1
|
Moraes CT. Tools for editing the mammalian mitochondrial genome. Hum Mol Genet 2024; 33:R92-R99. [PMID: 38779768 DOI: 10.1093/hmg/ddae037] [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: 01/17/2024] [Revised: 02/28/2024] [Accepted: 03/03/2024] [Indexed: 05/25/2024] Open
Abstract
The manipulation of animal mitochondrial genomes has long been a challenge due to the lack of an effective transformation method. With the discovery of specific gene editing enzymes, designed to target pathogenic mitochondrial DNA mutations (often heteroplasmic), the selective removal or modification of mutant variants has become a reality. Because mitochondria cannot efficiently import RNAs, CRISPR has not been the first choice for editing mitochondrial genes. However, the last few years witnessed an explosion in novel and optimized non-CRISPR approaches to promote double-strand breaks or base-edit of mtDNA in vivo. Engineered forms of specific nucleases and cytidine/adenine deaminases form the basis for these techniques. I will review the newest developments that constitute the current toolbox for animal mtDNA gene editing in vivo, bringing these approaches not only to the exploration of mitochondrial function, but also closer to clinical use.
Collapse
Affiliation(s)
- Carlos T Moraes
- Miller School of Medicine, University of Miami, 1600 NW 10th Ave, room 7044, Miami, FL 33136, United States
| |
Collapse
|
2
|
Castillo SR, Simone BW, Clark KJ, Devaux P, Ekker SC. Unconstrained Precision Mitochondrial Genome Editing with αDdCBEs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.13.593977. [PMID: 38798498 PMCID: PMC11118498 DOI: 10.1101/2024.05.13.593977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
DddA-derived cytosine base editors (DdCBEs) enable the targeted introduction of C•G-to-T•A conversions in mitochondrial DNA (mtDNA). DdCBEs are often deployed as pairs, with each arm comprised of a transcription activator-like effector (TALE), a split double-stranded DNA deaminase half, and a uracil glycosylase inhibitor. This pioneering technology has helped improve our understanding of cellular processes involving mtDNA and has paved the way for the development of models and therapies for genetic disorders caused by pathogenic mtDNA variants. Nonetheless, given the intrinsic properties of TALE proteins, several target sites in human mtDNA remain out of reach to DdCBEs and other TALE-based technologies. Specifically, due to the conventional requirement for a thymine immediately upstream of the TALE target sequences (i.e., the 5'-T constraint), over 150 loci in the human mitochondrial genome are presumed to be inaccessible to DdCBEs. Previous attempts at circumventing this constraint, either by developing monomeric DdCBEs or utilizing DNA-binding domains alternative to TALEs, have resulted in suboptimal specificity profiles with reduced therapeutic potential. Here, aiming to challenge and elucidate the relevance of the 5'-T constraint in the context of DdCBE-mediated mtDNA editing, and to expand the range of motifs that are editable by this technology, we generated αDdCBEs that contain modified TALE proteins engineered to recognize all 5' bases. Notably, 5'-T-noncompliant, canonical DdCBEs efficiently edited mtDNA at diverse loci. However, DdCBEs were frequently outperformed by αDdCBEs, which consistently displayed significant improvements in activity and specificity, regardless of the 5'-most bases of their TALE binding sites. Furthermore, we showed that αDdCBEs are compatible with DddA tox and its derivatives DddA6, and DddA11, and we validated TALE shifting with αDdCBEs as an effective approach to optimize base editing outcomes at a single target site. Overall, αDdCBEs enable efficient, specific, and unconstrained mitochondrial base editing.
