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Tian M, Cai X, Liu Y, Liucong M, Howard-Till R. A practical reference for studying meiosis in the model ciliate Tetrahymena thermophila. MARINE LIFE SCIENCE & TECHNOLOGY 2022; 4:595-608. [PMID: 37078080 PMCID: PMC10077211 DOI: 10.1007/s42995-022-00149-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Accepted: 09/28/2022] [Indexed: 05/03/2023]
Abstract
Meiosis is a critical cell division program that produces haploid gametes for sexual reproduction. Abnormalities in meiosis are often causes of infertility and birth defects (e.g., Down syndrome). Most organisms use a highly specialized zipper-like protein complex, the synaptonemal complex (SC), to guide and stabilize pairing of homologous chromosomes in meiosis. Although the SC is critical for meiosis in many eukaryotes, there are organisms that perform meiosis without a functional SC. However, such SC-less meiosis is poorly characterized. To understand the features of SC-less meiosis and its adaptive significance, the ciliated protozoan Tetrahymena was selected as a model. Meiosis research in Tetrahymena has revealed intriguing aspects of the regulatory programs utilized in its SC-less meiosis, yet additional efforts are needed for obtaining an in-depth comprehension of mechanisms that are associated with the absence of SC. Here, aiming at promoting a wider application of Tetrahymena for meiosis research, we introduce basic concepts and core techniques for studying meiosis in Tetrahymena and then suggest future directions for expanding the current Tetrahymena meiosis research toolbox. These methodologies could be adopted for dissecting meiosis in poorly characterized ciliates that might reveal novel features. Such data will hopefully provide insights into the function of the SC and the evolution of meiosis from a unique perspective. Supplementary Information The online version contains supplementary material available at 10.1007/s42995-022-00149-8.
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Affiliation(s)
- Miao Tian
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
- Institute of Human Genetics, CNRS, University of Montpellier, 34090 Montpellier, France
| | - Xia Cai
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Yujie Liu
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Mingmei Liucong
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237 China
| | - Rachel Howard-Till
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA USA
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Zhang J, Tian M, Chen K, Yan G, Xiong J, Miao W. Zfp1, a Cys2His2 zinc finger protein is required for meiosis initiation in Tetrahymena thermophila. Cell Cycle 2022; 21:1422-1433. [PMID: 35293272 PMCID: PMC9345619 DOI: 10.1080/15384101.2022.2053449] [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: 11/03/2022] Open
Abstract
Meiosis is an important and highly conserved process that occurs during eukaryotic sexual reproduction. Diverse mechanisms are responsible for meiosis initiation among eukaryotes, and transcription factors have been established to have an important role in many species. However, the specific function of transcription factors in initiating meiosis in ciliates is unknown. Here we show that a putative Cys2His2 zinc finger-containing transcription factor encoded by the ZFP1 gene is specifically expressed during sexual reproduction in Tetrahymena thermophila. Meiosis is not initiated in the cells lacking ZFP1. Transcriptome sequencing analyses reveal that Zfp1 is required for the expression of many meiosis-specific genes. Our results indicate that Zfp1 could be a transcriptional activator required for meiosis initiation in T. thermophila.
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Affiliation(s)
- Jing Zhang
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Miao Tian
- Department of Chromosome Biology and Max F. Perutz Laboratories, Center for Molecular Biology, University of Vienna, Vienna, Austria
| | - Kai Chen
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Guanxiong Yan
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China.,College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, Shanghai, China
| | - Jie Xiong
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Wei Miao
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China.,State Key Laboratory of Freshwater Ecology and Biotechnology of China, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China.,CAS Center for Excellence in Animal Evolution and Genetics, Kunming, Yunnan, China
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Identification and utilization of a mutated 60S ribosomal subunit coding gene as an effective and cost-efficient selection marker for Tetrahymena genetic manipulation. Int J Biol Macromol 2022; 204:1-8. [PMID: 35122796 DOI: 10.1016/j.ijbiomac.2022.01.188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/26/2022] [Accepted: 01/28/2022] [Indexed: 01/05/2023]
Abstract
Since the onset of molecular biology, the ciliate Tetrahymena thermophila has been one of the most convenient single-celled model eukaryotes for genetics, biochemistry, and cell biology. Particularly, thanks to the availability of several different selection markers, it is possible to knock out or knock in genes at multiple genetic loci simultaneously in Tetrahymena, which makes it an excellent model ciliate for tackling complex regulatory mechanisms. Despite these selection markers are efficient for genetic manipulation, the costly drugs used for selection have highlighted the urgent demand for an additional cost-efficient and effective selection marker. Here, we found that a mutated 60S ribosomal subunit component, RPL36A, confers T. thermophila with cycloheximide resistance. On top of that, we developed a cycloheximide cassette and explored suitable transformation and selection conditions. Using the new cassette, we obtained both knockout and knock-in strains successfully at a relatively low cost. This study also provided the first evidence that a cycloheximide resistance gene can be engineered as a selection marker to completely delete a gene from the highly-polyploid somatic nucleus in Tetrahymena.
