CRISPR/Cas9-Mediated Genome Editing as a Therapeutic Approach for Leber Congenital Amaurosis 10

CRISPR targeting of mmu-miR-21a through a single adeno-associated virus vector prolongs survival of glioblastoma-bearing mice

Glioblastoma (GB), the most aggressive tumor of the central nervous system (CNS), has poor patient outcomes with limited effective treatments available. MicroRNA-21 (miR-21(a)) is a known oncogene, abundantly expressed in many cancer types. miR-21(a) promotes GB progression, and lack of miR-21(a) reduces the tumorigenic potential. Here, we propose a single adeno-associated virus (AAV) vector strategy targeting mmu-miR-21a using the Staphylococcus aureus Cas9 ortholog (SaCas9) guided by a single-guide RNA (sgRNA). Our results demonstrate that AAV8 is a well-suited AAV serotype to express SaCas9-KKH/sgRNA at the tumor site in an orthotopic GB model. The SaCas9-KKH induced a genomic deletion, resulting in lowered mmu-miR-21a levels in the brain, leading to reduced tumor growth and improved overall survival. In this study, we demonstrated that disruption of genomic mmu-miR-21a with a single AAV vector influenced glioma development, resulting in beneficial anti-tumor outcomes in GB-bearing mice.

Advances in retina genetics: Progress, potential, and challenges

The field of retinal genetics has seen remarkable advancements lately, reshaping our understanding of various retinal conditions, including age-related macular degeneration, diabetic retinopathy, and inherited retinal dystrophies. The purpose of this review is to provide an overview of the current status of genetics in the retina, covering the progress made, the expected future developments, and the challenges yet to be overcome. We highlight key advancements such as the advent of next-generation sequencing, which has exponentially enhanced the discovery of genetic mutations, thus also enabling personalized medicine/therapeutic approaches. Stem cells, gene augmentation, and gene-editing techniques such as CRISPR/Cas9 are discussed, in which we highlight ongoing research as well as their potential in the targeted treatment of retinal diseases. Despite these promising advancements, the field faces significant challenges, such as the complex interpretation of genetic data, ethical considerations, and the translational gap from bench to bedside. This review serves as a comprehensive guide not only to ophthalmologists but also to other healthcare professionals, scientists, and policymakers, providing insights into the rapidly evolving landscape of retinal genetics. It aims to stimulate further research and collaboration to surmount existing challenges and harness the full potential of genetic advancements for retinal health.

Haplotype editing with CRISPR/Cas9 as a therapeutic approach for dominant-negative missense mutations in NEFL

Inactivation of disease alleles by allele-specific editing is a promising approach to treat dominant-negative genetic disorders, provided the causative gene is haplo-sufficient. We previously edited a dominant NEFL missense mutation with inactivating frameshifts and rescued disease-relevant phenotypes in induced pluripotent stem cell (iPSC)-derived motor neurons. However, a multitude of different NEFL missense mutations cause disease. Here, we addressed this challenge by targeting common single-nucleotide polymorphisms in cis with NEFL disease mutations for gene excision. We validated this haplotype editing approach for two different missense mutations and demonstrated its therapeutic potential in iPSC-motor neurons. Surprisingly, our analysis revealed that gene inversion, a frequent byproduct of excision editing, failed to reliably disrupt mutant allele expression. We deployed alternative strategies and novel molecular assays to increase therapeutic editing outcomes while maintaining specificity for the mutant allele. Finally, population genetics analysis demonstrated the power of haplotype editing to enable therapeutic development for the greatest number of patients. Our data serve as an important case study for many dominant genetic disorders amenable to this approach.

Recombinant adeno-associated virus as a delivery platform for ocular gene therapy: A comprehensive review

Adeno-associated virus (AAV) has emerged as a leading platform for in vivo gene therapy, particularly in ocular diseases. AAV-based therapies are characterized by low pathogenicity and broad tissue tropism and have demonstrated clinical success, as exemplified by voretigene neparvovec-rzyl (Luxturna) being the first gene therapy to be approved by the U.S. Food and Drug Administration to treat RPE65-associated Leber congenital amaurosis (LCA). However, several challenges remain in the development of AAV-based gene therapies, including immune responses, limited cargo capacity, and the need for enhanced transduction efficiency, especially for intravitreal delivery to photoreceptors and retinal pigment epithelium cells. This review explores the biology of AAVs in the context of gene therapy, innovations in capsid engineering, and clinical advancements in AAV-based ocular gene therapy. We highlight ongoing clinical trials targeting inherited retinal diseases and acquired conditions, discuss immune-related limitations, and examine novel strategies for enhancing AAV vector performance to address current barriers.

Insights on the Genetic and Phenotypic Complexities of Optic Neuropathies

Background/Objectives: Optic neuropathies are a category of illnesses that ultimately cause damage to the optic nerve, leading to vision impairment and possible blindness. Disorders such as dominant optic atrophy (DOA), Leber hereditary optic neuropathy (LHON), and glaucoma demonstrate intricate genetic foundations and varied phenotypic manifestations. This narrative review study seeks to consolidate existing knowledge on the genetic and molecular mechanisms underlying ocular neuropathies, examine genotype-phenotype correlations, and assess novel therapeutic options to improve diagnostic and treatment methodologies. Methods: A systematic literature review was performed in October 2024, utilizing PubMed, Medline, the Cochrane Library, and ClinicalTrials.gov. Search terms encompassed "optic neuropathy", "genetic variants", "LHON", "DOA", "glaucoma", and "molecular therapies". Studies were chosen according to established inclusion criteria, concentrating on the genetic and molecular dimensions of optic neuropathies and their therapeutic ramifications. Results: The results indicate that DOA and LHON are mostly associated with the mitochondrial dysfunction resulting from pathogenic variants in nuclear genes, mainly OPA1, and mitochondrial DNA (mtDNA) genes, respectively. Glaucoma, especially its intricate variants, is linked to variants in genes like MYOC, OPTN, and TBK1. Molecular mechanisms, such as oxidative stress and inflammatory modulation, are pivotal in disease progression. Innovative therapeutics, including gene therapy, RNA-based treatments, and antioxidants such as idebenone, exhibit promise for alleviating optic nerve damage and safeguarding vision. Conclusions: Genetic and molecular investigations have markedly enhanced our comprehension of ocular neuropathies. The amalgamation of genetic and phenotypic data is essential for customized medical strategies. Additional research is required to enhance therapeutic strategies and fill the gaps in our understanding of the underlying pathophysiology. This interdisciplinary approach shows potential for enhancing patient outcomes in ocular neuropathies.