Collapse
|
3
|
Eghbalsaied S, Lawler C, Petersen B, Hajiyev RA, Bischoff SR, Frankenberg S. CRISPR/Cas9-mediated base editors and their prospects for mitochondrial genome engineering. Gene Ther 2024; 31:209-223. [PMID: 38177342 DOI: 10.1038/s41434-023-00434-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 12/05/2023] [Accepted: 12/07/2023] [Indexed: 01/06/2024]
Abstract
Base editors are a type of double-stranded break (DSB)-free gene editing technology that has opened up new possibilities for precise manipulation of mitochondrial DNA (mtDNA). This includes cytosine and adenosine base editors and more recently guanosine base editors. Because of having low off-target and indel rates, there is a growing interest in developing and evolving this research field. Here, we provide a detailed update on DNA base editors. While base editing has widely been used for nuclear genome engineering, the growing interest in applying this technology to mitochondrial DNA has been faced with several challenges. While Cas9 protein has been shown to enter mitochondria, use of smaller Cas proteins, such as Cas12a, has higher import efficiency. However, sgRNA transfer into mitochondria is the most challenging step. sgRNA structure and ratio of Cas protein to sgRNA are both important factors for efficient sgRNA entry into mitochondria. In conclusion, while there are still several challenges to be addressed, ongoing research in this field holds the potential for new treatments and therapies for mitochondrial disorders.
Collapse
Affiliation(s)
- Shahin Eghbalsaied
- School of BioSciences, The University of Melbourne, Parkville, VIC, Australia.
- Department of Animal Science, Isfahan Branch, Islamic Azad University (IAU), Isfahan, Iran.
- Department of Cardiology and Pneumology, University Medical Center Göttingen, Göttingen, Germany.
| | - Clancy Lawler
- School of BioSciences, The University of Melbourne, Parkville, VIC, Australia
| | - Björn Petersen
- Department of Biotechnology, Institute of Farm Animal Genetics, Friedrich-Loeffler-Institute (FLI), Mariensee, Germany
- eGenesis, 2706 HWY E, 53572, Mount Horeb, WI, USA
| | - Raul A Hajiyev
- Department of Genome Engineering, NovoHelix, Miami, FL, USA
- Department of Computer Science, Kent State University, Kent, OH, USA
| | - Steve R Bischoff
- Department of Genome Engineering, NovoHelix, Miami, FL, USA
- Foundry for Genome Engineering & Reproductive Medicine (FGERM), Miami, FL, USA
| | - Stephen Frankenberg
- School of BioSciences, The University of Melbourne, Parkville, VIC, Australia.
| |
Collapse
|
4
|
Zhou C, Okuno M, Nakazato I, Tsutsumi N, Arimura SI. Targeted A-to-G base editing in the organellar genomes of Arabidopsis with monomeric programmable deaminases. PLANT PHYSIOLOGY 2024; 194:2278-2287. [PMID: 38128544 PMCID: PMC10980515 DOI: 10.1093/plphys/kiad678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 11/29/2023] [Accepted: 12/06/2023] [Indexed: 12/23/2023]
Abstract
Plastids and mitochondria are 2 intracellular organelles containing DNA-encoding partial but essential components for their roles, photosynthesis, and respiration. Precise base editing in both plastid and mitochondrial genomes would benefit their gene functional analysis and crop breeding. Targeted base editing in organellar genomes relies on a protein-based genome-editing system that uses the TALE-DNA recognition motif with deaminases. This is because the efficient delivery of guide RNA for clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 systems into organelles is currently impossible. Since TALE-based base editors used in organellar genomes are usually dimeric types, in this study, we used targeted A-to-G base editing in Arabidopsis (Arabidopsis thaliana) plastid and mitochondrial genomes with monomeric TALE-based deaminase for easier assembling of vectors. As a result, inheritable targeted A-to-G base editing of adenosine triphosphatase subunit 6-2 (atp6-2) in plant mitochondrial genomes and of 16S ribosomal RNA (16S rRNA) in plastid genomes of Arabidopsis was successfully induced by monomeric TALE-based adenine deaminase (AD) without off-target mutations. The monomeric TALE-based adenine deaminases also demonstrated a preference for editing the 8th T on the same strand from the recognition end. Phenotypic analysis showed that A-to-G conversion at 1139A of plastid 16S rRNA conferred substantial spectinomycin resistance in Arabidopsis, but not the other 2 potential-resistant mutations at 1131T and 1137T, predicted from the previous bacterial data. Our study demonstrated the feasibility of monomeric TALE-based ADs in plant organelles and their potential contribution to the functional analyses of plant organelles with easier assembling.
