1
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Olaya I, Burgess SM, Rog O. Formation and resolution of meiotic chromosome entanglements and interlocks. J Cell Sci 2024; 137:jcs262004. [PMID: 38985540 PMCID: PMC11267460 DOI: 10.1242/jcs.262004] [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] [Indexed: 07/12/2024] Open
Abstract
Interactions between parental chromosomes during the formation of gametes can lead to entanglements, entrapments and interlocks between unrelated chromosomes. If unresolved, these topological constraints can lead to misregulation of exchanges between chromosomes and to chromosome mis-segregation. Interestingly, these configurations are largely resolved by the time parental chromosomes are aligned during pachytene. In this Review, we highlight the inevitability of topologically complex configurations and discuss possible mechanisms to resolve them. We focus on the dynamic nature of a conserved chromosomal interface - the synaptonemal complex - and the chromosome movements that accompany meiosis as potential mechanisms to resolve topological constraints. We highlight the advantages of the nematode Caenorhabditis elegans for understanding biophysical features of the chromosome axis and synaptonemal complex that could contribute to mechanisms underlying interlock resolution. In addition, we highlight advantages of using the zebrafish, Danio rerio, as a model to understand how entanglements and interlocks are avoided and resolved.
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Affiliation(s)
- Iván Olaya
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA 95616, USA
- Integrative Genetics and Genomics Graduate Group, University of California Davis, Davis, CA 95616, USA
| | - Sean M. Burgess
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA 95616, USA
| | - Ofer Rog
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT 84112, USA
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2
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Islam KN, Ajao A, Venkataramani K, Rivera J, Pathania S, Henke K, Siegfried KR. The RNA-binding protein Adad1 is necessary for germ cell maintenance and meiosis in zebrafish. PLoS Genet 2023; 19:e1010589. [PMID: 37552671 PMCID: PMC10437952 DOI: 10.1371/journal.pgen.1010589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 08/18/2023] [Accepted: 07/06/2023] [Indexed: 08/10/2023] Open
Abstract
The double stranded RNA binding protein Adad1 (adenosine deaminase domain containing 1) is a member of the adenosine deaminase acting on RNAs (Adar) protein family with germ cell-specific expression. In mice, Adad1 is necessary for sperm differentiation, however its function outside of mammals has not been investigated. Here, through an N-ethyl-N-nitrosourea (ENU) based forward genetic screen, we identified an adad1 mutant zebrafish line that develops as sterile males. Further histological examination revealed complete lack of germ cells in adult mutant fish, however germ cells populated the gonad, proliferated, and entered meiosis in larval and juvenile fish. Although meiosis was initiated in adad1 mutant testes, the spermatocytes failed to progress beyond the zygotene stage. Thus, Adad1 is essential for meiosis and germline maintenance in zebrafish. We tested if spermatogonial stem cells were affected using nanos2 RNA FISH and a label retaining cell (LRC) assay, and found that the mutant testes had fewer LRCs and nanos2-expressing cells compared to wild-type siblings, suggesting that failure to maintain the spermatogonial stem cells resulted in germ cell loss by adulthood. To identify potential molecular processes regulated by Adad1, we sequenced bulk mRNA from mutants and wild-type testes and found mis-regulation of genes involved in RNA stability and modification, pointing to a potential broader role in post-transcriptional regulation. Our findings suggest that the RNA regulatory protein Adad1 is required for fertility through regulation of spermatogonial stem cell maintenance in zebrafish.
