1
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Liu Z, Li M, Sun Y, Wang W, Wang Z, Presicce GA, An L, Du F. Epigenetic dynamics of H4K20me3 modification during oocyte maturation and early reprogramming of somatic cell nuclear transfer goat embryos. Am J Transl Res 2022; 14:5941-5951. [PMID: 36105059 PMCID: PMC9452338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 08/22/2022] [Indexed: 06/15/2023]
Abstract
OBJECTIVE We examined the epigenetic dynamics of histone H4K20 trimethylation (H4K20me3), a repressive signature in heterochromatin, during goat oocyte meiosis and the reprogramming of somatic cell nuclear transfer (NT) embryos through the first three cell divisions. METHODS Following NT, oocytes were treated with parthenogenetic activation (PA), by 5 µM calcium ionophore A23187 for 5 min followed by incubation in 2.0 mM 6-dimethylaminopurine with 5 µg/mL cycloheximide for 4 h. NT embryos up to 8-celled stage were incubated with H4K20me3 antibody. RESULTS Immunofluorescence microscopy revealed the existence of a persistent H4K20me3 signature during oocyte maturation from germinal vesicle phase to metaphase I, anaphase I, telophase I, and metaphase II, with a gradual reduction in staining intensity. NT embryos at the 2-, 4- and 8-celled stage showed lower H4K20me3 intensity than PA and IVF embryos (P < 0.05). CONCLUSION These results indicate that NT embryos exhibit insufficient H4K20me3 modification compared with IVF and PA embryos during early reprogramming, suggesting the existence of a resistant memory of differentiated cell nuclear architecture. These findings help unravel the epigenetic mechanism of histone H4K20me3 in goat nuclear transfer reprogramming.
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Affiliation(s)
- Zhihui Liu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, Jiangsu, PR China
| | - Mingyang Li
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, Jiangsu, PR China
| | - Yu Sun
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, Jiangsu, PR China
| | - Weiguo Wang
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, Jiangsu, PR China
| | - Zhisong Wang
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, Jiangsu, PR China
| | | | - Liyou An
- Xinjiang Key Laboratory of Biological Resources and Genetic Engineering, College of Life Science and Technology, Xinjiang UniversityUrumqi 830046, Xinjiang, PR China
| | - Fuliang Du
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, Jiangsu, PR China
- Renova Life Inc., College ParkMaryland 20742, USA
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2
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Cao W, Zhao J, Qu P, Liu E. Current Progress and Prospects in Rabbit Cloning. Cell Reprogram 2022; 24:63-70. [PMID: 35167365 DOI: 10.1089/cell.2021.0090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Somatic cell nuclear transfer (SCNT) shows great value in the generation of transgenic animals, protection of endangered animals, and stem cell therapy. The combination of SCNT and gene editing has produced a variety of genetically modified animals for life science and medical research. Rabbits have unique advantages as transgenic bioreactors and human disease models; however, the low SCNT efficiency severely impedes the application of this technology. The difficulty in SCNT may be attributable to the abnormal reprogramming of somatic cells in rabbits. This review focuses on the abnormal reprogramming of cloned mammalian embryos and evaluates the progress and prospects of rabbit somatic cell cloning.
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Affiliation(s)
- Wenbin Cao
- Laboratory Animal Center, Xi'an Jiaotong University Health Science Center, Xi'an, China
| | - Jinpeng Zhao
- Laboratory Animal Center, Xi'an Jiaotong University Health Science Center, Xi'an, China
| | - Pengxiang Qu
- Laboratory Animal Center, Xi'an Jiaotong University Health Science Center, Xi'an, China
| | - Enqi Liu
- Laboratory Animal Center, Xi'an Jiaotong University Health Science Center, Xi'an, China
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3
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Song J, Zhang J, Xu J, Garcia-Barrio M, Chen YE, Yang D. Genome engineering technologies in rabbits. J Biomed Res 2021; 35:135-147. [PMID: 32934190 PMCID: PMC8038526 DOI: 10.7555/jbr.34.20190133] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The rabbit has been recognized as a valuable model in various biomedical and biological research fields because of its intermediate size and phylogenetic proximity to primates. However, the technology for precise genome manipulations in rabbit has been stalled for decades, severely limiting its applications in biomedical research. Novel genome editing technologies, especially CRISPR/Cas9, have remarkably enhanced precise genome manipulation in rabbits, and shown their superiority and promise for generating rabbit models of human genetic diseases. In this review, we summarize the brief history of transgenic rabbit technology and the development of novel genome editing technologies in rabbits.