Infantile Nystagmus Syndrome-Associated Inherited Retinal Diseases: Perspectives from Gene Therapy Clinical Trials

Inherited retinal diseases (IRDs) are a clinically and genetically diverse group of progressive degenerative disorders that can result in severe visual impairment or complete blindness. Despite their predominantly monogenic inheritance patterns, the genetic complexity of over 300 identified disease-causing genes presents a significant challenge in correlating clinical phenotypes with genotypes. Achieving a molecular diagnosis is crucial for providing patients with definitive diagnostic clarity and facilitating access to emerging gene-based therapies and ongoing clinical trials. Recent advances in next-generation sequencing technologies have markedly enhanced our ability to identify genes and genetic defects leading to IRDs, thereby propelling the development of gene-based therapies. The clinical success of voretigene neparvovec (Luxturna), the first approved retinal gene therapy for RPE65-associated Leber congenital amaurosis (LCA), has spurred considerable research and development in gene-based therapies, highlighting the importance of reviewing the current status of gene therapy for IRDs, particularly those utilizing adeno-associated virus (AAV)-based therapies. As novel disease-causing mutations continue to be discovered and more targeted gene therapies are developed, integrating these treatment opportunities into the standard care for IRD patients becomes increasingly critical. This review provides an update on the diverse phenotypic-genotypic landscape of IRDs, with a specific focus on recent advances in the understanding of IRDs in children with infantile nystagmus syndrome (INS). We highlight the complexities of the genotypic-phenotypic landscape of INS-associated IRDs, including conditions such as achromatopsia, LCA, congenital stationary night blindness, and subtypes of retinitis pigmentosa. Additionally, we provide an updated overview of AAV-based gene therapies for these diseases and discuss the potential of gene-based therapies for underlying IRDs that lead to INS, offering a valuable resource for pediatric patients potentially eligible for ongoing clinical trials.

Lipid nanoparticle technology-mediated therapeutic gene manipulation in the eyes

Millions of people worldwide have hereditary genetic disorders, trauma, infectious diseases, or cancer of the eyes, and many of these eye diseases lead to irreversible blindness, which is a major public health burden. The eye is a relatively small and immune-privileged organ. The use of nucleic acid-based drugs to manipulate malfunctioning genes that target the root of ocular diseases is regarded as a therapeutic approach with great promise. However, there are still some challenges for utilizing nucleic acid therapeutics in vivo because of certain unfavorable characteristics, such as instability, biological carrier-dependent cellular uptake, short pharmacokinetic profiles in vivo (RNA), and on-target and off-target side effects (DNA). The development of lipid nanoparticles (LNPs) as gene vehicles is revolutionary progress that has contributed the clinical application of nucleic acid therapeutics. LNPs have the capability to entrap and transport various genetic materials such as small interfering RNA, mRNA, DNA, and gene editing complexes. This opens up avenues for addressing ocular diseases through the suppression of pathogenic genes, the expression of therapeutic proteins, or the correction of genetic defects. Here, we delve into the cutting-edge LNP technology for ocular gene therapy, encompassing formulation designs, preclinical development, and clinical translation.

Publication trends of Leber congenital amaurosis researches: a bibliometric study during 2002-2022

AIM

To analyze the changes in scientific output relating to Leber congenital amaurosis (LCA) and forecast the study trends in this field.

METHODS

All of the publications in the field of LCA from 2002 to 2022 were collected from Web of Science (WOS) database. We analyzed the quantity (number of publications), quality (citation and H-index) and development trends (relative research interest, RRI) of published LCA research over the last two decades. Moreover, VOSviewer software was applied to define the co-occurrence network of keywords in this field.

RESULTS

A total of 2158 publications were ultimately examined. We found that the focus on LCA kept rising and peaked in 2015 and 2018, which is consistent with the development trend of gene therapy. The USA has contributed most to this field with 1162 publications, 56 674 citations and the highest H-index value (116). The keywords analysis was divided into five clusters to show the hotspots in the field of LCA, namely mechanism-related, genotype-related, local phenotype-related, system phenotype-related, and therapy-related. We also identified gene therapy and anti-retinal degeneration therapy as a major focus in recent years.

CONCLUSION

Our study illustrates historical research process and future development trends in LCA field. This may help to guide the orientation for further clinical diagnosis, treatment and scientific research.

Recent progress in CRISPR/Cas9 system for eye disorders

Ocular disorders encompass a broad spectrum of phenotypic and clinical symptoms resulting from several genetic variants and environmental factors. The unique anatomy and physiology of the eye facilitate validation of cutting-edge gene editing treatments. Genome editing developments have allowed researchers to treat a variety of diseases, including ocular disorders. The clustered regularly interspaced short palindromic repeats (CRISPR/Cas9) system holds considerable promise for therapeutic applications in the field of ophthalmology, including repair of aberrant genes and treatment of retinal illnesses related to the genome or epigenome. Application of CRISPR/Cas9 systems to the study of ocular disease and visual sciences have yielded innovations including correction of harmful mutations in patient-derived cells and gene modifications in several mammalian models of eye development and disease. In this study, we discuss the generation of several ocular disease models in mammalian cell lines and in vivo systems using a CRISPR/Cas9 system. We also provide an overview of current uses of CRISPR/Cas9 technologies for the treatment of ocular pathologies, as well as future challenges.

CRISPR technology in human diseases

Gene editing is a growing gene engineering technique that allows accurate editing of a broad spectrum of gene-regulated diseases to achieve curative treatment and also has the potential to be used as an adjunct to the conventional treatment of diseases. Gene editing technology, mainly based on clustered regularly interspaced palindromic repeats (CRISPR)-CRISPR-associated protein systems, which is capable of generating genetic modifications in somatic cells, provides a promising new strategy for gene therapy for a wide range of human diseases. Currently, gene editing technology shows great application prospects in a variety of human diseases, not only in therapeutic potential but also in the construction of animal models of human diseases. This paper describes the application of gene editing technology in hematological diseases, solid tumors, immune disorders, ophthalmological diseases, and metabolic diseases; focuses on the therapeutic strategies of gene editing technology in sickle cell disease; provides an overview of the role of gene editing technology in the construction of animal models of human diseases; and discusses the limitations of gene editing technology in the treatment of diseases, which is intended to provide an important reference for the applications of gene editing technology in the human disease.

A review on molecular scissoring with CRISPR/Cas9 genome editing technology

Genome editing is a technology to make specific changes in the DNA of a cell or an organism. It has significantly altered the landscape of life sciences, facilitating the establishment of exceedingly customized genetic modifications. Among various genome editing technologies, the CRISPR/Cas9 system, a specific endonuclease induces a double stranded DNA break and enabling modifications to the genome, has surfaced as a formidable and adaptable instrument. Its significance cannot be overstated, as it not only allows for the manipulation of genomes in model organisms but also holds great potential for revolutionary advances in medicine, particularly in treating genetic diseases. This review paper explores the remarkable journey of CRISPR/Cas9, its natural function, mechanisms, and transformative impact on genome editing and finally the use of artificial intelligence and other intelligent manufacturing tools used. The introduction provides the background on genome editing, emphasizing the emergence and significance of CRISPR/Cas9. Subsequent sections comprehensively elucidate its natural function, disease modeling, agriculture, and biotechnology, address therapeutic applications, and ongoing clinical trials while also discussing prospects and ethical implications. We summarized the key findings, indicating that CRISPR/Cas9 has empowered the creation of disease-specific animal models. This provides invaluable insights into pathogenic mechanisms and opens new avenues for drug discovery, reaffirming the transformative impact of CRISPR/Cas9 on genome editing. Finally we discussed the importance of continued research and collaboration for comprehensive utilization of the inherent capabilities of this molecular precision tool in shaping forthcoming advancements.

