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Zhang Y, Shi Y, Khan MM, Xiao F, Chen W, Tao W, Yao K, Kong N. Ocular RNA nanomedicine: engineered delivery nanoplatforms in treating eye diseases. Trends Biotechnol 2024:S0167-7799(24)00121-5. [PMID: 38821834 DOI: 10.1016/j.tibtech.2024.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 04/23/2024] [Accepted: 05/06/2024] [Indexed: 06/02/2024]
Abstract
Ocular disorders remain a major global health challenge with unmet medical needs. RNA nanomedicine has shown significant therapeutic benefits and safety profiles in patients with complex eye disorders, already benefiting numerous patients with gene-related eye disorders. The effective delivery of RNA to the unique structure of the eye is challenging owing to RNA instability, off-target effects, and ocular physiological barriers. Specifically tailored RNA medication, coupled with sophisticated engineered delivery platforms, is crucial to guide and advance developments in treatments for oculopathy. Herein we review recent advances in RNA-based nanomedicine, innovative delivery strategies, and current clinical progress and present challenges in ocular disease therapy.
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Affiliation(s)
- Yiming Zhang
- Liangzhu Laboratory, Zhejiang University Medical Center and Zhejiang Provincial Key Lab of Ophthalmology, Eye Center of The Second Affiliated Hospital, Zhejiang University, Hangzhou, China; Center for Nanomedicine and Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Yesi Shi
- Center for Nanomedicine and Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Muhammad M Khan
- Center for Nanomedicine and Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Fan Xiao
- Liangzhu Laboratory, Zhejiang University Medical Center and Zhejiang Provincial Key Lab of Ophthalmology, Eye Center of The Second Affiliated Hospital, Zhejiang University, Hangzhou, China; Center for Nanomedicine and Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Wei Chen
- Center for Nanomedicine and Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Wei Tao
- Center for Nanomedicine and Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
| | - Ke Yao
- Liangzhu Laboratory, Zhejiang University Medical Center and Zhejiang Provincial Key Lab of Ophthalmology, Eye Center of The Second Affiliated Hospital, Zhejiang University, Hangzhou, China.
| | - Na Kong
- Liangzhu Laboratory, Zhejiang University Medical Center and Zhejiang Provincial Key Lab of Ophthalmology, Eye Center of The Second Affiliated Hospital, Zhejiang University, Hangzhou, China; Center for Nanomedicine and Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
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Priglinger CS, Gerhardt MJ, Rudolph G, Priglinger SG, Michalakis S. [Gene therapy in ophthalmology]. DIE OPHTHALMOLOGIE 2023; 120:867-882. [PMID: 37418021 DOI: 10.1007/s00347-023-01883-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/25/2023] [Indexed: 07/08/2023]
Abstract
In 2017 the gene therapy medication voretigene neparvovec-rzyl was approved by the U.S. Food and Drug Administration (FDA) for retinal gene therapy of hereditary retinal dystrophies caused by mutations in the RPE65 gene. Voretigene neparvovec-rzyl is a gene augmentation therapy using an adeno-associated virus-based vector to express a healthy copy of the human RPE65 gene in the patient's retinal pigment epithelial (RPE) cells. The success of gene augmentation therapy in RPE65-linked retinal dystrophy encouraged research activities on the concept of gene supplementation to be extended to nongenetic diseases, such as age-related macular degeneration; however, it also showed that the principle of success cannot be easily extended to other retinal dystrophies. This review article presents the most commonly used principles and technologies of gene therapy and provides an overview of the current challenges and limitations. Furthermore, practice-relevant aspects of the indications and the treatment procedure are discussed. Particular attention is paid to the consideration of disease stages, especially with respect to patient's expectations and the evaluation of treatment success.
