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Genetic and physiological characteristics of CsNPR3 edited citrus and their impact on HLB tolerance.

Huanglongbing (HLB) disease, caused by Candidatus Liberibacter asiaticus (CaLas), severely impacts citrus production, and currently, there is no cure. Developing HLB-resistant or tolerant cultivars is crucial, with modifying defense-related genes being a promising approach to managing HLB. NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1) is a positive regulator of systemic acquired resistance (SAR), which enhances resistance to pathogens, whereas NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 3 (NPR3) is a negative regulator of SAR. To unambiguously address the role of CsNPR3 in HLB, we introduced mutations into the CsNPR3 gene in sweet orange (Citrus sinensis L. Osbeck) through genome editing and assessed their effects on morphology, physiology, and resistance/tolerance to HLB. Several genome-edited 'Hamlin' sweet orange trees harboring frameshift-inducing insertions or deletions were identified. After confirming the genome editing using Sanger sequencing, selected lines were grafted onto C-146 trifoliate hybrid rootstocks for clonal propagation. The progenies were then infected with CaLas using a no-choice Asian Citrus Psyllid (ACP) feeding assay. Evaluation of the genetic and physiological characteristics of CsNPR3-edited citrus trees under greenhouse conditions revealed that the edited trees exhibited greater vigor than the wild-type trees, despite the lack of significant differences in CaLas titers. Although further field evaluation is needed, our findings indicate that CsNPR3 contributes to HLB-caused tree deterioration and demonstrate that editing CsNPR3 can enhance tolerance to HLB.

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Open Access Just Published
Beyond the traditional distinctions of genome editing: evaluating a vulnerability framework.

Over 40years ago, the 1982 Splicing Life report outlined the two distinctions that have orientated much of the normative and legal landscape of genetic intervention or genome editing since - that of somatic versus germline (or heritable interventions) and medical versus non-medical (or enhancement) applications. During this time, these distinctions have been used to ethically prioritize some areas of research and potential application, such as somatic treatments, while considering others for prohibition, such as germline enhancements. Nevertheless, somatic interventions may also be done for controversial enhancement purposes while some germline interventions may be done with greater prima facie justification (e.g., the enhancement of athletic ability versus the avoidance of Tay-Sachs disease). Even with new somatic treatments that are generally lauded, exemplified with the case of Casgevy, many issues still arise - such as cost and access, particularly salient on a global level. The concerns over a dystopian future of genetic haves and have nots, as a result of enhancement and/or germline interventions, that perhaps may happen, should not distract us from a greater attention to what is happening in the here and now. In this paper, we will highlight the limits of the two distinctions in terms of moving from questions of "should a technology be used" to "how should a technology be used." We argue that an additional focus on vulnerability and marginalization can be useful to support the attempt to better prioritize which interventions should be permitted or prohibited. We show how this can better dovetail with calls for effective (global) governance and reasonable consensus by focusing on the most urgent issues and developing policy accordingly, while leaving aside more abstract issues for further discussion.

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Open Access
Targeting DLBCL by mutation-specific disruption of cancer-driving oncogenes.

Diffuse large B cell lymphomas (DLBCL) are highly aggressive tumors. Their genetic complexity and heterogeneity have hampered the development of novel approaches for precision medicine. Our study aimed to develop a personalized therapy for DLBCL by utilizing the CRISPR/Cas system to induce knockouts (KO) of driver genes, thereby causing cancer cell death while minimizing side effects. We focused on OCI-LY3 cells, modeling DLBCL, and compared them with BJAB cells as controls. Analysis of whole exome sequencing revealed significant mutations in genes like PAX5, CD79B, and MYC in OCI-LY3 cells. CRISPR/Cas9-mediated KO of these genes resulted in reduced cancer cell viability. Subsequent single and dual gRNA targeting of PAX5 mutations inhibited proliferation specifically in OCI-LY3 cells. Moreover, dual gRNA targeting of PAX5 and MYC induced chromosomal rearrangements, reducing cell proliferation substantially. However, targeting single intronic mutations did not affect cell viability, highlighting the importance of disrupting protein function. Targeting multiple mutations simultaneously addresses intra-tumoral heterogeneity, and the transient delivery of CRISPR/Cas9 allows for permanent gene disruption. While challenges such as incomplete editing efficiency and delivery limitations exist, further optimization may enhance therapeutic efficacy. Overall, our findings demonstrate the efficacy of CRISPR/Cas9 in targeting oncogenic mutations, opening avenues for precision medicine in DLBCL treatment.

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Open Access
Knockout mutation in TaD27 enhances number of productive tillers in hexaploid wheat.