Nanoplatform-Based In Vivo Gene Delivery Systems for Cancer Therapy

Gene therapy uses modern molecular biology methods to repair disease-causing genes. As a burgeoning therapeutic, it has been widely applied for cancer therapy. Since 1989, there have been numerous clinical gene therapy cases worldwide. However, a few are successful. The main challenge of clinical gene therapy is the lack of efficient and safe vectors. Although viral vectors show high transfection efficiency, their application is still limited by immune rejection and packaging capacity. Therefore, the development of non-viral vectors is overwhelming. Nanoplatform-based non-viral vectors become a hotspot in gene therapy. The reasons are mainly as follows. 1) Non-viral vectors can be engineered to be uptaken by specific types of cells or tissues, providing effective targeting capability. 2) Non-viral vectors can protect goods that need to be delivered from degradation. 3) Nanoparticles can transport large-sized cargo such as CRISPR/Cas9 plasmids and nucleoprotein complexes. 4) Nanoparticles are highly biosafe, and they are not mutagenic in themselves compared to viral vectors. 5) Nanoparticles are easy to scale preparation, which is conducive to clinical conversion and application. Here, an overview of the categories of nanoplatform-based non-viral gene vectors, the limitations on their development, and their applications in cancer therapy.

Pluripotent stem cell-derived models of retinal disease: Elucidating pathogenesis, evaluating novel treatments, and estimating toxicity

Blindness poses a growing global challenge, with approximately 26% of cases attributed to degenerative retinal diseases. While gene therapy, optogenetic tools, photosensitive switches, and retinal prostheses offer hope for vision restoration, these high-cost therapies will benefit few patients. Understanding retinal diseases is therefore key to advance effective treatments, requiring in vitro models replicating pathology and allowing quantitative assessments for drug discovery. Pluripotent stem cells (PSCs) provide a unique solution given their limitless supply and ability to differentiate into light-responsive retinal tissues encompassing all cell types. This review focuses on the history and current state of photoreceptor and retinal pigment epithelium (RPE) cell generation from PSCs. We explore the applications of this technology in disease modelling, experimental therapy testing, biomarker identification, and toxicity studies. We consider challenges in scalability, standardisation, and reproducibility, and stress the importance of incorporating vasculature and immune cells into retinal organoids. We advocate for high-throughput automation in data acquisition and analyses and underscore the value of advanced micro-physiological systems that fully capture the interactions between the neural retina, RPE, and choriocapillaris.

One-step in vivo gene knock-out in porcine embryos using recombinant adeno-associated viruses

Introduction: Gene-edited pigs have become prominent models for studying human disease mechanisms, gene therapy, and xenotransplantation. CRISPR (clustered regularly interspaced short palindromic repeats)/CRISPR-associated 9 (CRISPR/Cas9) technology is a widely employed tool for generating gene-edited pigs. Nevertheless, delivering CRISPR/Cas9 to pre-implantation embryos has traditionally posed challenges due to its reliance on intricate micromanipulation equipment and specialized techniques, resulting in high costs and time-consuming procedures. This study aims to introduce a novel one-step approach for generating genetically modified pigs by transducing CRISPR/Cas9 components into pre-implantation porcine embryos through oviductal injection of recombinant adeno-associated viruses (rAAV). Methods: We first used rAAV-1, rAAV-6, rAAV-8, rAAV-9 expressing EGFP to screen for rAAV serotypes that efficiently target porcine embryos, and then, to achieve efficient expression of CRISPR/Cas9 in vivo for a short period, we packaged sgRNAs targeting the GHR genes to self-complementary adeno-associated virus (scAAV), and Cas9 proteins to single-stranded adeno-associated virus (ssAAV). The efficiency of porcine embryos -based editing was then validated in vitro. The feasibility of this one-step method to produce gene-edited pigs using rAAV-CRISPR/Cas9 oviductal injection into sows within 24 h of conception was then validated. Results: Our research firstly establishes the efficient delivery of CRISPR/Cas9 to pig zygotes, both in vivo and in vitro, using rAAV6. Successful gene editing in pigs was achieved through oviductal injection of rAAV-CRISPR/Cas9. Conclusion: This method circumvents the intricate procedures involved in in vitro embryo manipulation and embryo transfers, providing a straightforward and cost-effective approach for the production of gene-edited pigs.

Splicing defects and CRISPR-Cas9 correction in isogenic homozygous photoreceptor precursors harboring clustered deep-intronic ABCA4 variants

Splicing defects from deep-intronic variants significantly contribute to the mutational spectrum in ABCA4-associated inherited retinal diseases, necessitating functional validation for their pathological classification. Typically, minigene assays in HEK293(T) can qualitatively assess splicing defects, yet they often fail to quantitatively reproduce the resulting mis-splicing patterns, leaving uncertainty on severity and pathogenicity. As a potential cellular model derived from patient cells, photoreceptor precursor cells (PPCs) play a pivotal role in assessing the severity of specific splicing mutations. Nevertheless, the accessibility of biosamples is commonly constrained, and their establishment is costly and laborious. In this study, we combined and investigated the use of a minigene assay and isogenic PPCs, as superior qualitative and more accessible cellular models for the assessment of splicing defects. Specifically, we focused on the clustered c.5196+1013A>G, c.5196+1056A>G, and c.5196+1216C>A deep-intronic variants in intron 36 of ABCA4, comparing their resulting (mis)splicing patterns in minigene-transfected cells and isogenic CRISPR-Cas9-knocked-in PPCs harboring these pathogenic variants in homozygous state. Moreover, we demonstrate the successful correction of these three splicing defects in homozygous mutant PPCs using a single pair of guide RNAs to target Cas9 cleavage, thereby identifying an efficient gene editing strategy for therapeutic applications.

Cell-cell interaction in the pathogenesis of inherited retinal diseases

The retina is part of the central nervous system specialized for vision. Inherited retinal diseases (IRD) are a group of clinically and genetically heterogenous disorders that lead to progressive vision impairment or blindness. Although each disorder is rare, IRD accumulatively cause blindness in up to 5.5 million individuals worldwide. Currently, the pathophysiological mechanisms of IRD are not fully understood and there are limited treatment options available. Most IRD are caused by degeneration of light-sensitive photoreceptors. Genetic mutations that abrogate the structure and/or function of photoreceptors lead to visual impairment followed by blindness caused by loss of photoreceptors. In healthy retina, photoreceptors structurally and functionally interact with retinal pigment epithelium (RPE) and Müller glia (MG) to maintain retinal homeostasis. Multiple IRD with photoreceptor degeneration as a major phenotype are caused by mutations of RPE- and/or MG-associated genes. Recent studies also reveal compromised MG and RPE caused by mutations in ubiquitously expressed ciliary genes. Therefore, photoreceptor degeneration could be a direct consequence of gene mutations and/or could be secondary to the dysfunction of their interaction partners in the retina. This review summarizes the mechanisms of photoreceptor-RPE/MG interaction in supporting retinal functions and discusses how the disruption of these processes could lead to photoreceptor degeneration, with an aim to provide a unique perspective of IRD pathogenesis and treatment paradigm. We will first describe the biology of retina and IRD and then discuss the interaction between photoreceptors and MG/RPE as well as their implications in disease pathogenesis. Finally, we will summarize the recent advances in IRD therapeutics targeting MG and/or RPE.

