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A new era of gene editing for the treatment of human diseases.
Kc, M, Steer, CJ
Swiss medical weekly. 2019;:w20021
Abstract
The treatment of human diseases using gene-editing technology has been envisioned for several decades with the realisation that so many were associated with mutations in DNA. The Human Genome Project opened new doors for identifying the genetic bases for human suffering. Research on gene editing has been active since the 1970s, but the technology has seen substantial growth and application just within the past decade. Simply stated, CRISPR technology has become a phenomenon in both biomedical and therapeutics research. Concurrently, cell therapies and pluripotent stem cell research have also been refined and now interfaced with CRISPR technology to enhance and maximise their potential in modelling as well as treatment of human diseases. In this review, we discuss the novel and revolutionary modality of gene editing, as this marks a new era in research and medicine. We also discuss gene-modifying technologies leading to CRISPR, as they are still being used for a wide variety of genomic applications. The modes and challenges for delivery of gene editing components are also discussed. Lastly, we review examples of human diseases that are not only amenable to gene editing techniques, but also show true promise of cure in the early 21st century of genetic correction and gene repair.
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2.
Gene-function studies in systemic lupus erythematosus.
Rosetti, F, de la Cruz, A, Crispín, JC
Current opinion in rheumatology. 2019;(2):185-192
Abstract
PURPOSE OF REVIEW The aim of this review is to discuss recent developments in our understanding of how systemic lupus erythematosus (SLE)-associated genes contribute to autoimmunity. RECENT FINDINGS Gene-function studies have revealed mechanisms through which SLE-associated alleles of IFIH1, TNFAIP3, IRF5, and PRDM1 likely contribute to the development of autoimmunity. Novel research has identified Mac-1 (encoded by ITGAM), CaMK4, and iRhom2 as plausible therapeutic targets in lupus nephritis. SUMMARY The work discussed in this review has broad implications for our understanding of the pathogenesis of SLE and for the development of novel therapeutic strategies.
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3.
CRISPR/Cas9 technology as a potent molecular tool for gene therapy.
Karimian, A, Azizian, K, Parsian, H, Rafieian, S, Shafiei-Irannejad, V, Kheyrollah, M, Yousefi, M, Majidinia, M, Yousefi, B
Journal of cellular physiology. 2019;(8):12267-12277
Abstract
Clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease 9 (CRISPR-Cas9) is an RNA-guided gene editing tool which offers several advantageous characteristics in comparison with the conventional methods (e.g., zinc finger nucleases and transcription activator-like effector nucleases) such as cost-effectiveness, flexibility, and being easy-to-use. Despite some limitations such as efficient delivery and safety, CRISPR-Cas9 is still the most convenient tool for gene editing purposes. Due to the potential capability of the CRISPR-Cas9 system in genome editing and correction of casual mutations, it can be considered as a possible therapeutic system in the treatment of disorders associated with the genome mutations and in particular cancer treatment. In this review, we will discuss CRISPR-Cas-based gene editing along with its classifications and mechanism of action. Furthermore, the therapeutic application of the CRISPR-Cas9 system in mutational disorders, delivery systems, as well as its advantages and limitations with a special emphasis on cancer treatment will be discussed.
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4.
Recent Progress in Gene Therapy and Other Targeted Therapeutic Approaches for Beta Thalassemia.
Hamed, EM, Meabed, MH, Aly, UF, Hussein, RRS
Current drug targets. 2019;(16):1603-1623
Abstract
Beta-thalassemia is a genetic disorder characterized by the impaired synthesis of the betaglobin chain of adult hemoglobin. The disorder has a complex pathophysiology that affects multiple organ systems. The main complications of beta thalassemia are ineffective erythropoiesis, chronic hemolytic anemia and hemosiderosis-induced organ dysfunction. Regular blood transfusions are the main therapy for beta thalassemia major; however, this treatment can cause cardiac and hepatic hemosiderosis - the most common cause of death in these patients. This review focuses on unique future therapeutic interventions for thalassemia that reverse splenomegaly, reduce transfusion frequency, decrease iron toxicity in organs, and correct chronic anemia. The targeted effective protocols include hemoglobin fetal inducers, ineffective erythropoiesis correctors, antioxidants, vitamins, and natural products. Resveratrol is a new herbal therapeutic approach which serves as fetal Hb inducer in beta thalassemia. Hematopoietic stem cell transplantation (HSCT) is the only curative therapy for beta thalassemia major and is preferred over iron chelation and blood transfusion for ensuring long life in these patients. Meanwhile, several molecular therapies, such as ActRIIB/IgG1 Fc recombinant protein, have emerged to address complications of beta thalassemia or the adverse effects of current drugs. Regarding gene correction strategies, a phase III trial called HGB-207 (Northstar-2; NCT02906202) is evaluating the efficacy and safety of autologous cell transplantation with LentiGlobin. Advanced gene-editing approaches aim to cut DNA at a targeted site and convert HbF to HbA during infancy, such as the suppression of BCL11A (B cell lymphoma 11A), HPFH (hereditary persistence of fetal hemoglobin) and zinc-finger nucleases. Gene therapy is progressing rapidly, with multiple clinical trials being conducted in many countries and the promise of commercial products to be available in the near future.