Collapse
Affiliation(s)
- Chang Zhou
- Laboratory of Plant Molecular Genetics, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Miki Okuno
- Division of Microbiology, Department of Infectious Medicine, Kurume University School of Medicine, Fukuoka 830-0011, Japan
| | - Issei Nakazato
- Laboratory of Plant Molecular Genetics, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
- Research Fellow of Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083, Japan
| | - Nobuhiro Tsutsumi
- Laboratory of Plant Molecular Genetics, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Shin-ichi Arimura
- Laboratory of Plant Molecular Genetics, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| |
Collapse
|
5
|
Nikitchina N, Ulashchik E, Shmanai V, Heckel AM, Tarassov I, Mazunin I, Entelis N. Targeting of CRISPR-Cas12a crRNAs into human mitochondria. Biochimie 2024; 217:74-85. [PMID: 37690471 DOI: 10.1016/j.biochi.2023.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 08/10/2023] [Accepted: 09/04/2023] [Indexed: 09/12/2023]
Abstract
Mitochondrial gene editing holds great promise as a therapeutic approach for mitochondrial diseases caused by mutations in the mitochondrial DNA (mtDNA). Current strategies focus on reducing mutant mtDNA heteroplasmy levels through targeted cleavage or base editing. However, the delivery of editing components into mitochondria remains a challenge. Here we investigate the import of CRISPR-Cas12a system guide RNAs (crRNAs) into human mitochondria and study the structural requirements for this process by northern blot analysis of RNA isolated from nucleases-treated mitoplasts. To investigate whether the fusion of crRNA with known RNA import determinants (MLS) improve its mitochondrial targeting, we added MLS hairpin structures at 3'-end of crRNA and demonstrated that this did not impact crRNA ability to program specific cleavage of DNA in lysate of human cells expressing AsCas12a nuclease. Surprisingly, mitochondrial localization of the fused crRNA molecules was not improved compared to non-modified version, indicating that structured scaffold domain of crRNA can probably function as MLS, assuring crRNA mitochondrial import. Then, we designed a series of crRNAs targeting different regions of mtDNA and demonstrated their ability to program specific cleavage of mtDNA fragments in cell lysate and their partial localization in mitochondrial matrix in human cells transfected with these RNA molecules. We hypothesize that mitochondrial import of crRNAs may depend on their secondary structure/sequence. We presume that imported crRNA allow reconstituting the active crRNA/Cas12a system in human mitochondria, which can contribute to the development of effective strategies for mitochondrial gene editing and potential future treatment of mitochondrial diseases.
Collapse
Affiliation(s)
- Natalia Nikitchina
- UMR7156 - Molecular Genetics, Genomics, Microbiology, University of Strasbourg, Strasbourg, 67000, France
| | - Egor Ulashchik
- Institute of Physical Organic Chemistry, National Academy of Science of Belarus, Minsk, 220072, Belarus
| | - Vadim Shmanai
- Institute of Physical Organic Chemistry, National Academy of Science of Belarus, Minsk, 220072, Belarus
| | - Anne-Marie Heckel
- UMR7156 - Molecular Genetics, Genomics, Microbiology, University of Strasbourg, Strasbourg, 67000, France
| | - Ivan Tarassov
- UMR7156 - Molecular Genetics, Genomics, Microbiology, University of Strasbourg, Strasbourg, 67000, France
| | - Ilya Mazunin
- Center for Molecular and Cellular Biology, Skolkovo Institute of Science and Technology, Moscow, 143026, Russia
| | - Nina Entelis
- UMR7156 - Molecular Genetics, Genomics, Microbiology, University of Strasbourg, Strasbourg, 67000, France.