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Affiliation(s)
- Kazi Nazrul Islam
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Anuoluwapo Ajao
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Kavita Venkataramani
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Joshua Rivera
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, United States of America
- Center for Personalized Cancer Therapy, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Shailja Pathania
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, United States of America
- Center for Personalized Cancer Therapy, University of Massachusetts Boston, Boston, Massachusetts, United States of America
| | - Katrin Henke
- Department of Orthopaedics, Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Kellee Renee Siegfried
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, United States of America
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3
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Ye D, Liu T, Li Y, Wang Y, Hu W, Zhu Z, Sun Y. Identification of fish spermatogenic cells through high-throughput immunofluorescence against testis with an antibody set. Front Endocrinol (Lausanne) 2023; 14:1044318. [PMID: 37077350 PMCID: PMC10106697 DOI: 10.3389/fendo.2023.1044318] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 03/23/2023] [Indexed: 04/05/2023] Open
Abstract
Image-based identification and quantification of different types of spermatogenic cells is of great importance, not only for reproductive studies but also for genetic breeding. Here, we have developed antibodies against spermatogenesis-related proteins in zebrafish (Danio rerio), including Ddx4, Piwil1, Sycp3, and Pcna, and a high-throughput method for immunofluorescence analysis of zebrafish testicular sections. By immunofluorescence analysis of zebrafish testes, our results demonstrate that the expression of Ddx4 decreases progressively during spermatogenesis, Piwil1 is strongly expressed in type A spermatogonia and moderately expressed in type B spermatogonia, and Sycp3 has distinct expression patterns in different subtypes of spermatocytes. Additionally, we observed polar expression of Sycp3 and Pcna in primary spermatocytes at the leptotene stage. By a triple staining of Ddx4, Sycp3, and Pcna, different types/subtypes of spermatogenic cells were easily characterized. We further demonstrated the practicality of our antibodies in other fish species, including Chinese rare minnow (Gobiocypris rarus), common carp (Cyprinus carpio), blunt snout bream (Megalobrama amblycephala), rice field eel (Monopterus albus) and grass carp (Ctenopharyngodon idella). Finally, we proposed an integrated criterion for identifying different types/subtypes of spermatogenic cells in zebrafish and other fishes using this high-throughput immunofluorescence approach based on these antibodies. Therefore, our study provides a simple, practical, and efficient tool for the study of spermatogenesis in fish species.
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Affiliation(s)
- Ding Ye
- State Key Laboratory of Freshwater Ecology and Biotechnology, Hubei Hongshan Laboratory, Institute of Hydrobiology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Wuhan, China
| | - Tao Liu
- College of Fisheries and Life Science, Dalian Ocean University, Dalian, China
| | - Yongming Li
- State Key Laboratory of Freshwater Ecology and Biotechnology, Hubei Hongshan Laboratory, Institute of Hydrobiology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Wuhan, China
| | - Yaping Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Hubei Hongshan Laboratory, Institute of Hydrobiology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Wuhan, China
| | - Wei Hu
- State Key Laboratory of Freshwater Ecology and Biotechnology, Hubei Hongshan Laboratory, Institute of Hydrobiology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Wuhan, China
| | - Zuoyan Zhu
- State Key Laboratory of Freshwater Ecology and Biotechnology, Hubei Hongshan Laboratory, Institute of Hydrobiology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Wuhan, China
| | - Yonghua Sun
- State Key Laboratory of Freshwater Ecology and Biotechnology, Hubei Hongshan Laboratory, Institute of Hydrobiology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Wuhan, China
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4
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Kim HJ, Liu C, Dernburg AF. How and Why Chromosomes Interact with the Cytoskeleton during Meiosis. Genes (Basel) 2022; 13:genes13050901. [PMID: 35627285 PMCID: PMC9140367 DOI: 10.3390/genes13050901] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 05/09/2022] [Accepted: 05/12/2022] [Indexed: 11/28/2022] Open
Abstract
During the early meiotic prophase, connections are established between chromosomes and cytoplasmic motors via a nuclear envelope bridge, known as a LINC (linker of nucleoskeleton and cytoskeleton) complex. These widely conserved links can promote both chromosome and nuclear motions. Studies in diverse organisms have illuminated the molecular architecture of these connections, but important questions remain regarding how they contribute to meiotic processes. Here, we summarize the current knowledge in the field, outline the challenges in studying these chromosome dynamics, and highlight distinctive features that have been characterized in major model systems.