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Affiliation(s)
- Jun Song
- Center for Advanced Models for Translational Sciences and Therapeutics, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | - Jifeng Zhang
- Center for Advanced Models for Translational Sciences and Therapeutics, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | - Jie Xu
- Center for Advanced Models for Translational Sciences and Therapeutics, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | - Minerva Garcia-Barrio
- Center for Advanced Models for Translational Sciences and Therapeutics, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | - Y Eugene Chen
- Center for Advanced Models for Translational Sciences and Therapeutics, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | - Dongshan Yang
- Center for Advanced Models for Translational Sciences and Therapeutics, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
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4
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Liu J, An L, Wang J, Liu Z, Dai Y, Liu Y, Yang L, Du F. Dynamic patterns of H3K4me3, H3K27me3, and Nanog during rabbit embryo development. Am J Transl Res 2019; 11:430-441. [PMID: 30787999 PMCID: PMC6357316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 12/14/2018] [Indexed: 06/09/2023]
Abstract
Epigenetic modification and expression of key pluripotent factors are critical for development, cell fate determination, and differentiation in early embryos. In this study, we systematically examined the dynamic patterns of histone modifications (H3K4me3 and H3K27me3) and Nanog expression during the development of preimplantation rabbit embryos. Rabbit oocytes, 1-, 2-, 4-, 8-, and 16-cell embryos, morulae, and blastocysts were collected at specific time points following superovulation and assessed for nuclear H3K4me3, H3K27me3, and Nanog expression by immunofluorescence microscopy. The frequency of H3K4me3-positive nuclear staining was highest in oocytes through 4-cell embryos (100%), decreased in 8-cell (97.2%) and 16-cell (94.4%) embryos (P > 0.05), declined dramatically in morulae (86.7%) (1- through 8-cell embryos vs morulae, P < 0.05), and was the lowest in blastocysts (76.2%) (P < 0.05). Nuclear staining of H3K27me3 was negative in oocytes and embryos through the 16-cell stage but was positive in 25.9% of morulae and 34.2% of blastocyst (P < 0.05). Similarly, rabbit oocytes and embryos through the 16-cell stage did not express Nanog, but Nanog was expressed in 24.9% of morulae and 36.5% of blastocysts (P < 0.05). The observed decrease in H3K4me3 and increase in H3K27me3 as development progressed in preimplantation rabbit embryos, together with late Nanog expression, indicates a correlation of these factors with early embryonic cell fate determination and differentiation. Our study provides a specific and dynamic profile of histone modifications and gene expression that will be important for the derivation of rabbit embryonic stem cells and improving rabbit cloning by somatic cell nuclear transfer.
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Affiliation(s)
- Jiao Liu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, PR China
| | - Liyou An
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, PR China
| | - Jiqiang Wang
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, PR China
| | - Zhihui Liu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, PR China
| | - Yujian Dai
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, PR China
| | - Yanhong Liu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, PR China
| | - Lan Yang
- Lannuo Biotechnologies Wuxi Inc.Wuxi 214000, PR China
| | - Fuliang Du
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal UniversityNanjing 210046, PR China
- Lannuo Biotechnologies Wuxi Inc.Wuxi 214000, PR China
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5
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Abstract
Due to the lack of germline transmitting pluripotent stem cells (PSCs) cell lines and the extreme difficulty of somatic cell nuclear transfer (SCNT) in rabbit, the gene targeting technology in rabbit was lagging far behind those in rodents and in farm animals. As a result, the development and application of genetically engineered rabbit model are much limited. With the advent of gene editing nucleases, including ZFN, TALEN, and CRISPR/Cas9, it is now possible to produce gene targeting (i.e., knockout, knockin) rabbits with high success rates. In this chapter, we describe a comprehensive, step-by-step protocol for rabbit genome editing based on gene editing nucleases with specific emphasis of CRISPR/Cas9.
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6
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Cordova A, King WA, Mastromonaco GF. Choosing a culture medium for SCNT and iSCNT reconstructed embryos: from domestic to wildlife species. JOURNAL OF ANIMAL SCIENCE AND TECHNOLOGY 2017; 59:24. [PMID: 29152322 PMCID: PMC5680814 DOI: 10.1186/s40781-017-0149-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 10/23/2017] [Indexed: 12/16/2022]
Abstract
Over the past decades, in vitro culture media have been developed to successfully support IVF embryo growth in a variety of species. Advanced reproductive technologies, such as somatic cell nuclear transfer (SCNT), challenge us with a new type of embryo, with special nutritional requirements and altered physiology under in vitro conditions. Numerous studies have successfully reconstructed cloned embryos of domestic animals for biomedical research and livestock production. However, studies evaluating suitable culture conditions for SCNT embryos in wildlife species are scarce (for both intra- and interspecies SCNT). Most of the existing studies derive from previous IVF work done in conventional domestic species. Extrapolation to non-domestic species presents significant challenges since we lack information on reproductive processes and embryo development in most wildlife species. Given the challenges in adapting culture media and conditions from IVF to SCNT embryos, developmental competence of SCNT embryos remains low. This review summarizes research efforts to tailor culture media to SCNT embryos and explore the different outcomes in diverse species. It will also consider how these culture media protocols have been extrapolated to wildlife species, most particularly using SCNT as a cutting-edge technical resource to assist in the preservation of endangered species.