| |
Collapse
|
6
|
Keshavan N, Minczuk M, Viscomi C, Rahman S. Gene therapy for mitochondrial disorders. J Inherit Metab Dis 2024; 47:145-175. [PMID: 38171948 DOI: 10.1002/jimd.12699] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 10/30/2023] [Accepted: 11/30/2023] [Indexed: 01/05/2024]
Abstract
In this review, we detail the current state of application of gene therapy to primary mitochondrial disorders (PMDs). Recombinant adeno-associated virus-based (rAAV) gene replacement approaches for nuclear gene disorders have been undertaken successfully in more than ten preclinical mouse models of PMDs which has been made possible by the development of novel rAAV technologies that achieve more efficient organ targeting. So far, however, the greatest progress has been made for Leber Hereditary Optic Neuropathy, for which phase 3 clinical trials of lenadogene nolparvovec demonstrated efficacy and good tolerability. Other methods of treating mitochondrial DNA (mtDNA) disorders have also had traction, including refinements to nucleases that degrade mtDNA molecules with pathogenic variants, including transcription activator-like effector nucleases, zinc-finger nucleases, and meganucleases (mitoARCUS). rAAV-based approaches have been used successfully to deliver these nucleases in vivo in mice. Exciting developments in CRISPR-Cas9 gene editing technology have achieved in vivo gene editing in mouse models of PMDs due to nuclear gene defects and new CRISPR-free gene editing approaches have shown great potential for therapeutic application in mtDNA disorders. We conclude the review by discussing the challenges of translating gene therapy in patients both from the point of view of achieving adequate organ transduction as well as clinical trial design.
Collapse
Affiliation(s)
- Nandaki Keshavan
- UCL Great Ormond Street Institute of Child Health, London, UK
- Great Ormond Street Hospital, London, UK
| | - Michal Minczuk
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, UK
| | - Carlo Viscomi
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Veneto Institute of Molecular Medicine (VIMM), Padova, Italy
| | - Shamima Rahman
- UCL Great Ormond Street Institute of Child Health, London, UK
- Great Ormond Street Hospital, London, UK
| |
Collapse
|
7
|
Kim JS, Chen J. Base editing of organellar DNA with programmable deaminases. Nat Rev Mol Cell Biol 2024; 25:34-45. [PMID: 37794167 DOI: 10.1038/s41580-023-00663-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2023] [Indexed: 10/06/2023]
Abstract
Mitochondria and chloroplasts are organelles that include their own genomes, which encode key genes for ATP production and carbon dioxide fixation, respectively. Mutations in mitochondrial DNA can cause diverse genetic disorders and are also linked to ageing and age-related diseases, including cancer. Targeted editing of organellar DNA should be useful for studying organellar genes and developing novel therapeutics, but it has been hindered by lack of efficient tools in living cells. Recently, CRISPR-free, protein-only base editors, such as double-stranded DNA deaminase toxin A-derived cytosine base editors (DdCBEs) and adenine base editors (ABEs), have been developed, which enable targeted organellar DNA editing in human cell lines, animals and plants. In this Review, we present programmable deaminases developed for base editing of organellar DNA in vitro and discuss mitochondrial DNA editing in animals, and plastid genome (plastome) editing in plants. We also discuss precision and efficiency limitations of these tools and propose improvements for therapeutic, agricultural and environmental applications.
Collapse
Affiliation(s)
- Jin-Soo Kim
- NUS Synthetic Biology for Clinical & Technological Innovation (SynCTI) and Department of Biochemistry, National University of Singapore, Singapore, Singapore.
- Edgene, Seoul, South Korea.
| | - Jia Chen
- Gene Editing Center, School of Life Science and Technology, ShanghaiTech University, Shanghai, China.