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Affiliation(s)
- Hyung Jun Kim
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA;
| | - Chenshu Liu
- Howard Hughes Medical Institute, 4000 Jones Bridge Road, Chevy Chase, MD 20815-6789, USA;
| | - Abby F. Dernburg
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA;
- Howard Hughes Medical Institute, 4000 Jones Bridge Road, Chevy Chase, MD 20815-6789, USA;
- Correspondence:
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5
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Mytlis A, Kumar V, Qiu T, Deis R, Hart N, Levy K, Masek M, Shawahny A, Ahmad A, Eitan H, Nather F, Adar-Levor S, Birnbaum RY, Elia N, Bachmann-Gagescu R, Roy S, Elkouby YM. Control of meiotic chromosomal bouquet and germ cell morphogenesis by the zygotene cilium. Science 2022; 376:eabh3104. [PMID: 35549308 DOI: 10.1126/science.abh3104] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A hallmark of meiosis is chromosomal pairing, which requires telomere tethering and rotation on the nuclear envelope via microtubules, driving chromosome homology searches. Telomere pulling toward the centrosome forms the "zygotene chromosomal bouquet". Here, we identified the "zygotene cilium" in oocytes. This cilium provides a cable system for the bouquet machinery, extending throughout the germline cyst. Using zebrafish mutants and live manipulations, we demonstrate that the cilium anchors the centrosome to counterbalance telomere pulling. The cilium is essential for bouquet and synaptonemal complex formation, oogenesis, ovarian development, and fertility. Thus, a cilium represents a conserved player in zebrafish and mouse meiosis, which sheds light on reproductive aspects in ciliopathies, and suggests that cilia can control chromosomal dynamics.
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Affiliation(s)
- Avishag Mytlis
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Vineet Kumar
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Tao Qiu
- Institute of Molecular and Cell Biology, Proteos, 138673 Singapore
| | - Rachael Deis
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Neta Hart
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Karine Levy
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Markus Masek
- Department of Molecular Life Sciences, University of Zurich, 8057 Zurich, Switzerland.,Institute of Medical Genetics, University of Zurich, 8952 Schlieren, Switzerland
| | - Amal Shawahny
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Adam Ahmad
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Hagai Eitan
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Farouq Nather
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
| | - Shai Adar-Levor
- Departments of Life Sciences, Ben-Gurion University of the Negev, Beer Shave 84105, Israel
| | - Ramon Y Birnbaum
- Departments of Life Sciences, Ben-Gurion University of the Negev, Beer Shave 84105, Israel
| | - Natalie Elia
- Departments of Life Sciences, Ben-Gurion University of the Negev, Beer Shave 84105, Israel
| | - Ruxandra Bachmann-Gagescu
- Department of Molecular Life Sciences, University of Zurich, 8057 Zurich, Switzerland.,Institute of Medical Genetics, University of Zurich, 8952 Schlieren, Switzerland
| | - Sudipto Roy
- Institute of Molecular and Cell Biology, Proteos, 138673 Singapore.,Department of Biological Sciences, National University of Singapore, 117543 Singapore.,Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, 119288 Singapore
| | - Yaniv M Elkouby
- Department of Developmental Biology and Cancer Research, Hebrew University of Jerusalem Faculty of Medicine, Ein-Kerem Campus, Jerusalem 9112102, Israel.,Institute for Medical Research-Israel-Canada (IMRIC), Ein-Kerem Campus, Jerusalem 9112102, Israel
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6
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Charitonidou K, Panteris E, Ganias K. Balbiani body formation and cytoplasmic zonation during early oocyte development in two Clupeiform fishes. JOURNAL OF FISH BIOLOGY 2022; 100:1223-1232. [PMID: 35244939 DOI: 10.1111/jfb.15032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 02/25/2022] [Accepted: 03/01/2022] [Indexed: 06/14/2023]
Abstract
The Balbiani body (Bb) was examined in primary growth phase oocytes for the first time in two clupeoid fish species, the Mediterranean sardine, Sardina pilchardus, and the European anchovy, Engraulis encrasicolus, which belong to different families, Clupeidae and Engraulidae, respectively. Cytoplasmic morphological changes of early secondary growth oocytes were also investigated using confocal laser scanning microscopy, light and transmission electron microscopy. The ultrastructural observations showed that the two species develop a distinct spherical Bb. However, differences in the cytoplasm, mainly in the perinuclear area, were observed. Briefly, in sardine the Bb coexists with a thick perinuclear ring containing mitochondria, nuage, endoplasmic reticulum and small vesicles, while in anchovy this perinuclear ring is thinner, consisting of complexes of nuage and mitochondria. After the disassembly of the Bb, a prominent cytoplasmic zonation develops in the secondary growth oocytes of sardine and anchovy, although with different organelle distribution between the two species. Sardine oocytes exhibit a thick zone of endoplasmic reticulum around the nucleus, whereas in those of anchovy, a thick mitochondria-rich ring surrounding the nucleus was observed. The cytoplasmic characteristics, such as the perinuclear ring in primary oocytes in sardine and the mitochondria-rich ring of early secondary oocytes in anchovy, are also discernible in histological sections by standard procedures and could thus be used as indicators of maturity or imminent spawning period in routine light microscopy observations, providing a valuable tool for applied fisheries biology.