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Affiliation(s)
- A Cordova
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario Canada.,Reproductive Physiology, Toronto Zoo, Scarborough, Ontario Canada
| | - W A King
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario Canada
| | - G F Mastromonaco
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario Canada.,Reproductive Physiology, Toronto Zoo, Scarborough, Ontario Canada
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7
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Xiao J, Li Q, Qu P, Zhang Z, Pan S, Wang Y, Zhang Y. Isolation of Bovine Skin-Derived Precursor Cells and Their Developmental Potential After Nuclear Transfer. Cell Reprogram 2016; 18:411-418. [PMID: 27906583 DOI: 10.1089/cell.2016.0021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Nuclei from less differentiated stem cells yield high cloning efficiency. However, pluripotent stem cells are rather difficult to obtain from bovines. Skin-derived precursor (SKPs) cells exhibit a certain degree of pluripotency, which has been shown to enhance the efficiency of nuclear transfer (NT) in pigs. In this study, bovine SKPs were isolated and characterized. Results showed that bovine SKPs expressed nestin, fibronectin, vimentin, pluripotency-related genes, and characteristic neural crest markers, such as NGFR, PAX3, SOX9, SNAI2, and OCT4. Bovine SKPs and fibroblasts were used as NT donor cells to examine and compare the preimplantation developmental potential of reconstructed embryos after somatic cell nuclear transfer (SCNT). Bovine SKP-cloned embryos displayed higher developmental competence in terms of blastocyst formation rate and total cell number in blastocysts compared with the bovine embryonic fibroblast-cloned embryos. This study revealed that bovine SKPs may be considered excellent candidate nuclear donors for SCNT and may provide a promising platform for transgenic cattle generation.
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Affiliation(s)
- Jiajia Xiao
- 1 College of Veterinary Medicine, Northwest A&F University , Yangling, Shaanxi, 712100 China .,2 Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University , Yangling, Shaanxi, 712100 China
| | - Qiaoqiao Li
- 1 College of Veterinary Medicine, Northwest A&F University , Yangling, Shaanxi, 712100 China .,2 Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University , Yangling, Shaanxi, 712100 China
| | - Pengxiang Qu
- 1 College of Veterinary Medicine, Northwest A&F University , Yangling, Shaanxi, 712100 China .,2 Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University , Yangling, Shaanxi, 712100 China
| | - Zihan Zhang
- 1 College of Veterinary Medicine, Northwest A&F University , Yangling, Shaanxi, 712100 China .,2 Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University , Yangling, Shaanxi, 712100 China
| | - Shaohui Pan
- 1 College of Veterinary Medicine, Northwest A&F University , Yangling, Shaanxi, 712100 China .,2 Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University , Yangling, Shaanxi, 712100 China
| | - Yongsheng Wang
- 1 College of Veterinary Medicine, Northwest A&F University , Yangling, Shaanxi, 712100 China .,2 Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University , Yangling, Shaanxi, 712100 China
| | - Yong Zhang
- 1 College of Veterinary Medicine, Northwest A&F University , Yangling, Shaanxi, 712100 China .,2 Key Laboratory of Animal Biotechnology, Ministry of Agriculture, Northwest A&F University , Yangling, Shaanxi, 712100 China
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8
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Intawicha P, Siriboon C, Chen CH, Chiu YT, Lin TA, Kere M, Lo NW, Lee KH, Chang LY, Chiang HI, Ju JC. Derivation and characterization of putative embryonic stem cells from cloned rabbit embryos. Theriogenology 2016; 86:1799-810. [DOI: 10.1016/j.theriogenology.2016.05.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Revised: 05/24/2016] [Accepted: 05/27/2016] [Indexed: 12/19/2022]
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9
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Song S, Ge X, Cheng Y, Lu R, Zhang T, Yu B, Ji X, Qi Z, Rong Y, Yuan Y, Cheng Y. High-level expression of a novel recombinant human plasminogen activator (rhPA) in the milk of transgenic rabbits and its thrombolytic bioactivity in vitro. Mol Biol Rep 2016; 43:775-83. [PMID: 27230577 DOI: 10.1007/s11033-016-4020-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Accepted: 05/21/2016] [Indexed: 12/19/2022]
Abstract
The human tissue-type plasminogen activator (tPA) is a key kinase of fibrinolysis that plays an important role in dissolving fibrin clots to promote thrombolysis. The recombinant human plasminogen activator (rhPA) has more thrombolytic advantages than the wild type tPA. To increase the half-life and thrombolytic activity of tPA, a mutant containing only the essential K2 fibrin-binding and P activating plasminogen domains of the wild type tPA was cloned. This fragment was then inserted into goat β-casein regulatory sequences. Then, a mammary gland-specific expression vector, PCL25/rhPA, was constructed, and the transgenic rabbits were generated. In this study, 18 live transgenic founders (12♀, 6♂) were generated using pronuclear microinjection. Six transgenic rabbits were obtained, and the expression levels of rhPA in the milk had a range of 15.2-630 µg/ml. A fibrin agarose plate assay of rhPA showed that it had strong thrombolytic bioactivity in vitro, and the highest specific activity was >360 (360 times more than that of alteplase). The results indicated that the rhPA containing only the K2 and P domains is efficiently expressed with higher thrombolytic bioactivity in the milk of transgenic rabbits. Our study also demonstrated a new method for the large-scale production of clinically relevant recombinant pharmaceutical proteins in the mammary glands of transgenic rabbits.
