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Cunningham CJ, Choi RB, Bullock WA, Robling AG. Perspective: The current state of Cre driver mouse lines in skeletal research: Challenges and opportunities. Bone 2023; 170:116719. [PMID: 36868507 PMCID: PMC10087282 DOI: 10.1016/j.bone.2023.116719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 02/15/2023] [Accepted: 02/19/2023] [Indexed: 03/04/2023]
Abstract
The Cre/Lox system has revolutionized the ability of biomedical researchers to ask very specific questions about the function of individual genes in specific cell types at specific times during development and/or disease progression in a variety of animal models. This is true in the skeletal biology field, and numerous Cre driver lines have been created to foster conditional gene manipulation in specific subpopulations of bone cells. However, as our ability to scrutinize these models increases, an increasing number of issues have been identified with most driver lines. All existing skeletal Cre mouse models exhibit problems in one or more of the following three areas: (1) cell type specificity-avoiding Cre expression in unintended cell types; (2) Cre inducibility-improving the dynamic range for Cre in inducible models (negligible Cre activity before induction and high Cre activity after induction); and (3) Cre toxicity-reducing the unwanted biological effects of Cre (beyond loxP recombination) on cellular processes and tissue health. These issues are hampering progress in understanding the biology of skeletal disease and aging, and consequently, identification of reliable therapeutic opportunities. Skeletal Cre models have not advanced technologically in decades despite the availability of improved tools, including multi-promoter-driven expression of permissive or fragmented recombinases, new dimerization systems, and alternative forms of recombinases and DNA sequence targets. We review the current state of skeletal Cre driver lines, and highlight some of the successes, failures, and opportunities to improve fidelity in the skeleton, based on successes pioneered in other areas of biomedical science.
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Affiliation(s)
- Connor J Cunningham
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Roy B Choi
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, IN, USA
| | | | - Alexander G Robling
- Department of Anatomy, Cell Biology & Physiology, Indiana University School of Medicine, Indianapolis, IN, USA; Richard L. Roudebush Veterans Affairs Medical Center, Indianapolis, IN, USA; Department of Biomedical Engineering, Indiana University-Purdue University at Indianapolis, Indianapolis, IN, USA; Indiana Center for Musculoskeletal Health, Indianapolis, IN, USA.
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Hong J, Jeong Y, Heo WD. The Neurotrophic Receptor Tyrosine Kinase in MEC-mPFC Neurons Contributes to Remote Memory Consolidation. J Neurosci 2022; 42:6605-6619. [PMID: 35863892 PMCID: PMC9410758 DOI: 10.1523/jneurosci.2433-21.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 06/08/2022] [Accepted: 07/06/2022] [Indexed: 11/21/2022] Open
Abstract
The PFC is thought to be the region where remote memory is recalled. However, the neurotrophic receptors that underlie the remote memory remain largely unknown. Here, we benefited from auto-assembly split Cre to accomplish the neural projection-specific recombinase activity without spontaneous leakage. Deletion of tropomyosin receptor kinase B (TrkB) in neurons projecting from the medial entorhinal cortex to the mPFC displayed reduced remote memory recall from the male mice, but the recent recall was intact. We found that the TrkB deletion attenuates the participation of mPFC cells in the remote fear memory recall. The disruption of remote recall was attributed to reduced reactivation of cells in the mPFC. Notably, TrkB deletion seriously inhibited experience-dependent maturation of oligodendroglia in the PFC, resulting in defects in remote recall that were rescued by clemastine administration. Together, our data suggest that TrkB in intercortical circuits functions in remote memory consolidation.SIGNIFICANCE STATEMENT Retrieving the past experiences or events is essential for the ones to lead life. The investigations performed in the rodent model have disclosed that the systems consolidation of memory accompanying changes of cortical circuits and transcriptome is required for maintaining the memory for a long time. In this study, the split Cre with TrkBflox/flox mice were subjected to discover that TrkB in the neurons plays a role in remote memory consolidation. We evaluated the contextual fear memory and labeled cells, which revealed deletion of TrkB interrupts newborn oligodendrocyte and reactivation of cells in mPFC at remote recall. Our data provide the implication that remote memory is relevant to neurotrophic receptor signaling as well as its influence on non-neuronal cells.
