in a preclinical model of retinitis pigmentosa. Molecular Therapy, 24(8), 1388-1394.

Zhong, H., Chen, Y., Li, Y., Chen, R., & Mardon, G. (2015). CRISPR-engineered mosaicism rapidly reveals that loss of Kcnj13 function in mice mimics human disease phenotypes. Scientific reports, 5, 8366.