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Affiliation(s)
- Shaozheng Song
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, People's Republic of China
| | - Xin Ge
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China
| | - Yaobin Cheng
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China
| | - Rui Lu
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China
| | - Ting Zhang
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China
| | - Baoli Yu
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China
| | - Xueqiao Ji
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China
| | - Zhengqiang Qi
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China
| | - Yao Rong
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China
| | - Yuguo Yuan
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, People's Republic of China
| | - Yong Cheng
- Engineering Research Centre for Transgenic Animal Pharmaceutics in Jiangsu Province, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, Jiangsu, People's Republic of China. .,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, People's Republic of China.
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10
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Liu Y, Wang H, Lu J, Miao Y, Cao X, Zhang L, Wu X, Wu F, Ding B, Wang R, Luo M, Li W, Tan J. Rex Rabbit Somatic Cell Nuclear Transfer with In Vitro-Matured Oocytes. Cell Reprogram 2016; 18:187-94. [PMID: 27159389 DOI: 10.1089/cell.2015.0086] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Somatic cell nuclear transfer (SCNT) requires large numbers of matured oocytes. In vitro-matured (IVM) oocytes have been used in SCNT in many animals. We investigated the use of IVM oocytes in Rex rabbit SCNT using Rex rabbit ovaries obtained from a local abattoir. The meiotic ability of oocytes isolated from follicles of different diameters was studied. Rex rabbit SCNT was optimized for denucleation, activation, and donor cell synchronization. Rex rabbit oocytes grew to the largest diameter (110 μm) when the follicle diameter was 1.0 mm. Oocytes isolated from <0.5-mm follicles lacked the ability to resume meiosis. More than 90% of these oocytes remained in the germinal vesicle (GV) stage after in vitro culture (IVC) for 18 h. Oocytes isolated from >0.7-mm follicles acquired maturation ability. More than 90% of these oocytes matured after IVC for 18 h. The developmental potential of oocytes isolated from >1-mm follicles was greater than that of oocytes isolated from 0.7- to 1.0-mm follicles. The highest activation rates for IVM Rex rabbit oocytes were seen after treatment with 2.5 μM ionomycin for 5 min followed by 2 mM 6-dimethylaminopurine (6-DMAP) and 5 μg/mL cycloheximide (CHX) for 1 h. Ionomycin induced the chromatin of IVM oocytes to protrude from the oocyte surface, promoting denucleation. Fetal fibroblast cells (FFCs) and cumulus cells (CCs) were more suitable for Rex rabbit SCNT than skin fibroblast cells (SFCs) (blastocyst rate was 35.6 ± 2.2% and 38.0 ± 6.0% vs. 19.7 ± 3.1%). The best fusion condition was a 2DC interval for 1 sec, 1.6 kV/cm voltages, and 40 μsec duration in 0.28 M mannitol. In conclusion, the in vitro maturation of Rex rabbit oocytes and SCNT procedures were studied systematically and optimized in this study.
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Affiliation(s)
- Yong Liu
- 1 Key Laboratory of Embryo Development and Reproductive Regulation of Anhui Province, College of Biological and Food Engineering, Fuyang Teachers College , Fuyang City, Anhui Province 236037, China
| | - Huili Wang
- 2 Laboratory for Animal Reproduction and Embryology, College of Animal Science and Veterinary Medicine, Shandong Agricultural University , Tai'an City, Shandong Province 271018, China
| | - Jinhua Lu
- 2 Laboratory for Animal Reproduction and Embryology, College of Animal Science and Veterinary Medicine, Shandong Agricultural University , Tai'an City, Shandong Province 271018, China
| | - Yiliang Miao
- 2 Laboratory for Animal Reproduction and Embryology, College of Animal Science and Veterinary Medicine, Shandong Agricultural University , Tai'an City, Shandong Province 271018, China
| | - Xinyan Cao
- 2 Laboratory for Animal Reproduction and Embryology, College of Animal Science and Veterinary Medicine, Shandong Agricultural University , Tai'an City, Shandong Province 271018, China
| | - Ling Zhang
- 1 Key Laboratory of Embryo Development and Reproductive Regulation of Anhui Province, College of Biological and Food Engineering, Fuyang Teachers College , Fuyang City, Anhui Province 236037, China
| | - Xiaoqing Wu
- 1 Key Laboratory of Embryo Development and Reproductive Regulation of Anhui Province, College of Biological and Food Engineering, Fuyang Teachers College , Fuyang City, Anhui Province 236037, China
| | - Fengrui Wu
- 1 Key Laboratory of Embryo Development and Reproductive Regulation of Anhui Province, College of Biological and Food Engineering, Fuyang Teachers College , Fuyang City, Anhui Province 236037, China
| | - Biao Ding
- 1 Key Laboratory of Embryo Development and Reproductive Regulation of Anhui Province, College of Biological and Food Engineering, Fuyang Teachers College , Fuyang City, Anhui Province 236037, China
| | - Rong Wang
- 1 Key Laboratory of Embryo Development and Reproductive Regulation of Anhui Province, College of Biological and Food Engineering, Fuyang Teachers College , Fuyang City, Anhui Province 236037, China