- Shanghai Clinical Research and Trial Center, Shanghai, China.
| |
Collapse
|
8
|
Hao Z, Chen J, Sun P, Chen L, Zhang Y, Chen W, Hu D, Bi F, Han Z, Tang X, Suo J, Suo X, Liu X. Distinct non-synonymous mutations in cytochrome b highly correlate with decoquinate resistance in apicomplexan parasite Eimeria tenella. Parasit Vectors 2023; 16:365. [PMID: 37848977 PMCID: PMC10583425 DOI: 10.1186/s13071-023-05988-7] [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: 07/16/2023] [Accepted: 09/28/2023] [Indexed: 10/19/2023] Open
Abstract
BACKGROUND Protozoan parasites of the genus Eimeria are the causative agents of chicken coccidiosis. Parasite resistance to most anticoccidial drugs is one of the major challenges to controlling this disease. There is an urgent need for a molecular marker to monitor the emergence of resistance against anticoccidial drugs, such as decoquinate. METHODS We developed decoquinate-resistant strains by successively exposing the Houghton (H) and Xinjiang (XJ) strains of E. tenella to incremental concentrations of this drug in chickens. Additionally, we isolated a decoquinate-resistant strain from the field. The resistance of these three strains was tested using the criteria of weight gain, relative oocyst production and reduction of lesion scores. Whole-genome sequencing was used to identify the non-synonymous mutations in coding genes that were highly associated with the decoquinate-resistant phenotype in the two laboratory-induced strains. Subsequently, we scrutinized the missense mutation in a field-resistant strain for verification. We also employed the AlphaFold and PyMOL systems to model the alterations in the binding affinity of the mutants toward the drug molecule. RESULTS We obtained two decoquinate-resistant (DecR) strains, DecR_H and XJ, originating from the original H and XJ strains, respectively, as well as a decoquinate-resistant E. tenella strain from the field (DecR_SC). These three strains displayed resistance to 120 mg/kg decoquinate administered through feed. Through whole-genome sequencing analysis, we identified the cytochrome b gene (cyt b; ETH2_MIT00100) as the sole mutated gene shared between the DecR_H and XJ strains and also detected this gene in the DecR_SC strain. Distinct non-synonymous mutations, namely Gln131Lys in DecR_H, Phe263Leu in DecR_XJ, and Phe283Leu in DecR_SC were observed in the three resistant strains. Notably, these mutations were located in the extracellular segments of cyt b, in close proximity to the ubiquinol oxidation site Qo. Drug molecular docking studies revealed that cyt b harboring these mutants exhibited varying degrees of reduced binding ability to decoquinate. CONCLUSIONS Our findings emphasize the critical role of cyt b mutations in the development of decoquinate resistance in E. tenella. The strong correlation observed between cyt b mutant alleles and resistance indicates their potential as valuable molecular markers for the rapid detection of decoquinate resistance.
Collapse
Affiliation(s)
- Zhenkai Hao
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Junmin Chen
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Pei Sun
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Linlin Chen
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Yuanyuan Zhang
- Key Laboratory of Animal Genetics, Breeding and Reproduction of the Ministry of Agriculture & Beijing Key Laboratory of Animal Genetics Improvement, China Agricultural University, Beijing, China
| | - Wenxuan Chen
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Dandan Hu
- School of Animal Science and Technology, Guangxi University, Guangxi, China
| | - Feifei Bi
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Zhenyan Han
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Xinming Tang
- Key Laboratory of Animal Biosafety Risk Prevention and Control (North) of MARA, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Jingxia Suo
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Xun Suo
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Xianyong Liu
- National Key Laboratory of Veterinary Public Health and Safety, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, National Animal Protozoa Laboratory & College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
| |
Collapse
|
9
|
Dewey RE, Selote D, Griffin HC, Dickey AN, Jantz D, Smith JJ, Matthiadis A, Strable J, Kestell C, Smith WA. Cytoplasmic male sterility and abortive seed traits generated through mitochondrial genome editing coupled with allotopic expression of atp1 in tobacco. FRONTIERS IN PLANT SCIENCE 2023; 14:1253640. [PMID: 37780496 PMCID: PMC10541219 DOI: 10.3389/fpls.2023.1253640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 08/29/2023] [Indexed: 10/03/2023]