CRISPR Advancements for Human Health

CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) has emerged as a powerful gene editing technology that is revolutionizing biomedical research and clinical medicine. The CRISPR system allows scientists to rewrite the genetic code in virtually any organism. This review provides a comprehensive overview of CRISPR and its clinical applications. We first introduce the CRISPR system and explain how it works as a gene editing tool. We then highlight current and potential clinical uses of CRISPR in areas such as genetic disorders, infectious diseases, cancer, and regenerative medicine. Challenges that need to be addressed for the successful translation of CRISPR to the clinic are also discussed. Overall, CRISPR holds great promise to advance precision medicine, but ongoing research is still required to optimize delivery, efficacy, and safety.

Therapeutic applications of CRISPR/Cas9 gene editing technology for the treatment of ocular diseases

Ocular diseases are a highly heterogeneous group of phenotypes, caused by a spectrum of genetic variants and environmental factors that exhibit diverse clinical symptoms. As a result of its anatomical location, structure and immune privilege, the eye is an ideal system to assess and validate novel genetic therapies. Advances in genome editing have revolutionized the field of biomedical science, enabling researchers to understand the biology behind disease mechanisms and allow the treatment of several health conditions, including ocular pathologies. The advent of clustered regularly interspaced short palindromic repeats (CRISPR)-based gene editing facilitates efficient and specific genetic modifications in the nucleic acid sequence, resulting in permanent changes at the genomic level. This approach has advantages over other treatment strategies and is promising for the treatment of various genetic and non-genetic ocular conditions. This review provides an overview of the CRISPR/CRISPR-associated protein 9 (Cas9) system and summarizes recent advances in the therapeutic application of CRISPR/Cas9 for the treatment of various ocular pathologies, as well as future challenges.

Tunable metal-organic frameworks assist in catalyzing DNAzymes with amplification platforms for biomedical applications

Various binding modes of tunable metal organic frameworks (MOFs) and functional DNAzymes (Dzs) synergistically catalyze the emergence of abundant functional nanoplatforms. Given their serial variability in formation, structural designability, and functional controllability, Dzs@MOFs tend to be excellent building blocks for the precise "intelligent" manufacture of functional materials. To present a clear outline of this new field, this review systematically summarizes the progress of Dz integration into MOFs (MOFs@Dzs) through different methods, including various surface infiltration, pore encapsulation, covalent binding, and biomimetic mineralization methods. Atomic-level and time-resolved catalytic mechanisms for biosensing and imaging are made possible by the complex interplay of the distinct molecular structure of Dzs@MOF, conformational flexibility, and dynamic regulation of metal ions. Exploiting the precision of DNAzymes, MOFs@Dzs constructed a combined nanotherapy platform to guide intracellular drug synthesis, photodynamic therapy, catalytic therapy, and immunotherapy to enhance gene therapy in different ways, solving the problems of intracellular delivery inefficiency and insufficient supply of cofactors. MOFs@Dzs nanostructures have become excellent candidates for biosensing, bioimaging, amplification delivery, and targeted cancer gene therapy while emphasizing major advancements and seminal endeavors in the fields of biosensing (nucleic acid, protein, enzyme activity, small molecules, and cancer cells), biological imaging, and targeted cancer gene delivery and gene therapy. Overall, based on the results demonstrated to date, we discuss the challenges that the emerging MOFs@Dzs might encounter in practical future applications and briefly look forward to their bright prospects in other fields.

What did CRISPR-Cas9 accomplish in its first 10 years?

It's been 10 years now from the debut of clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR/Cas9) era in which gene engineering has never been so accessible, precise and efficient. This technology, like a refined surgical procedure, has offered the ability of removing different types of disease causing mutations and restoring key proteins activity with ease of outperforming the previous resembling methods: zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs). Additionally, CRISPR-Cas9 systems can systematically introduce genetic sequences to the specific sites in the human genome allowing to stimulate desired functions such as anti-tumoral and anti-infectious faculties. The present brief review provides an updated resume of CRISPR-Cas9's top achievements from its first appearance to the current date focusing on the breakthrough research including in vitro, in vivo and human studies. This enables the evaluation of the previous phase 'the proof-of-concept phase' and marks the beginning of the next phase which will probably bring a spate of clinical trials.

New horizons in aniridia management: Clinical insights and therapeutic advances

Congenital aniridia is a rare genetic eye disorder characterized by the complete or partial absence of the iris from birth. Various theories and animal models have been proposed to understand and explain the pathogenesis of aniridia. In the majority of cases, aniridia is caused by a mutation in the PAX6 gene, which affects multiple structures within the eye. Treating these ocular complications is challenging and carries a high risk of side effects. However, emerging approaches for the treatment of aniridia-associated keratopathy, iris abnormalities, cataract abnormalities, and foveal hypoplasia show promise for improved outcomes. Genetic counseling plays a very important role to make informed choices. We also provide an overview of the newer diagnostic and therapeutic approaches such as next generation sequencing, gene therapy, in vivo silencing, and miRNA modulation.

A Report on Children with CEP290 Mutation, Vision Loss, and Developmental Delay

Mutations in CEP290, which encodes a centrosomal protein, cause Joubert syndrome, retinal dystrophy, and several other manifestations. Retinal dystrophy related to CEP290 mutation (Leber's congenital amaurosis type 10) presents with a severe visual impairment from birth, wandering eye movements, and oculodigital reflex. Fundus examination may initially be normal, but varying degrees of retinal pigmentation can be detected over time. This report presents 4 children who were referred to the ophthalmology clinic with a lack of eye contact and the suspicion of low vision. The ophthalmological examination revealed very poor visual function, the vision slightly improved over time, and enophthalmos became evident. There was neuromotor retardation in their history and mutations in the CEP290 gene were revealed in the whole-exome analysis. Both pediatricians and ophthalmologists should be aware of the coincidence between severe vision loss and neuromotor retardation and should refer patients for genetic testing if they suspect it. Genetic diagnosis will enable patients to be followed both neurologically and ophthalmologically and to benefit from rehabilitation opportunities that will contribute to visual and neurological development. It will also allow the family to receive genetic counseling on disease progression and heredity, and to follow ongoing gene therapy studies for mutations in the relevant gene.

CRISPR-Cas Technology as a Revolutionary Genome Editing tool: Mechanisms and Biomedical Applications

Programmable nucleases are powerful genomic tools for precise genome editing. These tools precisely recognize, remove, or change DNA at a defined site, thereby, stimulating cellular DNA repair pathways that can cause mutations or accurate replacement or deletion/insertion of a sequence. CRISPR-Cas9 system is the most potent and useful genome editing technique adapted from the defense immune system of certain bacteria and archaea against viruses and phages. In the past decade, this technology made notable progress, and at present, it has largely been used in genome manipulation to make precise gene editing in plants, animals, and human cells. In this review, we aim to explain the basic principle, mechanisms of action, and applications of this system in different areas of medicine, with emphasizing on the detection and treatment of parasitic diseases.