| | - Mingjiu Luo
- 2 Laboratory for Animal Reproduction and Embryology, College of Animal Science and Veterinary Medicine, Shandong Agricultural University , Tai'an City, Shandong Province 271018, China
| | - Wenyong Li
- 1 Key Laboratory of Embryo Development and Reproductive Regulation of Anhui Province, College of Biological and Food Engineering, Fuyang Teachers College , Fuyang City, Anhui Province 236037, China
| | - Jinghe Tan
- 2 Laboratory for Animal Reproduction and Embryology, College of Animal Science and Veterinary Medicine, Shandong Agricultural University , Tai'an City, Shandong Province 271018, China
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11
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Yelisetti UM, Komjeti S, Katari VC, Sisinthy S, Brahmasani SR. Interspecies nuclear transfer using fibroblasts from leopard, tiger, and lion ear piece collected postmortem as donor cells and rabbit oocytes as recipients. In Vitro Cell Dev Biol Anim 2016; 52:632-45. [DOI: 10.1007/s11626-016-0014-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Accepted: 02/25/2016] [Indexed: 12/14/2022]
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12
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Du F, Chen CH, Li Y, Hu Y, An LY, Yang L, Zhang J, Chen YE, Xu J. Derivation of Rabbit Embryonic Stem Cells from Vitrified-Thawed Embryos. Cell Reprogram 2015; 17:453-62. [PMID: 26579970 DOI: 10.1089/cell.2015.0044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The rabbit is a useful animal model for regenerative medicine. We previously developed pluripotent rabbit embryonic stem cell (rbESC) lines using fresh embryos. We also successfully cryopreserved rabbit embryos by vitrification. In the present work, we combined these two technologies to derive rbESCs using vitrified-thawed (V/T) embryos. We demonstrate that V/T blastocysts (BLs) can be used to derive pluripotent rbESCs with efficiencies comparable to those using fresh BLs. These ESCs are undistinguishable from the ones derived from fresh embryos. We tested the developmental capacity of rbESCs derived from V/T embryos by BL injection experiments and produced chimeric kits. Our work adds cryopreservation to the toolbox of rabbit stem cell research and applications and will greatly expand the available research materials for regenerative medicine in a clinically relevant animal model.
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Affiliation(s)
- Fuliang Du
- 1 Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University , Nanjing 210046, China .,2 Renova Life, Inc. , College Park, Maryland 20742.,5 These authors contributed equally to this work
| | - Chien-Hong Chen
- 2 Renova Life, Inc. , College Park, Maryland 20742.,5 These authors contributed equally to this work
| | - Yi Li
- 1 Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University , Nanjing 210046, China
| | - Yeshu Hu
- 1 Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University , Nanjing 210046, China
| | - Li-You An
- 1 Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University , Nanjing 210046, China
| | - Lan Yang
- 3 Lannuo Biotechnologies Wuxi, Inc. , Wuxi, Jiangsu 214174, China
| | - Jifeng Zhang
- 4 Center for Advanced Models for Translational Sciences and Therapeutics, University of Michigan Medical Center , Ann Arbor, MI, 48109
| | - Y Eugene Chen
- 4 Center for Advanced Models for Translational Sciences and Therapeutics, University of Michigan Medical Center , Ann Arbor, MI, 48109
| | - Jie Xu
- 2 Renova Life, Inc. , College Park, Maryland 20742.,4 Center for Advanced Models for Translational Sciences and Therapeutics, University of Michigan Medical Center , Ann Arbor, MI, 48109
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13
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Choi YH, Velez IC, Macías-García B, Hinrichs K. Timing factors affecting blastocyst development in equine somatic cell nuclear transfer. Cell Reprogram 2015; 17:124-30. [PMID: 25826725 DOI: 10.1089/cell.2014.0093] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In nuclear transfer (NT), exposure of donor cell chromatin to the ooplast cytoplasm may aid reprogramming; however, the length of exposure feasible is limited by the developmental life span of the oocyte. We examined the effect of duration of nucleus-cytoplasmic exposure before activation and of in vitro maturation (IVM) in equine NT. In experiment 1, 24 h IVM and a delay of 2, 5, or 8 h between reconstruction and activation yielded 4%, 15%, and 11% blastocysts, respectively. In experiment 2, a 5-h activation delay yielded 17% and 22% blastocysts with two donor cell lines. In experiment 3, using a 5-h activation delay, the blastocyst rate was significantly higher using oocytes after 20 h IVM than after 24 h IVM; however, only 28% of oocytes were in metaphase II (MII) at 20 h. In experiment 4, oocytes were denuded of cumulus at 20 h, and those in metaphase I (MI) were returned to culture for 3 h (20+3H treatment); blastocyst rates were 30% and 27%, respectively (8-h and 5-h delay to activation, respectively). Four live foals resulted from the transfer of 17 blastocysts (24%) produced using MII oocytes and a 5- or 8-h activation delay. Use of equine oocytes immediately after reaching MII, combined with a longer delay from reconstruction to activation, increased developmental competence after equine NT.