Abstract
Allotopic expression is the term given for the deliberate relocation of gene function from an organellar genome to the nuclear genome. We hypothesized that the allotopic expression of an essential mitochondrial gene using a promoter that expressed efficiently in all cell types except those responsible for male reproduction would yield a cytoplasmic male sterility (CMS) phenotype once the endogenous mitochondrial gene was inactivated via genome editing. To test this, we repurposed the mitochondrially encoded atp1 gene of tobacco to function in the nucleus under the transcriptional control of a CaMV 35S promoter (construct 35S:nATP1), a promoter that has been shown to be minimally expressed in early stages of anther development. The endogenous atp1 gene was eliminated (Δatp1) from 35S:nATP1 tobacco plants using custom-designed meganucleases directed to the mitochondria. Vegetative growth of most 35S:nATP1/Δatp1 plants appeared normal, but upon flowering produced malformed anthers that failed to shed pollen. When 35S:nATP1/Δatp1 plants were cross-pollinated, ovary/capsule development appeared normal, but the vast majority of the resultant seeds were small, largely hollow and failed to germinate, a phenotype akin to the seedless trait known as stenospermocarpy. Characterization of the mitochondrial genomes from three independent Δatp1 events suggested that spontaneous recombination over regions of microhomology and substoichiometric shifting were the mechanisms responsible for atp1 elimination and genome rearrangement in response to exposure to the atp1-targeting meganucleases. Should the results reported here in tobacco prove to be translatable to other crop species, then multiple applications of allotopic expression of an essential mitochondrial gene followed by its elimination through genome editing can be envisaged. Depending on the promoter(s) used to drive the allotopic gene, this technology may have potential application in the areas of: (1) CMS trait development for use in hybrid seed production; (2) seedless fruit production; and (3) transgene containment.
Collapse
Affiliation(s)
- Ralph E. Dewey
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, United States
| | - Devarshi Selote
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, United States
| | - H. Carol Griffin
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, United States
| | - Allison N. Dickey
- Bioinformatics Research Center, North Carolina State University, Raleigh, NC, United States
| | - Derek Jantz
- Precision BioSciences, Durham, NC, United States
| | | | | | - Josh Strable
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, United States
| | - Caitlin Kestell
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, United States
| | - William A. Smith
- Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC, United States
| |
Collapse
|
10
|
Plascencia-Villa G, Perry G. Exploring Molecular Targets for Mitochondrial Therapies in Neurodegenerative Diseases. Int J Mol Sci 2023; 24:12486. [PMID: 37569861 PMCID: PMC10419704 DOI: 10.3390/ijms241512486] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 07/27/2023] [Accepted: 07/31/2023] [Indexed: 08/13/2023] Open
Abstract
The progressive deterioration of function and structure of brain cells in neurodegenerative diseases is accompanied by mitochondrial dysfunction, affecting cellular metabolism, intracellular signaling, cell differentiation, morphogenesis, and the activation of programmed cell death. However, most of the efforts to develop therapies for Alzheimer's and Parkinson's disease have focused on restoring or maintaining the neurotransmitters in affected neurons, removing abnormal protein aggregates through immunotherapies, or simply treating symptomatology. However, none of these approaches to treating neurodegeneration can stop or reverse the disease other than by helping to maintain mental function and manage behavioral symptoms. Here, we discuss alternative molecular targets for neurodegeneration treatments that focus on mitochondrial functions, including regulation of calcium ion (Ca2+) transport, protein modification, regulation of glucose metabolism, antioxidants, metal chelators, vitamin supplementation, and mitochondrial transference to compromised neurons. After pre-clinical evaluation and studies in animal models, some of these therapeutic compounds have advanced to clinical trials and are expected to have positive outcomes in subjects with neurodegeneration. These mitochondria-targeted therapeutic agents are an alternative to established or conventional molecular targets that have shown limited effectiveness in treating neurodegenerative diseases.