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Affiliation(s)
- Claudia S Priglinger
- Augenklinik, Ludwig-Maximilians-Universität München, Mathildenstr. 8, 80336, München, Deutschland.
| | - Maximilian J Gerhardt
- Augenklinik, Ludwig-Maximilians-Universität München, Mathildenstr. 8, 80336, München, Deutschland
| | - Günther Rudolph
- Augenklinik, Ludwig-Maximilians-Universität München, Mathildenstr. 8, 80336, München, Deutschland
| | - Siegfried G Priglinger
- Augenklinik, Ludwig-Maximilians-Universität München, Mathildenstr. 8, 80336, München, Deutschland
| | - Stylianos Michalakis
- Augenklinik, Ludwig-Maximilians-Universität München, Mathildenstr. 8, 80336, München, Deutschland
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3
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Xu P, Jiang YY, Morgan JIW. Cone Photoreceptor Morphology in Choroideremia Assessed Using Non-Confocal Split-Detection Adaptive Optics Scanning Light Ophthalmoscopy. Invest Ophthalmol Vis Sci 2023; 64:36. [PMID: 37504961 PMCID: PMC10383007 DOI: 10.1167/iovs.64.10.36] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 07/10/2023] [Indexed: 07/29/2023] Open
Abstract
Purpose Choroideremia (CHM) is an X-linked inherited retinal degeneration causing loss of the photoreceptors, retinal pigment epithelium, and choriocapillaris, although patients typically retain a central island of relatively preserved, functioning retina until late-stage disease. Here, we investigate cone photoreceptor morphology within the retained retinal island by examining cone inner segment area, density, circularity, and intercone space. Methods Using a custom-built, multimodal adaptive optics scanning light ophthalmoscope, nonconfocal split-detection images of the photoreceptor mosaic were collected at 1°, 2°, and 4° temporal to the fovea from 13 CHM and 12 control subjects. Cone centers were manually identified, and cone borders were segmented. A custom MATLAB script was used to extract area and circularity for each cone and calculate the percentage of intercone space in each region of interest. Bound cone density was also calculated. An unbalanced two-way ANOVA and Bonferroni post hoc tests were used to assess statistical differences between the CHM and control groups and along retinal eccentricity. Results Cone density was lower in the CHM group than in the control group (P < 0.001) and decreased with eccentricity from the fovea (P < 0.001). CHM cone inner segments were larger in area (P < 0.001) and more circular (P = 0.042) than those of the controls. Intercone space in CHM was also higher than in the controls (P < 0.001). Conclusions Cone morphology is altered in CHM compared to control, even within the centrally retained, functioning retinal area. Further studies are required to determine whether such morphology is a precursor to cone degeneration.
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Affiliation(s)
- Peiluo Xu
- Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Yu You Jiang
- Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania, United States
- Center for Advanced Retinal and Ocular Therapeutics, University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Jessica I. W. Morgan
- Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania, United States
- Center for Advanced Retinal and Ocular Therapeutics, University of Pennsylvania, Philadelphia, Pennsylvania, United States
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Hashida N, Nishida K. Recent advances and future prospects: current status and challenges of the intraocular injection of drugs for vitreoretinal diseases. Adv Drug Deliv Rev 2023; 198:114870. [PMID: 37172783 DOI: 10.1016/j.addr.2023.114870] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 04/07/2023] [Accepted: 05/07/2023] [Indexed: 05/15/2023]
Abstract
Effective drug therapy for vitreoretinal disease is a major challenge in the field of ophthalmology; various protective systems, including anatomical and physiological barriers, complicate drug delivery to precise targets. However, as the eye is a closed cavity, it is an ideal target for local administration. Various types of drug delivery systems have been investigated that take advantage of this aspect of the eye, enhancing ocular permeability and optimizing local drug concentrations. Many drugs, mainly anti-VEGF drugs, have been evaluated in clinical trials and have provided clinical benefit to many patients. In the near future, innovative drug delivery systems will be developed to avoid frequent intravitreal administration of drugs and maintain effective drug concentrations for a long period of time. Here, we review the published literature on various drugs and administration routes and current clinical applications. Recent advances in drug delivery systems are discussed along with future prospects.