Clinical and Molecular Aspects of C2orf71/PCARE in Retinal Diseases

Mutations in the photoreceptor-specific C2orf71 gene (also known as photoreceptor cilium actin regulator protein PCARE) cause autosomal recessive retinitis pigmentosa type 54 and cone-rod dystrophy. No treatments are available for patients with C2orf71 retinal ciliopathies exhibiting a severe clinical phenotype. Our understanding of the disease process and the role of PCARE in the healthy retina significantly limits our capacity to transfer recent technical developments into viable therapy choices. This study summarizes the current understanding of C2orf71-related retinal diseases, including their clinical manifestations and an unclear genotype-phenotype correlation. It discusses molecular and functional studies on the photoreceptor-specific ciliary PCARE, focusing on the photoreceptor cell and its ciliary axoneme. It is proposed that PCARE is an actin-associated protein that interacts with WASF3 to regulate the actin-driven expansion of the ciliary membrane during the development of a new outer segment disk in photoreceptor cells. This review also introduces various cellular and animal models used to model these diseases and provides an overview of potential treatments.

Adeno-associated virus mediated gene therapy for neuroprotection of retinal ganglion cells in glaucoma

Glaucoma is a group of diseases typically characterized by the degeneration of the optic nerve and is one of the world's leading causes of blindness. Although there is no cure for glaucoma, reducing intraocular pressure is an approved treatment to delay optic nerve degeneration and retinal ganglion cell (RGC) death in most patients. Recent clinical trials have evaluated the safety and efficacy of gene therapy vectors for the treatment of inherited retinal degenerations (IRDs), and the results are promising, generating enthusiasm for the treatment of other retinal diseases. While there have been no reports on successful clinical trials for gene therapy-based neuroprotective treatment of glaucoma, and only a few studies assessing the efficacy of gene therapy vectors for the treatment of Leber hereditary optic neuropathy (LHON), the potential for neuroprotective treatment of glaucoma and other diseases affecting RGCs is still widely recognized. Here, we review recent progress and cover current limitations pertaining to targeting RGCs with adeno-associated virus-based gene therapy for the treatment of glaucoma.

Recent advances in therapeutic CRISPR-Cas9 genome editing: mechanisms and applications

Recently, clustered regularly interspaced palindromic repeats (CRISPR)-Cas9 derived editing tools had significantly improved our ability to make desired changes in the genome. Wild-type Cas9 protein recognizes the target genomic loci and induced local double strand breaks (DSBs) in the guidance of small RNA molecule. In mammalian cells, the DSBs are mainly repaired by endogenous non-homologous end joining (NHEJ) pathway, which is error prone and results in the formation of indels. The indels can be harnessed to interrupt gene coding sequences or regulation elements. The DSBs can also be fixed by homology directed repair (HDR) pathway to introduce desired changes, such as base substitution and fragment insertion, when proper donor templates are provided, albeit in a less efficient manner. Besides making DSBs, Cas9 protein can be mutated to serve as a DNA binding platform to recruit functional modulators to the target loci, performing local transcriptional regulation, epigenetic remolding, base editing or prime editing. These Cas9 derived editing tools, especially base editors and prime editors, can introduce precise changes into the target loci at a single-base resolution and in an efficient and irreversible manner. Such features make these editing tools very promising for therapeutic applications. This review focuses on the evolution and mechanisms of CRISPR-Cas9 derived editing tools and their applications in the field of gene therapy.

Transcriptional reprogramming restores UBE3A brain-wide and rescues behavioral phenotypes in an Angelman syndrome mouse model

Angelman syndrome (AS) is a neurogenetic disorder caused by the loss of ubiquitin ligase E3A (UBE3A) gene expression in the brain. The UBE3A gene is paternally imprinted in brain neurons. Clinical features of AS are primarily due to the loss of maternally expressed UBE3A in the brain. A healthy copy of paternal UBE3A is present in the brain but is silenced by a long non-coding antisense transcript (UBE3A-ATS). Here, we demonstrate that an artificial transcription factor (ATF-S1K) can silence Ube3a-ATS in an adult mouse model of Angelman syndrome (AS) and restore endogenous physiological expression of paternal Ube3a. A single injection of adeno-associated virus (AAV) expressing ATF-S1K (AAV-S1K) into the tail vein enabled whole-brain transduction and restored UBE3A protein in neurons to ∼25% of wild-type protein. The ATF-S1K treatment was highly specific to the target site with no detectable inflammatory response 5 weeks after AAV-S1K administration. AAV-S1K treatment of AS mice showed behavioral rescue in exploratory locomotion, a task involving gross and fine motor abilities, similar to low ambulation and velocity in AS patients. The specificity and tolerability of a single injection of AAV-S1K therapy for AS demonstrate the use of ATFs as a promising translational approach for AS.

Silk-Gel Powered Adenoviral Vector Enables Robust Genome Editing of PD-L1 to Augment Immunotherapy across Multiple Tumor Models

Immune checkpoint blockade based on antibodies has shown great clinical success in patients, but the transitory working manner leads to restricted therapeutic benefits. Herein, a genetically engineered adenovirus is developed as the vector to deliver CRISPR/Cas9 (sgCas9-AdV) to achieve permanent PD-L1 gene editing with efficiency up to 78.7% exemplified in Hepa 1-6 liver cancer cells. Furthermore, the sgCas9-AdV is loaded into hydrogel made by silk fiber (SgCas9-AdV/Gel) for in vivo application. The silk-gel not only promotes local retention of sgCas9-AdV in tumor tissue, but also masks them from host immune system, thus ensuring effectively gene transduction over 9 days. Bearing these advantages, the sgCas9-AdV/Gel inhibits Hepa 1-6 tumor growth with 100% response rate by single-dose injection, through efficient PD-L1 disruption to elicit a T cell-mediated antitumor response. In addition, the sgCas9-AdV/Gel is also successfully extended into other refractory tumors. In CT26 colon tumor characterized by poor response to anti-PD-L1, sgCas9-AdV/Gel is demonstrated to competent and superior anti-PD-L1 antibody to suppress tumor progression. In highly aggressive orthotopic 4T1 mouse breast tumor, such a therapeutic paradigm significantly inhibits primary tumor growth and induces a durable immune response against tumor relapse/metastasis. Thus, this study provides an attractive and universal strategy for immunotherapy.

The application and progression of CRISPR/Cas9 technology in ophthalmological diseases

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated nuclease (Cas) system is an adaptive immune defence system that has gradually evolved in bacteria and archaea to combat invading viruses and exogenous DNA. Advances in technology have enabled researchers to enhance their understanding of the immune process in vivo and its potential for use in genome editing. Thus far, applications of CRISPR/Cas9 genome editing technology in ophthalmology have included gene therapy for corneal dystrophy, glaucoma, congenital cataract, Leber's congenital amaurosis, retinitis pigmentosa, Usher syndrome, fundus neovascular disease, proliferative vitreoretinopathy, retinoblastoma and other eye diseases. Additionally, the combination of CRISPR/Cas9 genome editing technology with adeno-associated virus vector and inducible pluripotent stem cells provides further therapeutic avenues for the treatment of eye diseases. Nonetheless, many challenges remain in the development of clinically feasible retinal genome editing therapy. This review discusses the development, as well as mechanism of CRISPR/Cas9 and its applications and challenges in gene therapy for eye diseases.

Immunogenicity of CRISPR therapeutics-Critical considerations for clinical translation

CRISPR offers new hope for many patients and promises to transform the way we think of future therapies. Ensuring safety of CRISPR therapeutics is a top priority for clinical translation and specific recommendations have been recently released by the FDA. Rapid progress in the preclinical and clinical development of CRISPR therapeutics leverages years of experience with gene therapy successes and failures. Adverse events due to immunogenicity have been a major setback that has impacted the field of gene therapy. As several in vivo CRISPR clinical trials make progress, the challenge of immunogenicity remains a significant roadblock to the clinical availability and utility of CRISPR therapeutics. In this review, we examine what is currently known about the immunogenicity of CRISPR therapeutics and discuss several considerations to mitigate immunogenicity for the design of safe and clinically translatable CRISPR therapeutics.