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Affiliation(s)
- Katerina Charitonidou
- Laboratory of Ichthyology, School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Emmanuel Panteris
- Department of Botany, School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Kostas Ganias
- Laboratory of Ichthyology, School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece
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7
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Dedukh D, Marta A, Janko K. Challenges and Costs of Asexuality: Variation in Premeiotic Genome Duplication in Gynogenetic Hybrids from Cobitis taenia Complex. Int J Mol Sci 2021; 22:ijms222212117. [PMID: 34830012 PMCID: PMC8622741 DOI: 10.3390/ijms222212117] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 10/25/2021] [Accepted: 11/04/2021] [Indexed: 02/07/2023] Open
Abstract
The transition from sexual reproduction to asexuality is often triggered by hybridization. The gametogenesis of many hybrid asexuals involves premeiotic genome endoreplication leading to bypass hybrid sterility and forming clonal gametes. However, it is still not clear when endoreplication occurs, how many gonial cells it affects and whether its rate differs among clonal lineages. Here, we investigated meiotic and premeiotic cells of diploid and triploid hybrids of spined loaches (Cypriniformes: Cobitis) that reproduce by gynogenesis. We found that in naturally and experimentally produced F1 hybrids asexuality is achieved by genome endoreplication, which occurs in gonocytes just before entering meiosis or, rarely, one or a few divisions before meiosis. However, genome endoreplication was observed only in a minor fraction of the hybrid's gonocytes, while the vast majority of gonocytes were unable to duplicate their genomes and consequently could not proceed beyond pachytene due to defects in bivalent formation. We also noted that the rate of endoreplication was significantly higher among gonocytes of hybrids from natural clones than of experimentally produced F1 hybrids. Thus, asexuality and hybrid sterility are intimately related phenomena and the transition from sexual reproduction to asexuality must overcome significant problems with genome incompatibilities with a possible impact on reproductive potential.
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Affiliation(s)
- Dmitrij Dedukh
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics of the CAS, Rumburská 89, 277 21 Liběchov, Czech Republic;
- Correspondence: (D.D.); (K.J.)
| | - Anatolie Marta
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics of the CAS, Rumburská 89, 277 21 Liběchov, Czech Republic;
- Department of Zoology, Faculty of Science, Charles University in Prague, 128 00 Prague, Czech Republic
- Institute of Zoology, MD-2028, Academiei 1, 2001 Chisinau, Moldova
| | - Karel Janko
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics of the CAS, Rumburská 89, 277 21 Liběchov, Czech Republic;
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic
- Correspondence: (D.D.); (K.J.)
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8
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Imai Y, Olaya I, Sakai N, Burgess SM. Meiotic Chromosome Dynamics in Zebrafish. Front Cell Dev Biol 2021; 9:757445. [PMID: 34692709 PMCID: PMC8531508 DOI: 10.3389/fcell.2021.757445] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 09/14/2021] [Indexed: 11/13/2022] Open
Abstract
Recent studies in zebrafish have revealed key features of meiotic chromosome dynamics, including clustering of telomeres in the bouquet configuration, biogenesis of chromosome axis structures, and the assembly and disassembly of the synaptonemal complex that aligns homologs end-to-end. The telomere bouquet stage is especially pronounced in zebrafish meiosis and sub-telomeric regions play key roles in mediating pairing and homologous recombination. In this review, we discuss the temporal progression of these events in meiosis prophase I and highlight the roles of proteins associated with meiotic chromosome architecture in homologous recombination. Finally, we discuss the interplay between meiotic mutants and gonadal sex differentiation and future research directions to study meiosis in living cells, including cell culture.
