gene replacement
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2022 ◽  
Vol 12 ◽  
Author(s):  
Beau J. Fenner ◽  
Tien-En Tan ◽  
Amutha Veluchamy Barathi ◽  
Sai Bo Bo Tun ◽  
Sia Wey Yeo ◽  
...  

Inherited retinal diseases (IRDs) are a heterogenous group of orphan eye diseases that typically result from monogenic mutations and are considered attractive targets for gene-based therapeutics. Following the approval of an IRD gene replacement therapy for Leber’s congenital amaurosis due to RPE65 mutations, there has been an intensive international research effort to identify the optimal gene therapy approaches for a range of IRDs and many are now undergoing clinical trials. In this review we explore therapeutic challenges posed by IRDs and review current and future approaches that may be applicable to different subsets of IRD mutations. Emphasis is placed on five distinct approaches to gene-based therapy that have potential to treat the full spectrum of IRDs: 1) gene replacement using adeno-associated virus (AAV) and nonviral delivery vectors, 2) genome editing via the CRISPR/Cas9 system, 3) RNA editing by endogenous and exogenous ADAR, 4) mRNA targeting with antisense oligonucleotides for gene knockdown and splicing modification, and 5) optogenetic approaches that aim to replace the function of native retinal photoreceptors by engineering other retinal cell types to become capable of phototransduction.


2022 ◽  
Vol 12 ◽  
Author(s):  
Arianna Manini ◽  
Elena Abati ◽  
Andi Nuredini ◽  
Stefania Corti ◽  
Giacomo Pietro Comi

Duchenne muscular dystrophy (DMD) is an X-linked recessive, infancy-onset neuromuscular disorder characterized by progressive muscle weakness and atrophy, leading to delay of motor milestones, loss of autonomous ambulation, respiratory failure, cardiomyopathy, and premature death. DMD originates from mutations in the DMD gene that result in a complete absence of dystrophin. Dystrophin is a cytoskeletal protein which belongs to the dystrophin-associated protein complex, involved in cellular signaling and myofiber membrane stabilization. To date, the few available therapeutic options are aimed at lessening disease progression, but persistent loss of muscle tissue and function and premature death are unavoidable. In this scenario, one of the most promising therapeutic strategies for DMD is represented by adeno-associated virus (AAV)-mediated gene therapy. DMD gene therapy relies on the administration of exogenous micro-dystrophin, a miniature version of the dystrophin gene lacking unnecessary domains and encoding a truncated, but functional, dystrophin protein. Limited transgene persistence represents one of the most significant issues that jeopardize the translatability of DMD gene replacement strategies from the bench to the bedside. Here, we critically review preclinical and clinical studies of AAV-mediated gene therapy in DMD, focusing on long-term transgene persistence in transduced tissues, which can deeply affect effectiveness and sustainability of gene replacement in DMD. We also discuss the role played by the overactivation of the immune host system in limiting long-term expression of genetic material. In this perspective, further studies aimed at better elucidating the need for immune suppression in AAV-treated subjects are warranted in order to allow for life-long therapy in DMD patients.


2021 ◽  
Vol 20 (6s) ◽  
pp. 589-594
Author(s):  
Kristina S. Nevmerzhitskaya ◽  
Elena Yu. Sapego ◽  
Daria A. Morozova