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Abstract
The presence of meiosis, which is a conserved component of sexual reproduction, across organisms from all eukaryotic kingdoms, strongly argues that sex is a primordial feature of eukaryotes. However, extant meiotic structures and processes can vary considerably between organisms. The ciliated protist Tetrahymena thermophila, which diverged from animals, plants, and fungi early in evolution, provides one example of a rather unconventional meiosis. Tetrahymena has a simpler meiosis compared with most other organisms: It lacks both a synaptonemal complex (SC) and specialized meiotic machinery for chromosome cohesion and has a reduced capacity to regulate meiotic recombination. Despite this, it also features several unique mechanisms, including elongation of the nucleus to twice the cell length to promote homologous pairing and prevent recombination between sister chromatids. Comparison of the meiotic programs of Tetrahymena and higher multicellular organisms may reveal how extant meiosis evolved from proto-meiosis.
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Affiliation(s)
- Josef Loidl
- Department of Chromosome Biology, Max Perutz Labs, University of Vienna, Vienna, Austria
- * E-mail:
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Tian M, Agreiter C, Loidl J. Spatial constraints on chromosomes are instrumental to meiotic pairing. J Cell Sci 2020; 133:jcs253724. [PMID: 33172984 PMCID: PMC7725606 DOI: 10.1242/jcs.253724] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 10/29/2020] [Indexed: 01/10/2023] Open
Abstract
In most eukaryotes, the meiotic chromosomal bouquet (comprising clustered chromosome ends) provides an ordered chromosome arrangement that facilitates pairing and recombination between homologous chromosomes. In the protist Tetrahymena thermophila, the meiotic prophase nucleus stretches enormously, and chromosomes assume a bouquet-like arrangement in which telomeres and centromeres are attached to opposite poles of the nucleus. We have identified and characterized three meiosis-specific genes [meiotic nuclear elongation 1-3 (MELG1-3)] that control nuclear elongation, and centromere and telomere clustering. The Melg proteins interact with cytoskeletal and telomere-associated proteins, and probably repurpose them for reorganizing the meiotic prophase nucleus. A lack of sequence similarity between the Tetrahymena proteins responsible for telomere clustering and bouquet proteins of other organisms suggests that the Tetrahymena bouquet is analogous, rather than homologous, to the conserved eukaryotic bouquet. We also report that centromere clustering is more important than telomere clustering for homologous pairing. Therefore, we speculate that centromere clustering may have been the primordial mechanism for chromosome pairing in early eukaryotes.
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Affiliation(s)
- Miao Tian
- Department of Chromosome Biology, Max Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
| | - Christiane Agreiter
- Department of Chromosome Biology, Max Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
| | - Josef Loidl
- Department of Chromosome Biology, Max Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
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Sandhu R, Monge Neria F, Monge Neria J, Chen X, Hollingsworth NM, Börner GV. DNA Helicase Mph1 FANCM Ensures Meiotic Recombination between Parental Chromosomes by Dissociating Precocious Displacement Loops. Dev Cell 2020; 53:458-472.e5. [PMID: 32386601 DOI: 10.1016/j.devcel.2020.04.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 02/09/2020] [Accepted: 04/10/2020] [Indexed: 02/07/2023]
Abstract
Meiotic pairing between parental chromosomes (homologs) is required for formation of haploid gametes. Homolog pairing depends on recombination initiation via programmed double-strand breaks (DSBs). Although DSBs appear prior to pairing, the homolog, rather than the sister chromatid, is used as repair partner for crossing over. Here, we show that Mph1, the budding yeast ortholog of Fanconi anemia helicase FANCM, prevents precocious DSB strand exchange between sister chromatids before homologs have completed pairing. By dissociating precocious DNA displacement loops (D-loops) between sister chromatids, Mph1FANCM ensures high levels of crossovers and non-crossovers between homologs. Later-occurring recombination events are protected from Mph1-mediated dissociation by synapsis protein Zip1. Increased intersister repair in absence of Mph1 triggers a shift among remaining interhomolog events from non-crossovers to crossover-specific strand exchange, explaining Mph1's apparent anti-crossover function. Our findings identify temporal coordination between DSB strand exchange and homolog pairing as a critical determinant for recombination outcome.
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Affiliation(s)
- Rima Sandhu
- Center for Gene Regulation in Health and Disease and Department of Biological Sciences, Cleveland State University, Cleveland, OH 44115, USA
| | - Francisco Monge Neria
- Center for Gene Regulation in Health and Disease and Department of Biological Sciences, Cleveland State University, Cleveland, OH 44115, USA
| | - Jesús Monge Neria
- Center for Gene Regulation in Health and Disease and Department of Biological Sciences, Cleveland State University, Cleveland, OH 44115, USA
| | - Xiangyu Chen
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA
| | - Nancy M Hollingsworth
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA
| | - G Valentin Börner
- Center for Gene Regulation in Health and Disease and Department of Biological Sciences, Cleveland State University, Cleveland, OH 44115, USA; Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH 44106, USA; Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
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