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The Location of Exon 4 Mutations in RP1 Raises Challenges for Genetic Counseling and Gene Therapy.
Nanda, A, McClements, ME, Clouston, P, Shanks, ME, MacLaren, RE
American journal of ophthalmology. 2019;:23-29
Abstract
PURPOSE Mutations in the photoreceptor gene RP1 lead to recessive or dominantly inherited retinitis pigmentosa (RP). Since the dominantly inherited phenotype is generally milder than recessive cases, it raises the possibility that it could arise by haploinsufficiency; however, most mutations are in the terminal exon 4, which would be predicted to generate truncated proteins. We therefore assessed a cohort of RP patients with confirmed mutations in RP1 to examine the genetic basis of the exon 4 mutations. DESIGN Observational case series. METHODS A retrospective review of 15 patients, aged between 36 and 84, with RP1 mutations in exon 4 confirmed by Sanger sequencing. All patients underwent full ophthalmic examination. RESULTS Two patients had homozygous mutations in RP1, p.(Glu1526*) and p.(Ser486fs), and presented with severe early-onset retinal degeneration. Their first-degree relatives were unaffected. Thirteen patients had dominantly inherited RP presenting in adult life with a rod-cone dystrophy phenotype. Four novel mutations were identified. All mutations were predicted to produce truncated RP1 protein of variable lengths, as follows: p.(Arg677*), p.(Gln679*), p.(Leu722*), p.(Ile725Argfs*6), p.(Ser734*)x2, p.(Leu762Tyrfs*17)x2, p.(Leu866Lysfs*7)x2, p.(Arg872Thrfs*2)x2, and p.(Gln917*). CONCLUSION The RP1 protein with a predicted length between 677 and 917 amino acids seems to have a dominant negative effect, whereas proteins shorter (486 amino acids) or longer than this (1526 amino acids) lead to a more severe phenotype, but only in homozygous individuals. Since mutations at various points along exon 4 have divergent consequences, genetic testing alone may be insufficient for counseling, but recessive inheritance should be considered likely in severe early-onset cases.
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Efficacy, Safety, and Durability of Voretigene Neparvovec-rzyl in RPE65 Mutation-Associated Inherited Retinal Dystrophy: Results of Phase 1 and 3 Trials.
Maguire, AM, Russell, S, Wellman, JA, Chung, DC, Yu, ZF, Tillman, A, Wittes, J, Pappas, J, Elci, O, Marshall, KA, et al
Ophthalmology. 2019;(9):1273-1285
Abstract
PURPOSE To report the durability of voretigene neparvovec-rzyl (VN) adeno-associated viral vector-based gene therapy for RPE65 mutation-associated inherited retinal dystrophy (IRD), including results of a phase 1 follow-on study at year 4 and phase 3 study at year 2. DESIGN Open-label phase 1 follow-on clinical trial and open-label, randomized, controlled phase 3 clinical trial. PARTICIPANTS Forty subjects who received 1.5×1011 vector genomes (vg) of VN per eye in at least 1 eye during the trials, including 11 phase 1 follow-on subjects and 29 phase 3 subjects (20 original intervention [OI] and 9 control/intervention [CI]). METHODS Subretinal injection of VN in the second eye of phase 1 follow-on subjects and in both eyes of phase 3 subjects. MAIN OUTCOME MEASURES End points common to the phase 1 and phase 3 studies included change in performance on the Multi-Luminance Mobility Test (MLMT) within the illuminance range evaluated, full-field light sensitivity threshold (FST) testing, and best-corrected visual acuity (BCVA). Safety end points included adverse event reporting, ophthalmic examination, physical examination, and laboratory testing. RESULTS Mean (standard deviation) MLMT lux score change was 2.4 (1.3) at 4 years compared with 2.6 (1.6) at 1 year after administration in phase 1 follow-on subjects (n = 8), 1.9 (1.1) at 2 years, and 1.9 (1.0) at 1 year post-administration in OI subjects (n = 20), and 2.1 (1.6) at 1 year post-administration in CI subjects (n = 9). All 3 groups maintained an average improvement in FST, reflecting more than a 2 log10(cd.s/m2) improvement in light sensitivity at 1 year and subsequent available follow-up visits. The safety profile was consistent with vitrectomy and the subretinal injection procedure, and no deleterious immune responses occurred. CONCLUSIONS After VN gene augmentation therapy, there was a favorable benefit-to-risk profile with similar improvement demonstrated in navigational ability and light sensitivity among 3 groups of subjects with RPE65 mutation-associated IRD, a degenerative disease that progresses to complete blindness. The safety profile is consistent with the administration procedure. These data suggest that this effect, which is nearly maximal by 30 days after VN administration, is durable for 4 years, with observation ongoing.