Recent advances allow the deployment of cluster regularly interspaced short palindromic repeats (CRISPR)-associated endonucleases (Cas) system for the targeted mutagenesis in the genome with accuracy and precision for trait improvement in crops. CRISPR-Cas systems have been extensively utilized to induce knockout or frameshift mutations in the targeted sequence of mostly negative regulating genes for wheat improvement. However, most of the reported work has been done in non-commercial varieties of wheat and introgression of edited alleles into breeding population comes with the penalty of unwanted linkage-drag. Wheat yield is controlled by various genes such as positive and negative regulators. The TaD27 gene is described as a negative regulator of shoot branching or tillering and involved in the biosynthesis of strigolactones. In this study, we developed Tad27 knockout mutant lines of an elite wheat cultivar that showed a twofold increase in the number of tillers and 1.8-fold increase in the number of grains per plant. Subsequently, enhancing the grain yield without any morphological penalty in the architecture of the plants. The co-transformation of regeneration enhancing growth regulator, Growth Regulating Factor 4 (GRF4) and its cofactor GRF-Interacting Factor 1 (GIF1), under single T-DNA cassette improved the regeneration efficiency up to 6% of transgenic events from mature embryos of wheat. Our results indicate that the CRISPR-mediated targeted mutagenesis confers the potential to knockout yield-related negative regulators in elite cultivars of wheat that can substantially enhance grain yield per plant and this strategy can be harnessed for the improvement of future wheat.

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Open Access
The potential of HBV cure: an overview of CRISPR-mediated HBV gene disruption.

Hepatitis B virus (HBV) infection is a common cause of liver disease worldwide. The current antiviral treatment using nucleotide analogues (NAs) can only suppress de novo HBV replication but cannot eliminate chronic HBV infection due to the persistence of covalently closed circular (ccc) DNA that sustains viral replication. The CRISPR/Cas9 system is a novel genome-editing tool that enables precise gene disruption and inactivation. With high efficiency and simplicity, the CRISPR/Cas9 system has been utilized in multiple studies to disrupt the HBV genome specifically, eliciting varying anti-HBV effects both in vitro and in vivo. Additionally, multi-locus gene targeting has shown enhanced antiviral activity, paving the way for combination therapy to disrupt and inactivate HBV cccDNA as well as integrated HBV DNA. Despite its promising antiviral effects, this technology faces several challenges that need to be overcome before its clinical application, i.e., off-target effects and in vivo drug delivery. As such, there is a need for improvement in CRISPR/Cas9 efficiency, specificity, versatility, and delivery. Here, we critically review the recent literature describing the tools employed in designing guide RNAs (gRNAs) targeting HBV genomes, the vehicles used for expressing and delivering CRISPR/Cas9 components, the models used for evaluating CRISPR-mediated HBV gene disruption, the methods used for assessing antiviral and off-target effects induced by CRISPR/Cas9-mediated HBV gene disruption, and the prospects of future directions and challenges in leveraging this HBV gene-editing approach, to advance the HBV treatment toward a clinical cure.

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Open Access
Making gene editing accessible in resource limited environments: recommendations to guide a first-time user.

The designer nuclease, CRISPR-Cas9 system has advanced the field of genome engineering owing to its programmability and ease of use. The application of these molecular scissors for genome engineering earned the developing researchers the Nobel prize in Chemistry in the year 2020. At present, the potential of this technology to improve global challenges continues to grow exponentially. CRISPR-Cas9 shows promise in the recent advances made in the Global North such as the FDA-approved gene therapy for the treatment of sickle cell anaemia and β-thalassemia and the gene editing of porcine kidney for xenotransplantation into humans affected by end-stage kidney failure. Limited resources, low government investment with an allocation of 1% of gross domestic production to research and development including a shortage of skilled professionals and lack of knowledge may preclude the use of this revolutionary technology in the Global South where the countries involved have reduced science and technology budgets. Focusing on the practical application of genome engineering, successful genetic manipulation is not easily accomplishable and is influenced by the chromatin landscape of the target locus, guide RNA selection, the experimental design including the profiling of the gene edited cells, which impacts the overall outcome achieved. Our assessment primarily delves into economical approaches of performing efficient genome engineering to support the first-time user restricted by limited resources with the aim of democratizing the use of the technology across low- and middle-income countries. Here we provide a comprehensive overview on existing experimental techniques, the significance for target locus analysis and current pitfalls such as the underrepresentation of global genetic diversity. Several perspectives of genome engineering approaches are outlined, which can be adopted in a resource limited setting to enable a higher success rate of genome editing-based innovations in low- and middle-income countries.

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Open Access