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Affiliation(s)
- Jongryul Hong
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Yeonji Jeong
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
| | - Won Do Heo
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Republic of Korea
- Korea Advanced Institute of Science and Technology Institute for the BioCentury, Daejeon, 34141, Republic of Korea
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Wei X, Zhang J, Cui J, Xu W, Zhou X, Ma J. A Split-Cre system designed to detect simultaneous expression of two genes based on SpyTag/SpyCatcher conjugation and Split-GFP dimerization. J Biol Chem 2021; 297:101119. [PMID: 34450162 PMCID: PMC8455372 DOI: 10.1016/j.jbc.2021.101119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 08/14/2021] [Accepted: 08/23/2021] [Indexed: 12/04/2022] Open
Abstract
The Split-Cre system is a powerful tool for genetic manipulation and can be used to spatiotemporally control gene expression in vivo. However, the low activity of the reconstituted NCre/CCre recombinase in the Split-Cre system limits its application as an indicator of the simultaneous expression of a pair of genes of interest. Here, we describe two approaches for improving the activity of the Split-Cre system after Cre reconstitution based on self-associating split GFP (Split-GFP) and SpyTag/SpyCatcher conjugation. First, we created the Split-GFP-Cre system by constructing fusion proteins of NCre and CCre with the N-terminal and C-terminal subunits of GFP, respectively. Reconstitution of Cre by GFP-mediated dimerization of the two fusion proteins resulted in recombinase activity approaching that of full-length Cre in living cells. Second, to further increase recombinase activity at low levels of Split-Cre expression, the Split-Spy-GCre system was established by incorporating the sequences for SpyTag and SpyCatcher into the components of the Split-GFP-Cre system. As anticipated, covalent conjugation of the SpyTag and SpyCatcher segments improved Split-GFP dimerization to further increase Cre recombinase activity in living cells. The increased efficiency and robustness of this dual-split system (Split-Cre and Split-GFP) minimize the problems of incomplete double gene-specific KO or low labeling efficiency due to poor NCre/CCre recombinase activity. Thus, this Split-Spy-GCre system allows more precise gene manipulation of cell subpopulations, which will provide advanced analysis of genes and cell functions in complex tissue such as the immune system.
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Affiliation(s)
- Xundong Wei
- Center of Biotherapy, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China; Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| | - Jianhua Zhang
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China; CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing, China
| | - Jian Cui
- Department of General Surgery, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China
| | - Wei Xu
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China; CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing, China
| | - Xuyu Zhou
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China; CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing, China.
| | - Jie Ma
- Center of Biotherapy, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China; Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China.
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Yang C, Ge J, Fu X, Luo K, Xu C. Dual Reproductive Cell-Specific Promoter-Mediated Split-Cre/LoxP System Suitable for Exogenous Gene Deletion in Hybrid Progeny of Transgenic Arabidopsis. Int J Mol Sci 2021; 22:5080. [PMID: 34064885 PMCID: PMC8151399 DOI: 10.3390/ijms22105080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/07/2021] [Accepted: 05/10/2021] [Indexed: 01/02/2023] Open
Abstract
Genetically modified (GM) crops possess some superior characteristics, such as high yield and insect resistance, but their biosafety has aroused broad public concern. Some genetic engineering technologies have recently been proposed to remove exogenous genes from GM crops. Few approaches have been applied to maintain advantageous traits, but excising exogenous genes in seeds or fruits from these hybrid crops has led to the generation of harvested food without exogenous genes. In a previous study, split-Cre mediated by split intein could recombine its structure and restore recombination activity in hybrid plants. In the current study, the recombination efficiency of split-Cre under the control of ovule-specific or pollen-specific promoters was validated by hybridization of transgenic Arabidopsis containing the improved expression vectors. In these vectors, all exogenous genes were flanked by two loxP sites, including promoters, resistance genes, reporter genes, and split-Cre genes linked to the reporter genes via LP4/2A. A gene deletion system was designed in which NCre was driven by proDD45, and CCre was driven by proACA9 and proDLL. Transgenic lines containing NCre were used as paternal lines to hybridize with transgenic lines containing CCre. Because this hybridization method results in no co-expression of the NCre and CCre genes controlled by reproduction-specific promoters in the F1 progeny, the desirable characteristics could be retained. After self-crossing in F1 progeny, the expression level and protein activity of reporter genes were detected, and confirmed that recombination of split-Cre had occurred and the exogenous genes were partially deleted. The gene deletion efficiency represented by the quantitative measurements of GUS enzyme activity was over 59%, with the highest efficiency of 73% among variable hybrid combinations. Thus, in the present study a novel dual reproductive cell-specific promoter-mediated gene deletion system was developed that has the potential to take advantage of the merits of GM crops while alleviating biosafety concerns.