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Affiliation(s)
- Noriyasu Hashida
- Department of Ophthalmology, Osaka University Graduate School of Medicine, Osaka, Japan.
| | - Kohji Nishida
- Department of Ophthalmology, Osaka University Graduate School of Medicine, Osaka, Japan; Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives (OTRI), Osaka University Graduate School of Medicine, Osaka, Japan
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Zaman H, Khan A, Khan K, Toheed S, Abdullah M, Zeeshan HM, Hameed A, Umar M, Shahid M, Malik K, Afzal S. Adeno-Associated Virus-Mediated Gene Therapy. Crit Rev Eukaryot Gene Expr 2023; 33:87-100. [PMID: 37522547 DOI: 10.1615/critreveukaryotgeneexpr.2023048135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/01/2023]
Abstract
Choice of vector is the most critical step in gene therapy. Adeno-associated viruses (AAV); third generation vectors, are getting much attention of scientists to be used as vehicles due to their non-pathogenicity, excellent safety profile, low immune responses, great efficiency to transduce non-dividing cells, large capacity to transfer genetic material and long-term expression of genetic payload. AAVs have multiple serotypes and each serotype shows tropism for a specific cell. Different serotypes are used to target liver, lungs, muscles, retina, heart, CNS, kidneys, etc. Furthermore, AAV based gene therapies have tremendous marketing applications that can be perfectly incorporated in the anticipated sites of the host target genome resulting in life long expression of transgenes. Some therapeutic products use AAV vectors that are used to treat lipoprotein lipase deficiency (LPLD) and it is injected intramuscularly, to treat mutated retinal pigment epithelium RPE65 (RPE65) that is introduced to subretinal space, an intravenous infusion to treat spinal muscular atrophy and rAAV2-CFTR vector is introduced into nasal epithelial cells to treat cystic fibrosis. AAV therapies and other such interdisciplinary methodologies can create the miracles for the generation of precision gene therapies for the treatment of most serious and sometimes fatal disorders.
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Affiliation(s)
- Hassan Zaman
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Aakif Khan
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Khalid Khan
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Shazma Toheed
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Muhammad Abdullah
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | | | - Abdul Hameed
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Muhammad Umar
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Muhammad Shahid
- Division of Molecular Virology and Infectious Diseases, Center of Excellence in Molecular Biology (CEMB), 87-West Canal Bank Road Thokar Niaz Baig, University of the Punjab, Lahore, Pakistan
| | - Kausar Malik
- Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan
| | - Samia Afzal
- Center of Excellence in Molecular Biology (CEMB), 87-West Canal Bank Road Thokar Niaz Baig, University of the Punjab, Lahore, Pakistan
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Nanegrungsunk O, Au A, Sarraf D, Sadda SR. New frontiers of retinal therapeutic intervention: a critical analysis of novel approaches. Ann Med 2022; 54:1067-1080. [PMID: 35467460 PMCID: PMC9045775 DOI: 10.1080/07853890.2022.2066169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A recent wave of pharmacologic and technologic innovations has revolutionized our management of retinal diseases. Many of these advancements have demonstrated efficacy and can increase the quality of life while potentially reducing complications and decreasing the burden of care for patients. Some advances, such as longer-acting anti-vascular endothelial growth factor agents, port delivery systems, gene therapy, and retinal prosthetics have been approved by the US Food and Drug Administration, and are available for clinical use. Countless other therapeutics are in various stages of development, promising a bright future for further improvements in the management of the retinal disease. Herein, we have highlighted several important novel therapies and therapeutic approaches and examine the opportunities and limitations offered by these innovations at the new frontier. KEY MESSAGESNumerous pharmacologic and technologic advancements have been emerging, providing a higher treatment efficacy while decreasing the burden and associated side effects.Anti-vascular endothelial growth factor (anti-VEGF) and its longer-acting agents have dramatically improved visual outcomes and have become a mainstay treatment in various retinal diseases.Gene therapy and retinal prosthesis implantation in the treatment of congenital retinal dystrophy can accomplish the partial restoration of vision and improved daily function in patients with blindness, an unprecedented success in the field of retina.