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Affiliation(s)
- Young-Ho Choi
- Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University , College Station, Texas, 77843
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Niemann H, Lucas-Hahn A. Somatic cell nuclear transfer cloning: practical applications and current legislation. Reprod Domest Anim 2013; 47 Suppl 5:2-10. [PMID: 22913555 DOI: 10.1111/j.1439-0531.2012.02121.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Somatic cloning is emerging as a new biotechnology by which the opportunities arising from the advances in molecular genetics and genome analysis can be implemented in animal breeding. Significant improvements have been made in SCNT protocols in the past years which now allow to embarking on practical applications. The main areas of application of SCNT are: Reproductive cloning, therapeutic cloning and basic research. A great application potential of SCNT based cloning is the production of genetically modified (transgenic) animals. Somatic cell nuclear transfer based transgenic animal production has significant advances over the previously employed microinjection of foreign DNA into pronuclei of zygotes. This cell based transgenesis is compatible with gene targeting and allows both, the addition of a specific gene and the deletion of an endogenous gene. Efficient transgenic animal production provides numerous opportunities for agriculture and biomedicine. Regulatory agencies around the world have agreed that food derived from cloned animals and their offspring is safe and there is no scientific basis for questioning this. Commercial application of somatic cloning within the EU is via the Novel Food regulation EC No. 258/97. Somatic cloning raises novel questions regarding the ethical and moral status of animals and their welfare which has prompted a controversial discussion in Europe which has not yet been resolved.
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Affiliation(s)
- H Niemann
- Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Mariensee, Neustadt, Germany.
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Xue F, Ma Y, Chen YE, Zhang J, Lin TA, Chen CH, Lin WW, Roach M, Ju JC, Yang L, Du F, Xu J. Recombinant rabbit leukemia inhibitory factor and rabbit embryonic fibroblasts support the derivation and maintenance of rabbit embryonic stem cells. Cell Reprogram 2012; 14:364-76. [PMID: 22775411 DOI: 10.1089/cell.2012.0001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
The rabbit is a classical experimental animal species. A major limitation in using rabbits for biomedical research is the lack of germ-line-competent rabbit embryonic stem cells (rbESCs). We hypothesized that the use of homologous feeder cells and recombinant rabbit leukemia inhibitory factor (rbLIF) might improve the chance in deriving germ-line-competent rbES cells. In the present study, we established rabbit embryonic fibroblast (REF) feeder layers and synthesized recombinant rbLIF. We derived a total of seven putative rbESC lines, of which two lines (M5 and M23) were from culture Condition I using mouse embryonic fibroblasts (MEFs) as feeders supplemented with human LIF (hLIF) (MEF+hLIF). Another five lines (R4, R9, R15, R21, and R31) were derived from Condition II using REFs as feeder cells supplemented with rbLIF (REF+rbLIF). Similar derivation efficiency was observed between these two conditions (8.7% vs. 10.2%). In a separate experiment with 2×3 factorial design, we examined the effects of feeder cells (MEF vs. REF) and LIFs (mLIF, hLIF vs. rbLIF) on rbESC culture. Both Conditions I and II supported satisfactory rbESC culture, with similar or better population doubling time and colony-forming efficiency than other combinations of feeder cells with LIFs. Rabbit ESCs derived and maintained on both conditions displayed typical ESC characteristics, including ESC pluripotency marker expression (AP, Oct4, Sox2, Nanog, and SSEA4) and gene expression (Oct4, Sox2, Nanog, c-Myc, Klf4, and Dppa5), and the capacity to differentiate into three primary germ layers in vitro. The present work is the first attempt to establish rbESC lines using homologous feeder cells and recombinant rbLIF, by which the rbESCs were derived and maintained normally. These cell lines are unique resources and may facilitate the derivation of germ-line-competent rbESCs.