Collapse
Affiliation(s)
- Germán Plascencia-Villa
- Department of Neuroscience, Developmental and Regenerative Biology, The University of Texas at San Antonio (UTSA), San Antonio, TX 78249, USA;
| | | |
Collapse
|
11
|
Wang J, Ji Y, Ai C, Chen JR, Gan D, Zhang J, Mo JQ, Guan MX. Optimized allotopic expression of mitochondrial ND6 transgene restored complex I and apoptosis deficiencies caused by LHON-linked ND6 14484T > C mutation. J Biomed Sci 2023; 30:63. [PMID: 37537557 PMCID: PMC10399063 DOI: 10.1186/s12929-023-00951-1] [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: 03/09/2023] [Accepted: 07/11/2023] [Indexed: 08/05/2023] Open
Abstract
BACKGROUND Leber's hereditary optic neuropathy (LHON) is a maternally inherited eye disease due to mutations in mitochondrial DNA. However, there is no effective treatment for this disease. LHON-linked ND6 14484T > C (p.M64V) mutation caused complex I deficiency, diminished ATP production, increased production of reactive oxygen species (ROS), elevated apoptosis, and impaired mitophagy. Here, we investigated if the allotopic expression of human mitochondrial ND6 transgene corrected the mitochondrial dysfunctions due to LHON-associated m.14484T > C mutation. METHODS Nucleus-versions of ND6 was generated by changing 6 non-universal codons with universal codons and added to mitochondrial targeting sequence of COX8. Stable transfectants were generated by transferring human ND6 cDNA expressed in a pCDH-puro vector into mutant cybrids carrying the m.14484T > C mutation and control cybrids. The effect of allotopic expression of ND6 on oxidative phosphorylation (OXPHOS) was evaluated using Blue Native gel electrophoresis and extracellular flux analyzer. Assessment of ROS production in cell lines was performed by flow cytometry with MitoSOX Red reagent. Analyses for apoptosis and mitophagy were undertaken via flow cytometry, TUNEL and immunofluorescence assays. RESULTS The transfer of human ND6 into the cybrids carrying the m.14484T > C mutation raised the levels of ND6, ND1 and ND4L but did not change the levels of other mitochondrial proteins. The overexpression of ND6 led to 20~23% increases in the assembly and activity of complex I, and ~ 53% and ~ 33% increases in the levels of mitochondrial ATP and ΔΨm in the mutant cybrids bearing m.14484T > C mutation. Furthermore, mutant cybrids with overexpression of ND6 exhibited marked reductions in the levels of mitochondrial ROS. Strikingly, ND6 overexpression markedly inhibited the apoptosis process and restored impaired mitophagy in the cells carrying m.14484T > C mutation. However, overexpression of ND6 did not affect the ND6 level and mitochondrial functions in the wild-type cybrids, indicating that this ND6 level appeared to be the maximum threshold level to maintain the normal cell function. CONCLUSION We demonstrated that allotopic expression of nucleus-versions of ND6 restored complex I, apoptosis and mitophagy deficiencies caused by the m.14484T > C mutation. The restoration of m.14484T > C mutation-induced mitochondrial dysfunctions by overexpression of ND6 is a step toward therapeutic interventions for LHON and mitochondrial diseases.
Collapse
Affiliation(s)
- Jing Wang
- Center for Mitochondrial Biomedicine, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
- Division of Medical Genetics and Genomics, The Children's Hospital, Zhejiang University School of Medicine and National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China
- Institute of Genetics, Zhejiang University School of Medicine, 866 Yuhangtang Road, Hangzhou, Zhejiang, China
| | - Yanchun Ji
- Division of Medical Genetics and Genomics, The Children's Hospital, Zhejiang University School of Medicine and National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China
- Institute of Genetics, Zhejiang University School of Medicine, 866 Yuhangtang Road, Hangzhou, Zhejiang, China
| | - Cheng Ai
- Institute of Genetics, Zhejiang University School of Medicine, 866 Yuhangtang Road, Hangzhou, Zhejiang, China
| | - Jia-Rong Chen
- Center for Mitochondrial Biomedicine, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
- Division of Medical Genetics and Genomics, The Children's Hospital, Zhejiang University School of Medicine and National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China
- Institute of Genetics, Zhejiang University School of Medicine, 866 Yuhangtang Road, Hangzhou, Zhejiang, China
| | - Dingyi Gan
- Institute of Genetics, Zhejiang University School of Medicine, 866 Yuhangtang Road, Hangzhou, Zhejiang, China
| | - Juanjuan Zhang
- Institute of Genetics, Zhejiang University School of Medicine, 866 Yuhangtang Road, Hangzhou, Zhejiang, China
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jun Q Mo
- Department of Pathology, Rady Children's Hospital, University of California at San Diego School of Medicine, San Diego, California, USA
| | - Min-Xin Guan
- Center for Mitochondrial Biomedicine, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
- Division of Medical Genetics and Genomics, The Children's Hospital, Zhejiang University School of Medicine and National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China.