TAxI-peptide targeted Cas12a ribonuclease protein nanoformulations increase genome editing in hippocampal neurons

Gene therapy approaches that utilize Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) ribonucleases have tremendous potential to treat human disease. However, CRISPR therapies delivered by integrating viral vectors are limited by potential off-target genome editing caused by constitutive activation of ribonuclease functions. Thus, biomaterial formulations are being used for the delivery of purified CRISPR components to increase the efficiency and safety of genome editing approaches. We previously demonstrated that a novel peptide identified by phage display, TAxI-peptide, mediates delivery of recombinant proteins into neurons. In this report we utilized NeutrAvidin protein to formulate neuron-targeted genome-editing nanoparticles. Cas12a ribonucleases was loaded with biotinylated guide RNA and biotinylated TAxI-peptide onto NeutrAvidin protein to coordinate the formation a targeted ribonuclease protein (RNP) complex. TAxI-RNP complexes are polydisperse with a 14.3 nm radius. The nanoparticles are stable after formulation and show good stability in the presence of normal mouse serum. TAxI-RNP nanoparticles increased neuronal delivery of Cas12a in reporter mice, resulting in induced tdTomato expression after direct injection into the dentate gyrus of the hippocampus. TAxI-RNP nanoparticles also increased genome editing efficacy in hippocampal neurons versus glia. These studies demonstrate the ability to assemble RNP nanoformulations with NeutrAvidin by binding biotinylated peptides and gRNA-loaded Cas12a ribonucleases into protein nanoparticles that target CRISPR delivery to specific cell-types in vivo. The potential to deliver CRISPR nanoparticles to specific cell-types and control off-target delivery to further reduce deleterious genome editing is essential for the creation of viable therapies to treat nervous system disease.

CRISPR-Based Tools for Fighting Rare Diseases

Rare diseases affect the life of a tremendous number of people globally. The CRISPR-Cas system emerged as a powerful genome engineering tool and has facilitated the comprehension of the mechanism and development of therapies for rare diseases. This review focuses on current efforts to develop the CRISPR-based toolbox for various rare disease therapy applications and compares the pros and cons of different tools and delivery methods. We further discuss the therapeutic applications of CRISPR-based tools for fighting different rare diseases.

CRISPR/Cas systems: Delivery and application in gene therapy

The CRISPR/Cas systems in prokaryotes such as bacteria and archaea are the adaptive immune system to prevent infection from viruses, phages, or other foreign substances. When viruses or phages first invade the bacteria, Cas proteins recognize and cut the DNA from viruses or phages into short fragments that will be integrated into the CRISPR array. Once bacteria are invaded again, the modified CRISPR and Cas proteins react quickly to cut DNA at the specified target location, protecting the host. Due to its high efficiency, versatility, and simplicity, the CRISPR/Cas system has become one of the most popular gene editing technologies. In this review, we briefly introduce the CRISPR/Cas systems, focus on several delivery methods including physical delivery, viral vector delivery, and non-viral vector delivery, and the applications of disease therapy. Finally, some problems in CRISPR/Cas9 technology have been proposed, such as the off-target effects, the efficiency of DNA repair mechanisms, and delivery of CRISPR/Cas system safely and efficiently to the target location.

Clinical trials and promising preclinical applications of CRISPR/Cas gene editing

Treatment of genetic disorders by genomic manipulation has been the unreachable goal of researchers for many decades. Although our understanding of the genetic basis of genetic diseases has advanced tremendously in the last few decades, the tools developed for genomic editing were not efficient and practical for their use in the clinical setting until now. The recent advancements in the research of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated protein (Cas) systems offered an easy and efficient way to edit the genome and accelerated the research on their potential use in the treatment of genetic disorders. In this review, we summarize the clinical trials that evaluate the CRISPR/Cas systems for treating different genetic diseases and highlight promising preclinical research on CRISPR/Cas mediated treatment of a great diversity of genetic disorders. Ultimately, we discuss the future of CRISPR/Cas mediated genome editing in genetic diseases.

The retinal pigmentation pathway in human albinism: Not so black and white

Albinism is a pigment disorder affecting eye, skin and/or hair. Patients usually have decreased melanin in affected tissues and suffer from severe visual abnormalities, including foveal hypoplasia and chiasmal misrouting. Combining our data with those of the literature, we propose a single functional genetic retinal signalling pathway that includes all 22 currently known human albinism disease genes. We hypothesise that defects affecting the genesis or function of different intra-cellular organelles, including melanosomes, cause syndromic forms of albinism (Hermansky-Pudlak (HPS) and Chediak-Higashi syndrome (CHS)). We put forward that specific melanosome impairments cause different forms of oculocutaneous albinism (OCA1-8). Further, we incorporate GPR143 that has been implicated in ocular albinism (OA1), characterised by a phenotype limited to the eye. Finally, we include the SLC38A8-associated disorder FHONDA that causes an even more restricted "albinism-related" ocular phenotype with foveal hypoplasia and chiasmal misrouting but without pigmentation defects. We propose the following retinal pigmentation pathway, with increasingly specific genetic and cellular defects causing an increasingly specific ocular phenotype: (HPS1-11/CHS: syndromic forms of albinism)-(OCA1-8: OCA)-(GPR143: OA1)-(SLC38A8: FHONDA). Beyond disease genes involvement, we also evaluate a range of (candidate) regulatory and signalling mechanisms affecting the activity of the pathway in retinal development, retinal pigmentation and albinism. We further suggest that the proposed pigmentation pathway is also involved in other retinal disorders, such as age-related macular degeneration. The hypotheses put forward in this report provide a framework for further systematic studies in albinism and melanin pigmentation disorders.

Quantification of Genome Editing and Transcriptional Control Capabilities Reveals Hierarchies among Diverse CRISPR/Cas Systems in Human Cells

CRISPR/Cas technologies have revolutionized the ability to redesign genomic information and tailor endogenous gene expression. Nevertheless, the discovery and development of new CRISPR/Cas systems has resulted in a lack of clarity surrounding the relative efficacies among these technologies in human cells. This deficit makes the optimal selection of CRISPR/Cas technologies in human cells unnecessarily challenging, which in turn hampers their adoption, and thus ultimately limits their utility. Here, we designed a series of endogenous testbed systems to methodically quantify and compare the genome editing, CRISPRi, and CRISPRa capabilities among 10 different natural and engineered Cas protein variants spanning Type II and Type V CRISPR/Cas families. We show that although all Cas protein variants are capable of genome editing and transcriptional control in human cells, hierarchies exist, particularly for genome editing and CRISPRa applications, wherein Cas9 ≥ Cas12a > Cas12e/Cas12j. Our findings also highlight the utility of our modular testbed platforms to rapidly and systematically quantify the functionality of practically any natural or engineered genomic-targeting Cas protein in human cells.