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Affiliation(s)
- Onnisa Nanegrungsunk
- Doheny Eye Institute, Pasadena, CA, USA.,Department of Ophthalmology, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA, USA.,Retina Division, Department of Ophthalmology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Adrian Au
- Stein Eye Institute, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA, USA
| | - David Sarraf
- Stein Eye Institute, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA, USA
| | - Srinivas R Sadda
- Doheny Eye Institute, Pasadena, CA, USA.,Department of Ophthalmology, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, CA, USA
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Wang JH, Lidgerwood GE, Daniszewski M, Hu ML, Roberts GE, Wong RCB, Hung SSC, McClements ME, Hewitt AW, Pébay A, Hickey DG, Edwards TL. AAV2-mediated gene therapy for Bietti crystalline dystrophy provides functional CYP4V2 in multiple relevant cell models. Sci Rep 2022; 12:9525. [PMID: 35680963 PMCID: PMC9184470 DOI: 10.1038/s41598-022-12210-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 04/06/2022] [Indexed: 12/23/2022] Open
Abstract
Bietti crystalline dystrophy (BCD) is an inherited retinal disease (IRD) caused by mutations in the CYP4V2 gene. It is a relatively common cause of IRD in east Asia. A number of features of this disease make it highly amenable to gene supplementation therapy. This study aims to validate a series of essential precursor in vitro experiments prior to developing a clinical gene therapy for BCD. We demonstrated that HEK293, ARPE19, and patient induced pluripotent stem cell (iPSC)-derived RPE cells transduced with AAV2 vectors encoding codon optimization of CYP4V2 (AAV2.coCYP4V2) resulted in elevated protein expression levels of CYP4V2 compared to those transduced with AAV2 vectors encoding wild type CYP4V2 (AAV2.wtCYP4V2), as assessed by immunocytochemistry and western blot. Similarly, we observed significantly increased CYP4V2 enzyme activity in cells transduced with AAV2.coCYP4V2 compared to those transduced with AAV2.wtCYP4V2. We also showed CYP4V2 expression in human RPE/choroid explants transduced with AAV2.coCYP4V2 compared to those transduced with AAV2.wtCYP4V2. These preclinical data support the further development of a gene supplementation therapy for a currently untreatable blinding condition—BCD. Codon-optimized CYP4V2 transgene was superior to wild type in terms of protein expression and enzyme activity. Ex vivo culture of human RPE cells provided an effective approach to test AAV-mediated transgene delivery.
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Affiliation(s)
- Jiang-Hui Wang
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Level 7, 32 Gisborne Street, East Melbourne, VIC, 3002, Australia
| | - Grace E Lidgerwood
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Level 7, 32 Gisborne Street, East Melbourne, VIC, 3002, Australia.,Department of Anatomy and Physiology, The University of Melbourne, Parkville, Australia
| | - Maciej Daniszewski
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, Australia
| | - Monica L Hu
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Level 7, 32 Gisborne Street, East Melbourne, VIC, 3002, Australia
| | - Georgina E Roberts
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Level 7, 32 Gisborne Street, East Melbourne, VIC, 3002, Australia
| | - Raymond C B Wong
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Level 7, 32 Gisborne Street, East Melbourne, VIC, 3002, Australia.,Ophthalmology, Department of Surgery, The University of Melbourne, East Melbourne, VIC, Australia.,Shenzhen Eye Hospital, Shenzhen University School of Medicine, Shenzhen, China
| | - Sandy S C Hung
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Level 7, 32 Gisborne Street, East Melbourne, VIC, 3002, Australia.,Ophthalmology, Department of Surgery, The University of Melbourne, East Melbourne, VIC, Australia
| | - Michelle E McClements
- Department of Clinical Neurosciences, Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, UK
| | - Alex W Hewitt
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Level 7, 32 Gisborne Street, East Melbourne, VIC, 3002, Australia.,Ophthalmology, Department of Surgery, The University of Melbourne, East Melbourne, VIC, Australia.,Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Alice Pébay
- Department of Anatomy and Physiology, The University of Melbourne, Parkville, Australia.,Department of Surgery, Royal Melbourne Hospital, The University of Melbourne, Parkville, Australia
| | - Doron G Hickey
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Level 7, 32 Gisborne Street, East Melbourne, VIC, 3002, Australia
| | - Thomas L Edwards
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Level 7, 32 Gisborne Street, East Melbourne, VIC, 3002, Australia. .,Ophthalmology, Department of Surgery, The University of Melbourne, East Melbourne, VIC, Australia.