Background. The efficacy and safety of onasemnogene abeparvovec have been demonstrated in patients with spinal muscular atrophy (SMA) in several clinical and observational studies. Gene replacement therapy results in Russian patients with SMA is not investigated yet.Objective. The aim of the study is to study the safety and efficacy of onasemnogene abeparvovec in children with SMA in real clinical practice.Methods. The study included patients with proximal 5q SMA administered with onasemnogene abeparvovec. Diagnosis was verified by biallelic deletion in the 7th exon of the SMN1 gene. Gene replacement therapy was administered according to the decision of neurologists consensus in case of the absence of antibodies to the adeno-associated serotype 9 virus. The therapy safety was estimated via clinical and laboratory data from the hospital (at least 7 days) and from outpatient departments (at least 60 days). Efficacy was estimated via CHOP INTEND scale and mastering new motor skills ≥ 6 months after therapy onset.Results. Treatment outcomes were studied in 10 SMA patients aged 19 months (15; 21). All patients developed at least one clinical manifestation (hyperthermia, vomiting, lethargy and/or loose stool) associated with drug administration during the first week of follow-up. Increased hepatic transaminases activity and monocytosis was recorded in all patients, thrombocytopenia — in 9, neutropenia — in 5, increased troponin I concentration — in 3. In three cases it was necessary to increase the oral prednisolone dose of to 2 mg/kg, in one case — the dexamethasone pulse therapy dose. The therapy efficacy was monitored ≥ 6 months after therapy onset via the CHOP INTEND scale in 2 patients (scores increased by 32 and 19 points, respectively), and via mastering new motor skills in 8 patients (positive dynamics was noted in 7 cases).Conclusion. The onasemnogene abeparvovec is relatively safe and quite effective for using in real clinical practice


Author(s):  
Jennifer M.I. Daenzer ◽  
Shauna A. Rasmussen ◽  
Sneh Patel ◽  
James McKenna ◽  
Judith L. Fridovich‐Keil

2021 ◽  
Vol 15 (1) ◽  
pp. 23
Author(s):  
Anna A. Shmidt ◽  
Tatiana V. Egorova

Recombinant adeno-associated viral vectors (rAAV) represent a gene therapy tool of ever-increasing importance. Their utilization as a delivery vehicle for gene replacement, silencing and editing, among other purposes, demonstrate considerable versatility. Emerging vector utilization in various experimental, preclinical and clinical applications establishes the necessity of producing and characterizing a wide variety of rAAV preparations. Critically important characteristics concerning quality control are rAAV titer quantification and the detection of impurities. Differences in rAAV constructs necessitate the development of highly standardized quantification assays to make direct comparisons of different preparations in terms of assembly or purification efficiency, as well as experimental or therapeutic dosages. The development of universal methods for impurities quantification is rather complicated, since variable production platforms are utilized for rAAV assembly. However, general agreements also should be achieved to address this issue. The majority of methods for rAAV quantification and quality control are based on PCR techniques. Despite the progress made, increasing evidence concerning high variability in titration assays indicates poor standardization of the methods undertaken to date. This review summarizes successes in the field of rAAV quality control and emphasizes ongoing challenges in PCR applications for rAAV characterization. General considerations regarding possible solutions are also provided.


2021 ◽  
Vol 3 ◽  
Author(s):  
Lei Zhu

Targeted gene knockout is particularly useful for analyzing gene functions in plant growth, signaling, and development. By transforming knockout cassettes consisting of homologous sequences of the target gene into protoplasts, the classical gene targeting method aims to obtain targeted gene replacement, allowing for the characterization of gene functions in vivo. The moss Physcomitrella patens is a known model organism for a high frequency of homologous recombination and thus harbors a remarkable rate of gene targeting. Other moss features, including easy to culture, dominant haploidy phase, and sequenced genome, make gene targeting prevalent in Physcomitrella patens. However, even gene targeting was powerful to generate knockouts, researchers using this method still experienced technical challenges. For example, obtaining a good number of targeted knockouts after protoplast transformation and regeneration disturbed the users. Off-target mutations such as illegitimate random integration mediated by nonhomologous end joining and targeted insertion wherein one junction on-target but the other end off-target is commonly present in the knockouts. Protoplast fusion during transformation and regeneration was also a problem. This review will discuss the advantages and technical challenges of gene targeting. Recently, CRISPR-Cas9 is a revolutionary technology and becoming a hot topic in plant gene editing. In the second part of this review, CRISPR-Cas9 technology will be focused on and compared to gene targeting regarding the practical use in Physcomitrella patens. This review presents an updated perspective of the gene targeting and CRISPR-Cas9 techniques to plant biologists who may consider studying gene functions in the model organism Physcomitrella patens.


