Chanjuan Jiang

Hailong Wang

Qunxin She

Frontiers in Genome Editing

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Editorial: Insights in genomeediting tools and mechanisms:2022Chanjuan Jiang, Qunxin She and Hailong Wang*State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University,Qingdao, Shandong, ChinaKEYWORDSCRISPR/Cas, genome editing, peanut, Tuta absoluta, Eimeria tenella, β-thalassemiaEditorial on the Research TopicInsights in genome editing tools and mechanisms: 2022Genome editing technologies are important tools for studying the specific functions ofindividual genes or modulating the expression of important genes in organisms for biologicalresearch. CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPRassociated) is the prokaryotic adaptive immune system that protects hosts from invadingviruses and plasmids. CRISPR/Cas9 systems are the most frequently used type of genomeediting tool, which is composed of the Cas9 nuclease and the guide RNA which directsCas9 to the target DNA site by sequence complementarity. In natural systems, guide RNAsare composed of two separate RNA molecules, the CRISPR RNA (crRNA) and the trans-activating crRNA (tracrRNA), which are commonly artificially fused together to yield asingle guide RNA for genome editing (Jinek et al., 2012). In addition to CRISPR/Cas9, avariety of other CRISPR-Cas systems, such as CRISPR/Cas12a (Cpf1), have been developedto overcome the difficulties of genome editing at different loci in different organisms.Recently, several new CRISPR/Cas systems have been identified and employed for genomeediting, some of which are bacteriophage origin (Al-Shayeb et al., 2022). In addition, effortshave continuously been made to optimize genome editing efficiency by different CRISPR/Cas systems belonging to all six known types. Furthermore, CRISPR/Cas9 systems have beenoptimized for reducing their toxicity and for boosting knock-in efficiency in genome editingof primary human cells by using long single-stranded DNA homology-directed repairtemplates with short regions of double-stranded DNA containing Cas9 target sequences onboth ends (Shy et al., 2023). This Research Topic is aimed to further explore the applicationof CRISPR/Cas genome editing tools in more biological systems and it includes four researcharticles. Three articles are under the category of Original Research, and one belongs to theBrief Research Report.Peanut (Arachis hypogaea L.) seeds are the source of our daily edible oil and are rich inmonounsaturated oleic acid and polyunsaturated linoleic acid. Fatty Acid Desaturase 2(FAD2) catalyzes the conversion of oleic acid to linoleic acid. Compared with linoleic acid,oleic acid has better oxidative stability and health benefits, but increasing oleic acid contentby knocking out the FAD2 gene can lead to poor plant stress tolerance. The RY repeatelement and 2S seed protein motif cis-regulatory elements in the 5′UTR of FAD2 genes havebeen suggested to have enhancer activity. Neelakandan et al. targeted these two cis-regulatory elements of the FAD2 gene promoter by CRISPR/Cas9 to downregulate theexpression levels of two homologous FAD2 genes in seed while maintaining normalOPEN ACCESSEDITED AND REVIEWED BYScott Bailey,Johns Hopkins University, United States*CORRESPONDENCEHailong Wang,wanghailong@sdu.edu.cnRECEIVED 15 June 2023ACCEPTED 05 July 2023PUBLISHED 11 July 2023CITATIONJiang C, She Q and Wang H (2023),Editorial: Insights in genome editing toolsand mechanisms: 2022.Front. Genome Ed. 5:1240576.doi: 10.3389/fgeed.2023.1240576COPYRIGHT© 2023 Jiang, She and Wang. This is anopen-access article distributed under theterms of the Creative CommonsAttribution License (CC BY). The use,distribution or reproduction in otherforums is permitted, provided the originalauthor(s) and the copyright owner(s) arecredited and that the original publicationin this journal is cited, in accordance withaccepted academic practice. No use,distribution or reproduction is permittedwhich does not comply with these terms.Frontiers in Genome Editing frontiersin.org01TYPE EditorialPUBLISHED 11 July 2023DOI 10.3389/fgeed.2023.1240576regulation in other plant tissues. Oleic acid content increased by55%–70% in seeds of the edited RY motif and 55%–60% in seeds ofthe edited 2S motif compared with the wild-type seeds. The use ofCRISPR/Cas9 based promoter or enhancer editing will accelerate thepace of cultivar development without introducing potentiallydeleterious alleles and linkage drag.The tomato leaf miner Tuta absoluta (Meyrick), which isresistant to many pesticides, is one of the most destructivetomato pests in the world. To control the tomato leaf miner,intensive research on this species has been required. However,the lack of effective genome editing tools has prevented furtherfunctional genomic studies of the tomato leaf miner. Ji et al.demonstrated for the first time that CRISPR/Cas can be used forgenome editing in T. absoluta. The CRISPR/Cas9 zygotemicroinjection protocol for generating heritable mutations in T.absoluta was developed. The injection of fertilized eggs withCas9 protein and four sgRNAs, which targeted cinnabar exon 3,resulted in a