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Affiliation(s)
- Fei Xue
- Renova Life Inc., University of Maryland, TAP program, College Park, MD 20740, USA
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de Semir D, Maurisse R, Du F, Xu J, Yang X, Illek B, Gruenert DC. Generation of SV40-transformed rabbit tracheal-epithelial-cell-derived blastocyst by somatic cell nuclear transfer. Cell Tissue Res 2012; 347:357-67. [PMID: 22234514 DOI: 10.1007/s00441-011-1296-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 10/12/2011] [Indexed: 11/29/2022]
Abstract
The prospect of developing large animal models for the study of inherited diseases, such as cystic fibrosis (CF), through somatic cell nuclear transfer (SCNT) has opened up new opportunities for enhancing our understanding of disease pathology and for identifying new therapies. Thus, the development of species-specific in vitro cell systems that will provide broader insight into organ- and cell-type-specific functions relevant to the pathology of the disease is crucial. Studies have been undertaken to establish transformed rabbit airway epithelial cell lines that display differentiated features characteristic of the primary airway epithelium. This study describes the successful establishment and characterization of two SV40-transformed rabbit tracheal epithelial cell lines. These cell lines, 5RTEo- and 9RTEo-, express the CF transmembrane conductance regulator (CFTR) gene, retain epithelial-specific differentiated morphology and show CFTR-based cAMP-dependent Cl(-) ion transport across the apical membrane of a confluent monolayer. Immunocytochemical analysis indicates the presence of airway cytokeratins and tight-junction proteins in the 9RTEo- cell line after multiple generations. However, the tight junctions appear to diminish in their efficacy in both cell lines after at least 100 generations. Initial SCNT studies with the 9RTEo- cells have revealed that SV40-transformed rabbit airway epithelial donor cells can be used to generate blastocysts. These cell systems provide valuable models for studying the developmental and metabolic modulation of CFTR gene expression and rabbit airway epithelial cell biology.
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Affiliation(s)
- D de Semir
- California Pacific Medical Center Research Institute, San Francisco, Calif., USA
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Chen CH, Chang WF, Liu CC, Su HY, Shyue SK, Cheng WTK, Chen YE, Wu SC, Du F, Sung LY, Xu J. Spatial and temporal distribution of Oct-4 and acetylated H4K5 in rabbit embryos. Reprod Biomed Online 2012; 24:433-42. [PMID: 22381206 DOI: 10.1016/j.rbmo.2012.01.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 12/01/2011] [Accepted: 01/03/2012] [Indexed: 11/17/2022]
Abstract
Rabbit is a unique species to study human embryology; however, there are limited reports on the key transcription factors and epigenetic events of rabbit embryos. This study examined the Oct-4 and acetylated H4K5 (H4K5ac) patterns in rabbit embryos using immunochemistry staining. The average intensity of the Oct-4 signal in the nuclei of the whole embryo spiked upon fertilization, then decreased until the 8-cell stage and increased afterwards until the compact morula (CM) stage. It decreased thereafter from the CM stage to the early blastocyst (EB) stage, with a minimum at the expanded blastocyst (EXPB) stage and came back to a level similar to that of the CM-stage embryos in the hatching blastocysts (HB). The Oct-4 signal was observed in both the inner cell mass (ICM) and the trophectoderm (TE) cells of blastocysts. The average H4K5ac signal intensity of the whole embryo increased upon fertilization, started to decrease at the 4-cell stage, reached a minimum at the 8-cell stage, increased again at the EXPB stage and peaked at the HB stage. While TE cells maintained similar levels of H4K5ac throughout the blastocyst stages, ICM cells of HB showed higher levels of H4K5ac than those of EB and EXPB. Understanding key genetic and epigenetic events during early embryo development will help to identify factors contributing to embryo losses and consequently improve embryo survival rates. As a preferred laboratory species for many human disease studies such as atherosclerosis, rabbit is also a pioneer species in the development of several embryo biotechnologies, such as IVF, transgenesis, animal cloning, embryo cryopreservation and embryonic stem cells. However, there are limited reports on key transcription factors and epigenetic events of rabbit embryos. In the present study, we documented the temporal and spatial distribution of Oct-4 protein and H4K5 acetylation during early embryo development using the immunostaining approach. We also compared the patterns of these two important biomarkers between the inner cell mass (ICM) and the trophectoderm (TE) cells in blastocyst-stage embryos. Our findings suggest that a combination of Oct-4, H4K5ac and possibly other biomarkers such as Cdx-2 is needed to accurately identify different lineages of cells in morula and blastocyst stage rabbit embryos. Importantly, we revealed a novel wave of Oct-4 intensity change in the ICM cells of rabbit blastocysts. The signal was high at the early blastocyst stage, reached a minimum at the expanded blastocyst stage and returned to a high level at the hatching blastocyst stage. We hypothesize that the signal may have reflected the regulation of Oct-4 through enhancer switching and therefore may be related to cell lineage formation in rabbit embryos. These findings enrich our understanding on key genetic and epigenetic programming events during early embryo development in rabbits.
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Affiliation(s)
- Chien-Hong Chen
- Institute of Biotechnology, National Taiwan University, Taipei, Taiwan, ROC
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Tian J, Song J, Li H, Yang D, Li X, Ouyang H, Lai L. Effect of donor cell type on nuclear remodelling in rabbit somatic cell nuclear transfer embryos. Reprod Domest Anim 2011; 47:544-52. [PMID: 22034900 DOI: 10.1111/j.1439-0531.2011.01915.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cloned rabbits have been produced for many years by somatic cell nuclear transfer (SCNT). The efficiency of cloning by SCNT, however, has remained extremely low. Most cloned embryos degenerate in utero, and the few that develop to term show a high incidence of post-natal death and abnormalities. The cell type used for donor nuclei is an important factor in nuclear transfer (NT). As reported previously, NT embryos reconstructed with fresh cumulus cells (CC-embryos) have better developmental potential than those reconstructed with foetal fibroblasts (FF-embryos) in vivo and in vitro. The reason for this disparity in developmental capacity is still unknown. In this study, we compared active demethylation levels and morphological changes between the nuclei of CC-embryos and FF-embryos shortly after activation. Anti-5-methylcytosine immunofluorescence of in vivo-fertilized and cloned rabbit embryos revealed that there was no detectable active demethylation in rabbit zygotes or NT-embryos derived from either fibroblasts or CC. In the process of nuclear remodelling, however, the proportion of nuclei with abnormal appearance in FF-embryos was significantly higher than that in CC-embryos during the first cell cycle. Our study demonstrates that the nuclear remodelling abnormality of cloned rabbit embryos may be one important factor for the disparity in developmental success between CC-embryos and FF-embryos.