2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Benjamin M. Nash ◽  
To Ha Loi ◽  
Milan Fernando ◽  
Amin Sabri ◽  
James Robinson ◽  
...  

Human induced pluripotent stem cells (hiPSCs) generated from patients and the derivative retinal cells enable the investigation of pathological and novel variants in relevant cell populations. Biallelic pathogenic variants in RPE65 cause early-onset severe retinal dystrophy (EOSRD) or Leber congenital amaurosis (LCA). Increasingly, regulatory-approved in vivo RPE65 retinal gene replacement therapy is available for patients with these clinical features, but only if they have biallelic pathological variants and sufficient viable retinal cells. In our cohort of patients, we identified siblings with early-onset severe retinal degeneration where genomic studies revealed compound heterozygous variants in RPE65, one a known pathogenic missense variant and the other a novel synonymous variant of uncertain significance. The synonymous variant was suspected to affect RNA splicing. Since RPE65 is very poorly expressed in all tissues except the retinal pigment epithelium (RPE), we generated hiPSC-derived RPE cells from the parental carrier of the synonymous variant. Sequencing of RNA obtained from hiPSC-RPE cells demonstrated heterozygous skipping of RPE65 exon 2 and the introduction of a premature stop codon in the mRNA. Minigene studies confirmed the splicing aberration. Results from this study led to reclassification of the synonymous variant to a pathogenic variant, providing the affected patients with access to RPE65 gene replacement therapy.


2021 ◽  
Author(s):  
Maren Freigang ◽  
Petra Steinacker ◽  
Claudia Diana Wurster ◽  
Olivia Schreiber-Katz ◽  
Alma Osmanovic ◽  
...  

Abstract BackgroundActivated astroglia is involved in the pathophysiology of neurodegenerative diseases and has also been described in animal models of spinal muscular atrophy (SMA). Given the urgent need of biomarkers for treatment monitoring of new RNA-modifying and gene replacement therapies in SMA, we examined glial fibrillary acidic protein (GFAP) concentrations as a marker of astrogliosis in the cerebrospinal fluid (CSF) of children and adult patients with SMA before and during treatment with nusinersen.Methods58 adult patients and 21 children with genetically confirmed 5q-associated SMA from 4 German motor neuron disease specialist care centers and 30 age- and sex-matched controls were prospectively included in this study. GFAP concentration was measured in CSF and motor performance and disease severity were assessed.ResultsCSF GFAP concentrations did not differ from controls but showed higher levels in more severely affected patients after adjustment for patients’ age. Within 14 months of nusinersen treatment, CSF GFAP concentrations did not change significantly.ConclusionsGFAP concentration in CSF of patients with long-standing SMA is not useful to assess disease severity or predict treatment response, but might support the hypothesis that glial activation is involved in SMA pathology.


2021 ◽  
Author(s):  
Sivaraj M Sundaram ◽  
Adriana Arrulo Pereira ◽  
Hannes Köpke ◽  
Helge Müller-Fielitz ◽  
Meri De Angelis ◽  
...  

The solute carrier monocarboxylate transporter 8 (MCT8) transports the thyroid hormones thyroxine and tri-iodothyronine (T3) across cell membranes. MCT8 gene deficiency, termed Allan-Herndon-Dudley syndrome, is an important cause of X-linked intellectual and motor disability. As no treatment of the neurological symptoms is available yet, we tested a gene replacement therapy in Mct8- and Oatp1c1-deficient mice as a well-established model of the disease. Here, we report that targeting brain endothelial cells for Mct8 expression by intravenously injecting the vector AAV-BR1-Mct8 increased T3 levels in the brain and ameliorated morphological and functional parameters associated with the disease. Importantly, the therapy resulted in a long-lasting improvement in motor coordination. Thus, the data support the concept that MCT8 mediates the transport of thyroid hormones into the brain and indicate that a readily accessible vascular target can help overcome the consequences of the severe disability associated with MCT8 deficiency.


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