Gene regulatory and gene editing tools and their applications for retinal diseases and neuroprotection: From proof-of-concept to clinical trial

Gene editing and gene regulatory fields are continuously developing new and safer tools that move beyond the initial CRISPR/Cas9 technology. As more advanced applications are emerging, it becomes crucial to understand and establish more complex gene regulatory and editing tools for efficient gene therapy applications. Ophthalmology is one of the leading fields in gene therapy applications with more than 90 clinical trials and numerous proof-of-concept studies. The majority of clinical trials are gene replacement therapies that are ideal for monogenic diseases. Despite Luxturna's clinical success, there are still several limitations to gene replacement therapies including the size of the target gene, the choice of the promoter as well as the pathogenic alleles. Therefore, further attempts to employ novel gene regulatory and gene editing applications are crucial to targeting retinal diseases that have not been possible with the existing approaches. CRISPR-Cas9 technology opened up the door for corrective gene therapies with its gene editing properties. Advancements in CRISPR-Cas9-associated tools including base modifiers and prime editing already improved the efficiency and safety profile of base editing approaches. While base editing is a highly promising effort, gene regulatory approaches that do not interfere with genomic changes are also becoming available as safer alternatives. Antisense oligonucleotides are one of the most commonly used approaches for correcting splicing defects or eliminating mutant mRNA. More complex gene regulatory methodologies like artificial transcription factors are also another developing field that allows targeting haploinsufficiency conditions, functionally equivalent genes, and multiplex gene regulation. In this review, we summarized the novel gene editing and gene regulatory technologies and highlighted recent translational progress, potential applications, and limitations with a focus on retinal diseases.

CRISPR/Cas systems usher in a new era of disease treatment and diagnosis

The discovery and development of the CRISPR/Cas system is a milestone in precise medicine. CRISPR/Cas nucleases, base-editing (BE) and prime-editing (PE) are three genome editing technologies derived from CRISPR/Cas. In recent years, CRISPR-based genome editing technologies have created immense therapeutic potential with safe and efficient viral or non-viral delivery systems. Significant progress has been made in applying genome editing strategies to modify T cells and hematopoietic stem cells (HSCs) ex vivo and to treat a wide variety of diseases and disorders in vivo. Nevertheless, the clinical translation of this unique technology still faces many challenges, especially targeting, safety and delivery issues, which require further improvement and optimization. In addition, with the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), CRISPR-based molecular diagnosis has attracted extensive attention. Growing from the specific set of molecular biological discoveries to several active clinical trials, CRISPR/Cas systems offer the opportunity to create a cost-effective, portable and point-of-care diagnosis through nucleic acid screening of diseases. In this review, we describe the development, mechanisms and delivery systems of CRISPR-based genome editing and focus on clinical and preclinical studies of therapeutic CRISPR genome editing in disease treatment as well as its application prospects in therapeutics and molecular detection.

In vivo application of base and prime editing to treat inherited retinal diseases

Inherited retinal diseases (IRDs) are vision-threatening retinal disorders caused by pathogenic variants of genes related to visual functions. Genomic analyses in patients with IRDs have revealed pathogenic variants which affect vision. However, treatment options for IRDs are limited to nutritional supplements regardless of genetic variants or gene-targeting approaches based on antisense oligonucleotides and adeno-associated virus vectors limited to targeting few genes. Genome editing, particularly that involving clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 technologies, can correct pathogenic variants and provide additional treatment opportunities. Recently developed base and prime editing platforms based on CRISPR-Cas9 technologies are promising for therapeutic genome editing because they do not employ double-stranded breaks (DSBs), which are associated with P53 activation, large deletions, and chromosomal translocations. Instead, using attached deaminases and reverse transcriptases, base and prime editing efficiently induces specific base substitutions and intended genetic changes (substitutions, deletions, or insertions), respectively, without DSBs. In this review, we will discuss the recent in vivo application of CRISPR-Cas9 technologies, focusing on base and prime editing, in animal models of IRDs.

Emerging Gene Manipulation Strategies for the Treatment of Monogenic Eye Disease

Genetic eye diseases, representing a wide spectrum of simple and complex conditions, are one of the leading causes of visual loss in children and working adults, and progress in the field has led to changes in disease investigation, diagnosis, and management. The past 15 years have seen the emergence of novel therapies for these previously untreatable conditions to the extent that we now have a licensed therapy for one form of genetic eye disease and many more in clinical trial. This is a systematic review of published and ongoing clinical trials of gene therapies for monogenic eye diseases. Databases of clinical trials and the published literature were searched for interventional studies of gene therapies for eye diseases. Standard methodological procedures were used to assess the relevance of search results. A total of 59 registered clinical trials are referenced, showing the significant level of interest in the potential for translation of these therapies from bench to bedside. The breadth of therapy design is encouraging, providing multiple possible therapeutic mechanisms. Some fundamental questions regarding gene therapy for genetic eye diseases remain, such as optimal dosing, the relative benefits of adeno-associated virus (AAV)-packaging and the potential for a significant inflammatory response to the therapy itself. As a result, despite the promise of the eye as a target, it has proven difficult to deliver clinically effective gene therapies to the eye. Despite setbacks, the licensing of Luxturna (voretigene neparvovec, Novartis) for the treatment of RPE65-mediated Leber congenital amaurosis (LCA) is a major advance in efforts to treat these rare, but devastating, causes of visual loss.

Targeting the HDAC6-Cilium Axis Ameliorates the Pathological Changes Associated with Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is one of the leading causes of childhood visual impairment and blindness. However, there are still very few effective pharmacological interventions for ROP. Histone deacetylase 6 (HDAC6)-mediated disassembly of photoreceptor cilia has recently been implicated as an early event in the pathogenesis of ROP. Herein it is shown that enhanced expression of HDAC6 by intravitreal injection of adenoviruses encoding HDAC6 induces the typical pathological changes associated with ROP in mice, including disruption of the membranous disks of photoreceptor outer segments and a decrease in electroretinographic amplitudes. Hdac6 transgenic mice exhibit similar ROP-related defects in retinal structures and functions and disassembly of photoreceptor cilia, whereas Hdac6 knockout mice are resistant to oxygen change-induced retinal defects. It is further shown that blocking HDAC6-mediated cilium disassembly by intravitreal injection of small-molecule compounds protect mice from ROP-associated retinal defects. The findings indicate that pharmacological targeting of the HDAC6-cilium axis may represent a promising strategy for the prevention of ROP.

Development of clustered regularly interspaced short palindromic repeats/CRISPR-associated technology for potential clinical applications

The clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated (Cas) proteins constitute the innate adaptive immune system in several bacteria and archaea. This immune system helps them in resisting the invasion of phages and foreign DNA by providing sequence-specific acquired immunity. Owing to the numerous advantages such as ease of use, low cost, high efficiency, good accuracy, and a diverse range of applications, the CRISPR-Cas system has become the most widely used genome editing technology. Hence, the advent of the CRISPR/Cas technology highlights a tremendous potential in clinical diagnosis and could become a powerful asset for modern medicine. This study reviews the recently reported application platforms for screening, diagnosis, and treatment of different diseases based on CRISPR/Cas systems. The limitations, current challenges, and future prospectus are summarized; this article would be a valuable reference for future genome-editing practices.