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Amato A, Arrigo A, Aragona E, Manitto MP, Saladino A, Bandello F, Battaglia Parodi M. Gene Therapy in Inherited Retinal Diseases: An Update on Current State of the Art. Front Med (Lausanne) 2021; 8:750586. [PMID: 34722588 PMCID: PMC8553993 DOI: 10.3389/fmed.2021.750586] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/20/2021] [Indexed: 12/11/2022] Open
Abstract
Background: Gene therapy cannot be yet considered a far perspective, but a tangible therapeutic option in the field of retinal diseases. Although still confined in experimental settings, the preliminary results are promising and provide an overall scenario suggesting that we are not so far from the application of gene therapy in clinical settings. The main aim of this review is to provide a complete and updated overview of the current state of the art and of the future perspectives of gene therapy applied on retinal diseases. Methods: We carefully revised the entire literature to report all the relevant findings related to the experimental procedures and the future scenarios of gene therapy applied in retinal diseases. A clinical background and a detailed description of the genetic features of each retinal disease included are also reported. Results: The current literature strongly support the hope of gene therapy options developed for retinal diseases. Although being considered in advanced stages of investigation for some retinal diseases, such as choroideremia (CHM), retinitis pigmentosa (RP), and Leber's congenital amaurosis (LCA), gene therapy is still quite far from a tangible application in clinical practice for other retinal diseases. Conclusions: Gene therapy is an extremely promising therapeutic tool for retinal diseases. The experimental data reported in this review offer a strong hope that gene therapy will be effectively available in clinical practice in the next years.
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Affiliation(s)
- Alessia Amato
- Department of Ophthalmology, Scientific Institute San Raffaele Hospital, Milan, Italy
| | - Alessandro Arrigo
- Department of Ophthalmology, Scientific Institute San Raffaele Hospital, Milan, Italy
| | - Emanuela Aragona
- Department of Ophthalmology, Scientific Institute San Raffaele Hospital, Milan, Italy
| | - Maria Pia Manitto
- Department of Ophthalmology, Scientific Institute San Raffaele Hospital, Milan, Italy
| | - Andrea Saladino
- Department of Ophthalmology, Scientific Institute San Raffaele Hospital, Milan, Italy
| | - Francesco Bandello
- Department of Ophthalmology, Scientific Institute San Raffaele Hospital, Milan, Italy
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Molecular Characterization of Choroideremia-Associated Deletions Reveals an Unexpected Regulation of CHM Gene Transcription. Genes (Basel) 2021; 12:genes12081111. [PMID: 34440285 PMCID: PMC8392058 DOI: 10.3390/genes12081111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 07/16/2021] [Accepted: 07/19/2021] [Indexed: 12/03/2022] Open
Abstract
Choroideremia (CHM) is a X-linked recessive chorioretinal dystrophy due to deficiency of the CHM gene product, i.e., Rab escort protein isoform 1 (REP1). To date, gene therapy for CHM has shown variable effectiveness, likely because the underlying pathogenic mechanisms as well as genotype-phenotype correlation are not yet fully known. Small nucleotide variants leading to premature termination codons (PTCs) are a major cause of CHM, but about 20% of patients has CHM gene deletions. To improve understanding of the disease mechanisms, we analyzed molecular features of seven deletions involving the CHM gene sequence. We mapped the deletion breakpoints by using polymerase chain reaction, sequencing and array comparative genomic hybridization; to identify rearrangement-promoting DNA sequences, we analyzed genomic architecture surrounding the breakpoint regions. Moreover, in some CHM patients with different mutation types, we measured transcript level of CHM and of CHML, encoding the REP2 isoform. Scattered along the whole CHM gene and in close proximity to the deletion breakpoints we found numerous repeat elements that generate a locus-specific rearrangement hot spot. Unexpectedly, patients with non-PTC variants had increased expression of the aberrant CHM mRNA; CHML expression was higher than normal in a patient lacking CHM and its putative regulatory sequences. This latest evidence suggests that mechanisms regulating CHM and CHML gene expression are worthy of further study, because their full knowledge could be also useful for developing effective therapies for this hitherto untreatable inherited retinal degeneration.
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