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Affiliation(s)
| | | | | | - Keming Luo
- Chongqing Key Laboratory of Plant Resource Conservation and Germplasm Innovation, Key Laboratory of Eco-Environments of Three Gorges Reservoir Region, Ministry of Education, School of Life Sciences, Southwest University, Chongqing 400715, China; (C.Y.); (J.G.); (X.F.)
| | - Changzheng Xu
- Chongqing Key Laboratory of Plant Resource Conservation and Germplasm Innovation, Key Laboratory of Eco-Environments of Three Gorges Reservoir Region, Ministry of Education, School of Life Sciences, Southwest University, Chongqing 400715, China; (C.Y.); (J.G.); (X.F.)
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Rajaee M, Ow DW. A new location to split Cre recombinase for protein fragment complementation. PLANT BIOTECHNOLOGY JOURNAL 2017; 15:1420-1428. [PMID: 28317293 PMCID: PMC5633763 DOI: 10.1111/pbi.12726] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 03/13/2017] [Accepted: 03/13/2017] [Indexed: 06/06/2023]
Abstract
We have previously described a recombinase-mediated gene stacking system in which the Cre recombinase is used to remove lox-site flanked DNA no longer needed after each round of Bxb1 integrase-mediated site-specific integration. The Cre recombinase can be conveniently introduced by hybridization with a cre-expressing plant. However, maintaining an efficient cre-expressing line over many generations can be a problem, as high production of this DNA-binding protein might interfere with normal chromosome activities. To counter this selection against high Cre activity, we considered a split-cre approach, in which Cre activity is reconstituted after separate parts of Cre are brought into the same genome by hybridization. To insure that the recombinase-mediated gene stacking system retains its freedom to operate, we tested for new locations to split Cre into complementing fragments. In this study, we describe testing four new locations for splitting the Cre recombinase for protein fragment complementation and show that the two fragments of Cre split between Lys244 and Asn245 can reconstitute activity that is comparable to that of wild-type Cre.
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Affiliation(s)
- Maryam Rajaee
- Plant Gene Engineering CenterSouth China Botanical GardenChinese Academy of SciencesGuangzhouChina
- University of Chinese Academy of SciencesBeijingChina
| | - David W. Ow
- Plant Gene Engineering CenterSouth China Botanical GardenChinese Academy of SciencesGuangzhouChina
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Ge J, Wang L, Yang C, Ran L, Wen M, Fu X, Fan D, Luo K. Intein-mediated Cre protein assembly for transgene excision in hybrid progeny of transgenic Arabidopsis. PLANT CELL REPORTS 2016; 35:2045-2053. [PMID: 27324752 DOI: 10.1007/s00299-016-2015-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 06/07/2016] [Indexed: 06/06/2023]
Abstract
An approach for restoring recombination activity of complementation split-Cre was developed to excise the transgene in hybrid progeny of GM crops. Growing concerns about the biosafety of genetically modified (GM) crops has currently become a limited factor affecting the public acceptance. Several approaches have been developed to generate selectable-marker-gene-free GM crops. However, no strategy was reported to be broadly applicable to hybrid crops. Previous studies have demonstrated that complementation split-Cre recombinase restored recombination activity in transgenic plants. In this study, we found that split-Cre mediated by split-intein Synechocystis sp. DnaE had high recombination efficiency when Cre recombinase was split at Asp232/Asp233 (866 bp). Furthermore, we constructed two plant expression vectors, pCA-NCre-In and pCA-Ic-CCre, containing NCre866-In and Ic-CCre866 fragments, respectively. After transformation, parent lines of transgenic Arabidopsis with one single copy were generated and used for hybridization. The results of GUS staining demonstrated that the recombination activity of split-Cre could be reassembled in these hybrid progeny of transgenic plants through hybridization and the foreign genes flanked by two loxP sites were efficiently excised. Our strategy may provide an effective approach for generating the next generation of GM hybrid crops without biosafety concerns.
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Affiliation(s)
- Jia Ge
- Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Lijun Wang
- Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Chen Yang
- Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Lingyu Ran
- Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Mengling Wen
- Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Xianan Fu
- Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Di Fan
- Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing, 400715, China
| | - Keming Luo
- Institute of Resources Botany, School of Life Sciences, Southwest University, Chongqing, 400715, China.
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