Simulation-Based Engineering of Time-Delayed Safety Switches for Safer Gene Therapies

CRISPR-based gene editing is a powerful tool with great potential for applications in the treatment of many inherited and acquired diseases. The longer that CRISPR gene therapy is maintained within a patient, however, the higher the likelihood that it will result in problematic side effects such as off-target editing or immune response. One approach to mitigating these issues is to link the operation of the therapeutic system to a safety switch that autonomously disables its operation and removes the delivered therapeutics after some amount of time. We present here a simulation-based analysis of the potential for regulating the time delay of such a safety switch using one or two transcriptional regulators and/or recombinases. Combinatorial circuit generation identifies 30 potential architectures for such circuits, which we evaluate in simulation with respect to tunability, sensitivity to parameter values, and sensitivity to cell-to-cell variation. This modeling predicts one of these circuit architectures to have the desired dynamics and robustness, which can be further tested and applied in the context of CRISPR therapeutics.

Nanodelivery of nucleic acids

There is growing need for a safe, efficient, specific and non-pathogenic means for delivery of gene therapy materials. Nanomaterials for nucleic acid delivery offer an unprecedented opportunity to overcome these drawbacks; owing to their tunability with diverse physico-chemical properties, they can readily be functionalized with any type of biomolecules/moieties for selective targeting. Nucleic acid therapeutics such as antisense DNA, mRNA, small interfering RNA (siRNA) or microRNA (miRNA) have been widely explored to modulate DNA or RNA expression Strikingly, gene therapies combined with nanoscale delivery systems have broadened the therapeutic and biomedical applications of these molecules, such as bioanalysis, gene silencing, protein replacement and vaccines. Here, we overview how to design smart nucleic acid delivery methods, which provide functionality and efficacy in the layout of molecular diagnostics and therapeutic systems. It is crucial to outline some of the general design considerations of nucleic acid delivery nanoparticles, their extraordinary properties and the structure-function relationships of these nanomaterials with biological systems and diseased cells and tissues.

Strategies for High-Efficiency Mutation Using the CRISPR/Cas System

Clustered regularly interspaced short palindromic repeats (CRISPR)-associated systems have revolutionized traditional gene-editing tools and are a significant tool for ameliorating gene defects. Characterized by high target specificity, extraordinary efficiency, and cost-effectiveness, CRISPR/Cas systems have displayed tremendous potential for genetic manipulation in almost any organism and cell type. Despite their numerous advantages, however, CRISPR/Cas systems have some inherent limitations, such as off-target effects, unsatisfactory efficiency of delivery, and unwanted adverse effects, thereby resulting in a desire to explore approaches to address these issues. Strategies for improving the efficiency of CRISPR/Cas-induced mutations, such as reducing off-target effects, improving the design and modification of sgRNA, optimizing the editing time and the temperature, choice of delivery system, and enrichment of sgRNA, are comprehensively described in this review. Additionally, several newly emerging approaches, including the use of Cas variants, anti-CRISPR proteins, and mutant enrichment, are discussed in detail. Furthermore, the authors provide a deep analysis of the current challenges in the utilization of CRISPR/Cas systems and the future applications of CRISPR/Cas systems in various scenarios. This review not only serves as a reference for improving the maturity of CRISPR/Cas systems but also supplies practical guidance for expanding the applicability of this technology.

Review of gene therapies for age-related macular degeneration

Gene therapies aim to deliver a therapeutic payload to specified tissues with underlying protein deficiency. Since the 1990s, gene therapies have been explored as potential treatments for chronic conditions requiring lifetime care and medical management. Ocular gene therapies target a range of ocular disorders, but retinal diseases are of particular importance due to the prevalence of retinal disease and the current treatment burden of such diseases on affected patients, as well as the challenge of properly delivering these therapies to the target tissue. The purpose of this review is to provide an update on the most current data available for five different retinal gene therapies currently undergoing clinical trials for use against age-related macular degeneration (AMD) and the development of novel delivery routes for the administration of such therapies. Research has been performed and compiled from PubMed and the select authors of this manuscript on the treatment and effectiveness of five current retinal gene therapies: Luxturna, ADVM-022, RGX-314, GT-005, and HMR59. We present the available data of current clinical trials for the treatment of neovascular and dry age-related macular degeneration with different AAV-based gene therapies. We also present current research on the progress of developing novel routes of administration for ocular gene therapies. Retinal gene therapies offer the potential for life-changing treatment for chronic conditions like age-related macular degeneration with a single administration. In doing so, gene therapies change the landscape of treatment options for these chronic conditions for both patient and provider.

Delivery of CRISPR-Cas tools for in vivo genome editing therapy: Trends and challenges

The discovery of clustered regularly interspaced short palindromic repeats (CRISPR) genome editing technology opened the door to provide a versatile approach for treating multiple diseases. Promising results have been shown in numerous pre-clinical studies and clinical trials. However, a safe and effective method to deliver genome-editing components is still a key challenge for in vivo genome editing therapy. Adeno-associated virus (AAV) is one of the most commonly used vector systems to date, but immunogenicity against capsid, liver toxicity at high dose, and potential genotoxicity caused by off-target mutagenesis and genomic integration remain unsolved. Recently developed transient delivery systems, such as virus-like particle (VLP) and lipid nanoparticle (LNP), may solve some of the issues. This review summarizes existing in vivo delivery systems and possible solutions to overcome their limitations. Also, we highlight the ongoing clinical trials for in vivo genome editing therapy and recently developed genome editing tools for their potential applications.

Gene editing and its applications in biomedicine

The steady progress in genome editing, especially genome editing based on the use of clustered regularly interspaced short palindromic repeats (CRISPR) and programmable nucleases to make precise modifications to genetic material, has provided enormous opportunities to advance biomedical research and promote human health. The application of these technologies in basic biomedical research has yielded significant advances in identifying and studying key molecular targets relevant to human diseases and their treatment. The clinical translation of genome editing techniques offers unprecedented biomedical engineering capabilities in the diagnosis, prevention, and treatment of disease or disability. Here, we provide a general summary of emerging biomedical applications of genome editing, including open challenges. We also summarize the tools of genome editing and the insights derived from their applications, hoping to accelerate new discoveries and therapies in biomedicine.

Risk Mitigation of Immunogenicity: A Key to Personalized Retinal Gene Therapy

Gene therapy (GT) for ocular disorders has advanced the most among adeno-associated virus (AAV)-mediated therapies, with one product already approved in the market. The bank of retinal gene mutations carefully compiled over 30 years, the small retinal surface that does not require high clinical vector stocks, and the relatively immune-privileged environment of the eye explain such success. However, adverse effects due to AAV-delivery, though rare in the retina have led to the interruption of clinical trials. Risk mitigation, as the key to safe and efficient GT, has become the focus of 'bedside-back-to-bench' studies. Herein, we overview the inflammatory adverse events described in retinal GT trials and analyze which components of the retinal immunological environment might be the most involved in these immune responses, with a focus on the innate immune system composed of microglial surveillance. We consider the factors that can influence inflammation in the retina after GT such as viral sensors in the retinal tissue and CpG content in promoters or transgene sequences. Finally, we consider options to reduce the immunological risk, including dose, modified capsids or exclusion criteria for clinical trials. A better understanding and mitigation of immune risk factors inducing host immunity in AAV-mediated retinal GT is the key to achieving safe and efficient GT.