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7.
Non-Viral Delivery To Enable Genome Editing.
Rui, Y, Wilson, DR, Green, JJ
Trends in biotechnology. 2019;(3):281-293
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Abstract
Genome-editing technologies such as zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENS), and the clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein system have revolutionized biological research. Each biotechnology consists of a DNA-binding protein that can be programmed to recognize and initiate double-strand breaks (DSBs) for site-specific gene modification. These technologies have the potential to be harnessed to cure diseases caused by aberrant gene expression. To be successful therapeutically, their functionality depends on their safe and efficient delivery into the cell nucleus. This review discusses the challenges in the delivery of genome-editing tools, and highlights recent innovations in non-viral delivery that have potential to overcome these limitations and advance the translation of genome editing towards patient care.
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Future of human mitochondrial DNA editing technologies.
Verechshagina, N, Nikitchina, N, Yamada, Y, Harashima, Н, Tanaka, M, Orishchenko, K, Mazunin, I
Mitochondrial DNA. Part A, DNA mapping, sequencing, and analysis. 2019;(2):214-221
Abstract
ATP and other metabolites, which are necessary for the development, maintenance, and functioning of bodily cells are all synthesized in the mitochondria. Multiple copies of the genome, present within the mitochondria, together with its maternal inheritance, determine the clinical manifestation and spreading of mutations in mitochondrial DNA (mtDNA). The main obstacle in the way of thorough understanding of mitochondrial biology and the development of gene therapy methods for mitochondrial diseases is the absence of systems that allow to directly change mtDNA sequence. Here, we discuss existing methods of manipulating the level of mtDNA heteroplasmy, as well as the latest systems, that could be used in the future as tools for human mitochondrial genome editing.
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Motivations and Decision Making Processes of Men With X-linked Retinoschisis Considering Participation in an Ocular Gene Therapy Trial.
Turriff, A, Blain, D, Similuk, M, Biesecker, B, Wiley, H, Cukras, C, Sieving, PA
American journal of ophthalmology. 2019;:90-96
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Abstract
PURPOSE To describe the motivations, expectations, and other factors men with X-linked retinoschisis (XLRS) consider when making decisions to participate in an early phase ocular gene therapy clinical trial. DESIGN Qualitative interview study. METHODS Men with XLRS who were considering participation in a phase I/IIa ocular gene therapy clinical trial at the National Eye Institute were eligible for this study. Trial participants (n = 9) were interviewed prior to receiving the gene transfer and then at 3 and 12 months later. Trial participation decliners (n = 2) were interviewed at an initial visit and 12 months later. Those screened for the trial and found ineligible (n = 2) were interviewed at an initial visit only. Interviews were transcribed, coded, and analyzed thematically. RESULTS Interview participants described decision making factors as risk-benefit assessments, personal intuition, trust in the study team, and religious faith. Altruism and the potential for therapeutic benefit were the main motives for trial participation, whereas the uncertainty of risks and benefits was the reason 2 men declined participation. Although most participants hoped for direct benefit, no one expected to benefit. Almost all interview participants considered their decision straightforward and were satisfied with their decision when interviewed over time. Meaningful relationships with the study team and perceived secondary benefits to participation contributed to positive trial experiences. CONCLUSIONS Engaging prospective research participants in a discussion about their hopes, expectations, and personal factors provides a more complete understanding of patient decision making and may help support informed choices to participate in clinical trials for XLRS.
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Attenuation of Inherited and Acquired Retinal Degeneration Progression with Gene-based Techniques.
Cho, GY, Bolo, K, Park, KS, Sengillo, JD, Tsang, SH
Molecular diagnosis & therapy. 2019;(1):113-120
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Abstract
Inherited retinal dystrophies cause progressive vision loss and are major contributors to blindness worldwide. Advances in gene therapy have brought molecular approaches into the realm of clinical trials for these incurable illnesses. Select phase I, II and III trials are complete and provide some promise in terms of functional outcomes and safety, although questions do remain over the durability of their effects and the prevalence of inflammatory reactions. This article reviews gene therapy as it can be applied to inherited retinal dystrophies, provides an update of results from recent clinical trials, and discusses the future prospects of gene therapy and genome surgery.