- Institute of Genetics, Zhejiang University School of Medicine, 866 Yuhangtang Road, Hangzhou, Zhejiang, China.
- Zhejiang Provincial Key Laboratory of Genetic and Developmental Disorders, Hangzhou, Zhejiang, China.
- Key Lab of Reproductive Genetics, Ministry of Education of PRC, Zhejiang University, Hangzhou, Zhejiang, China.
| |
Collapse
|
12
|
Sato G, Kuroda K. Overcoming the Limitations of CRISPR-Cas9 Systems in Saccharomyces cerevisiae: Off-Target Effects, Epigenome, and Mitochondrial Editing. Microorganisms 2023; 11:microorganisms11041040. [PMID: 37110464 PMCID: PMC10145089 DOI: 10.3390/microorganisms11041040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 04/12/2023] [Accepted: 04/13/2023] [Indexed: 04/29/2023] Open
Abstract
Modification of the genome of the yeast Saccharomyces cerevisiae has great potential for application in biological research and biotechnological advancements, and the CRISPR-Cas9 system has been increasingly employed for these purposes. The CRISPR-Cas9 system enables the precise and simultaneous modification of any genomic region of the yeast to a desired sequence by altering only a 20-nucleotide sequence within the guide RNA expression constructs. However, the conventional CRISPR-Cas9 system has several limitations. In this review, we describe the methods that were developed to overcome these limitations using yeast cells. We focus on three types of developments: reducing the frequency of unintended editing to both non-target and target sequences in the genome, inducing desired changes in the epigenetic state of the target region, and challenging the expansion of the CRISPR-Cas9 system to edit genomes within intracellular organelles such as mitochondria. These developments using yeast cells to overcome the limitations of the CRISPR-Cas9 system are a key factor driving the advancement of the field of genome editing.
Collapse
Affiliation(s)
- Genki Sato
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Kouichi Kuroda
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Department of Molecular Chemistry and Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan
| |
Collapse
|
13
|
Kar B, Castillo SR, Sabharwal A, Clark KJ, Ekker SC. Mitochondrial Base Editing: Recent Advances towards Therapeutic Opportunities. Int J Mol Sci 2023; 24:ijms24065798. [PMID: 36982871 PMCID: PMC10056815 DOI: 10.3390/ijms24065798] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 03/06/2023] [Accepted: 03/08/2023] [Indexed: 03/30/2023] Open
Abstract
Mitochondria are critical organelles that form networks within our cells, generate energy dynamically, contribute to diverse cell and organ function, and produce a variety of critical signaling molecules, such as cortisol. This intracellular microbiome can differ between cells, tissues, and organs. Mitochondria can change with disease, age, and in response to the environment. Single nucleotide variants in the circular genomes of human mitochondrial DNA are associated with many different life-threatening diseases. Mitochondrial DNA base editing tools have established novel disease models and represent a new possibility toward personalized gene therapies for the treatment of mtDNA-based disorders.
Collapse
Affiliation(s)
- Bibekananda Kar
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | - Santiago R Castillo
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
- Mayo Clinic Graduate School of Biomedical Sciences, Virology and Gene Therapy Track, Mayo Clinic, Rochester, MN 55905, USA
| | - Ankit Sabharwal
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | - Karl J Clark
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| | - Stephen C Ekker
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA
| |
Collapse
|