mutagenesis rate of 31.9% for eggs reaching adulthood.The comprehensive and detailed CRISPR/Cas9 workflow for theefficient genome editing of T. absoluta will greatly facilitate thediscovery of suitable RNAi (RNA interference) control targets andthe subsequent development of novel control strategies.Eimeria species can cause coccidiosis in poultry and causesignificant economic losses to the poultry industry. Genomeediting of Eimeria is of great importance for the development ofvaccines and drugs. Although CRISPR/Cas9 has been used to edit thegenome of Eimeria tenella (E. tenella), it requires plasmids to expressCRISPR/Cas9 and would introduce transgenes, which largely limitsthe application in vaccine development (Hu et al., 2020; Tang et al.,2020). Cheng et al. optimized the transfection conditions for theparasite E. tenella and used the optimized conditions to transform theFnCas12a protein and crRNA for modification of the EtHistone H4gene and the EtActin gene. The efficiency of FnCas12a-crRNAribonucleoprotein genome editing in E. tenella was 1.2%, whichwas lower than that (2%) obtained by integrating the Cas9 gene inthe genome. However, the FnCas12a-crRNA method based onribonucleoprotein transfection can avoid DNA contamination andwill be advantageous for vaccines development.β-thalassemia is a common monogenic disorder with an annualincidence of one in 100,000 worldwide. Lu et al. proposed a novelCas9/AV6-mediated genome editing strategy for the treatment of β-thalassemia. They mimicked natural HPFH (Hereditary persistenceof fetal hemoglobin) mutations −113A > G, −114C > T, −117G >A, −175T > C, −195C > G, and −198T > C by delivery of anAAV6 homology repair template, followed by immediateelectroporation of Cas9-ribonucleoprotein (RNP) complexesspecific to the BCL11A binding site and then successfully testedthis system in both HUDEP-2 cells and HSPCs from β-thalassemiamajor patients. They demonstrated that introducing six specificHPFH mutations leads to significant re-activation of γ-globin andthus elevates fetal hemoglobin in both HUDEP-2 cells and HSPCsderived from β-thalassemia major patients. These findings mayfacilitate the clinical transformation of genome editing-basedtreatment of hemoglobinopathies.CRISPR/Cas system has become the main driving force of thelife science revolution in the 21st century due to its advantages ingenome editing and regulation, such as low cost, stable efficiency,easy programming, and multiplex editing. However, while theCRISPR/Cas systems have great potential for genome editing,challenges remain in addressing its delivery methods, off-targetactivity, and inefficiencies in many organisms. With the rapiddevelopment of CRISPR/Cas tools, they will be continuouslyexpanded in different organisms or cells to continuously meetthe needs of basic biology research, gene therapy, biologybreeding, and other fields.Author contributionsCJ and HW wrote the editorial. QS reviewed the editorial. Allauthors contributed to the article and approved the submittedversion.AcknowledgmentsWe would like to thank all the authors that contributed to thisResearch Topic.Conflict of interestThe authors declare that the research was conducted in theabsence of any commercial or financial relationships that could beconstrued as a potential conflict of interest.Publisher’s noteAll claims expressed in this article are solely those of the authorsand do not necessarily represent those of their affiliated organizations,or those of the publisher, the editors and the reviewers. Any productthat may be evaluated in this article, or claim that may be made by itsmanufacturer, is not guaranteed or endorsed by the publisher.ReferencesAl-Shayeb, B., Skopintsev, P., Soczek, K. M., Stahl, E. C., Li, Z., Groover, E., et al.(2022). Diverse virus-encoded CRISPR-Cas systems include streamlined genomeeditors. Cell 185 (24), 4574–4586e16. doi:10.1016/j.cell.2022.10.020Hu, D., Tang, X., Ben Mamoun, C., Wang, C., Wang, S., Gu, X., et al. (2020). Efficientsingle-gene and gene family editing in the apicomplexan parasite Eimeria tenella usingCRISPR-cas9. Front. Bioeng. Biotechnol. 8, 128. doi:10.3389/fbioe.2020.00128Jinek, M., Chylinski, K., Fonfara, I., Hauer, M., Doudna, J. A., andCharpentier, E. (2012). A programmable dual-RNA-guided DNAendonuclease in adaptive bacterial immunity. Science 337 (6096), 816–821.doi:10.1126/science.1225829Shy, B. R., Vykunta, V. S., Ha, A., Talbot, A., Roth, T. L., Nguyen, D. N., et al. (2023). High-yield genome engineering in primary cells using a hybrid ssDNA repair template and small-molecule cocktails. Nat. Biotechnol. 41 (4), 521–531. doi:10.1038/s41587-022-01418-8Tang, X., Suo, J., Liang, L., Duan, C., Hu, D., Gu, X., et al. (2020). Genetic modificationof the protozoan Eimeria tenella using the CRISPR/Cas9 system. Vet. Res. 51 (1), 41.doi:10.1186/s13567-020-00766-0Frontiers in Genome Editing frontiersin.org02Jiang et al. 10.3389/fgeed.2023.1240576

Editorial: Insights in genome editing tools and mechanisms: 2022

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Editorial: Insights in genome editing tools and mechanisms: 2022

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