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Affiliation(s)
- J Tian
- College of Animal Science and Veterinary Medicine, Jilin University, Changchun, Jilin, China
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Sung LY, Chen CH, Xu J, Lin TA, Su HY, Chang WF, Liu CC, Sung YS, Cheng WTK, Zhang J, Tian XC, Ju JC, Chen YE, Wu SC, Du F. Follicular oocytes better support development in rabbit cloning than oviductal oocytes. Cell Reprogram 2011; 13:503-12. [PMID: 22029417 DOI: 10.1089/cell.2011.0030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
This study was conducted to determine the effect of rabbit oocytes collected from ovaries or oviducts on the developmental potential of nuclear transplant embryos. Donor nuclei were obtained from adult skin fibroblasts, cumulus cells, and embryonic blastomeres. Rabbit oocytes were flushed from the oviducts (oviductal oocytes) or aspirated from the ovaries (follicular oocytes) of superovulated does at 10, 11, or 12 h post-hCG injection. The majority of collected oocytes were still attached to the sites of ovulation on the ovaries. We found that follicular oocytes had a significantly higher rate of fusion with nuclear donor cells than oviductal oocytes. There was no difference in the cleavage rate between follicular and oviductal groups, but morula and blastocyst development was significantly higher in the follicular group than in the oviductal group. Two live clones were produced in follicular group using blastomere and cumulus nuclear donors, whereas one live clone was produced in the oviductal group using a cumulus nuclear donor. These results demonstrate that cloned rabbit embryos derived from follicular oocytes have better developmental competence than those derived from oviductal oocytes.
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Affiliation(s)
- Li-Ying Sung
- Institute of Biotechnology, National Taiwan University, Taipei, Taiwan, Republic of China
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Lin T, Chen C, Sung L, Carter M, Chen Y, Du F, Ju J, Xu J. Open-pulled straw vitrification differentiates cryotolerance of in vitro cultured rabbit embryos at the eight-cell stage. Theriogenology 2011; 75:760-8. [DOI: 10.1016/j.theriogenology.2010.10.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 10/09/2010] [Accepted: 10/09/2010] [Indexed: 10/18/2022]
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Ma LB, Cai L, Li JJ, Chen XL, Ji FY. Two-staged nuclear transfer can enhance the developmental ability of goat-sheep interspecies nuclear transfer embryos in vitro. In Vitro Cell Dev Biol Anim 2010; 47:95-103. [PMID: 21082282 DOI: 10.1007/s11626-010-9363-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 10/19/2010] [Indexed: 01/07/2023]
Abstract
The technique of interspecies somatic cell nuclear transfer, in which interspecies cloned embryos can be reconstructed by using domestic animal oocytes as nuclear recipients and endangered animal or human somatic cells as nuclear donors, can afford more opportunities in endangered animal rescue and human tissue transplantation, but the application of this technique is limited by extremely low efficiency which may be attributed to donor nucleus not fully reprogrammed by xenogenic cytoplasm. In this study, goat fetal fibroblasts (GFFs) were used as nuclear donors, in vitro-matured sheep oocytes were used as nuclear recipients, and a two-stage nuclear transfer procedure was performed to improve the developmental ability of goat-sheep interspecies clone embryos. In the first stage nuclear transfer (FSNT), GFFs were injected into the ooplasm of enucleated sheep metaphase-II oocytes, then non-activated reconstructed embryos were cultured in vitro, so that the donor nucleus could be exposed to the ooplasm for a period of time. Subsequently, in the second stage nuclear transfer, FSNT-derived non-activated reconstructed embryo was centrifuged, and the donor nucleus was then transferred into another freshly enucleated sheep oocyte. Compared with the one-stage nuclear transfer, two-stage nuclear transfer could significantly enhance the blastocyst rate of goat-sheep interspecies clone embryos, and this result indicated that longtime exposure to xenogenic ooplasm benefits the donor nucleus to be reprogrammed. The two-stage nuclear transfer procedure has two advantages, one is that the donor nucleus can be exposed to the ooplasm for a long time, the other is that the problem of oocyte aging can be solved.
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Affiliation(s)
- Li-Bing Ma
- School of Mathematics, Physics and Biological Engineering, Inner Mongolia University of Science & Technology, Baotou, Inner Mongolia, China.
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