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Affiliation(s)
- Yukiko Imai
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan
| | - Ivan Olaya
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States.,Integrative Genetics and Genomics Graduate Group, University of California, Davis, Davis, CA, United States
| | - Noriyoshi Sakai
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan.,Department of Genetics, School of Life Sciences, SOKENDAI (The Graduate University for Advanced Studies), Mishima, Japan
| | - Sean M Burgess
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States
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9
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Islam KN, Modi MM, Siegfried KR. The Zebrafish Meiotic Cohesin Complex Protein Smc1b Is Required for Key Events in Meiotic Prophase I. Front Cell Dev Biol 2021; 9:714245. [PMID: 34434933 PMCID: PMC8381726 DOI: 10.3389/fcell.2021.714245] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 07/15/2021] [Indexed: 01/08/2023] Open
Abstract
The eukaryotic structural maintenance of chromosomes (SMC) proteins are involved in key processes of chromosome structure and dynamics. SMC1β was identified as a component of the meiotic cohesin complex in vertebrates, which aids in keeping sister chromatids together prior to segregation in meiosis II and is involved in association of homologous chromosomes in meiosis I. The role of SMC1β in meiosis has primarily been studied in mice, where mutant male and female mice are infertile due to germ cell arrest at pachytene and metaphase II stages, respectively. Here, we investigate the function of zebrafish Smc1b to understand the role of this protein more broadly in vertebrates. We found that zebrafish smc1b is necessary for fertility and has important roles in meiosis, yet has no other apparent roles in development. Therefore, smc1b functions primarily in meiosis in both fish and mammals. In zebrafish, we showed that smc1b mutant spermatocytes initiated telomere clustering in leptotene, but failed to complete this process and progress into zygotene. Furthermore, mutant spermatocytes displayed a complete failure of synapsis between homologous chromosomes and homolog pairing only occurred at chromosome ends. Interestingly, meiotic DNA double strand breaks occurred in the absence of Smc1b despite failed pairing and synapsis. Overall, our findings point to an essential role of Smc1b in the leptotene to zygotene transition during zebrafish spermatogenesis. In addition, ovarian follicles failed to form in smc1b mutants, suggesting an essential role in female meiosis as well. Our results indicate that there are some key differences in Smc1b requirement in meiosis among vertebrates: while Smc1b is not required for homolog pairing and synapsis in mice, it is essential for these processes in zebrafish.
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Affiliation(s)
- Kazi Nazrul Islam
- Biology Department, University of Massachusetts Boston, Boston, MA, United States
| | - Maitri Mitesh Modi
- Biology Department, University of Massachusetts Boston, Boston, MA, United States
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10
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Blokhina YP, Frees MA, Nguyen A, Sharifi M, Chu DB, Bispo K, Olaya I, Draper BW, Burgess SM. Rad21l1 cohesin subunit is dispensable for spermatogenesis but not oogenesis in zebrafish. PLoS Genet 2021; 17:e1009127. [PMID: 34138874 PMCID: PMC8291703 DOI: 10.1371/journal.pgen.1009127] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 07/20/2021] [Accepted: 05/04/2021] [Indexed: 01/12/2023] Open
Abstract
During meiosis I, ring-shaped cohesin complexes play important roles in aiding the proper segregation of homologous chromosomes. RAD21L is a meiosis-specific vertebrate cohesin that is required for spermatogenesis in mice but is dispensable for oogenesis in young animals. The role of this cohesin in other vertebrate models has not been explored. Here, we tested if the zebrafish homolog Rad21l1 is required for meiotic chromosome dynamics during spermatogenesis and oogenesis. We found that Rad21l1 localizes to unsynapsed chromosome axes. It is also found between the axes of the mature tripartite synaptonemal complex (SC) in both sexes. We knocked out rad21l1 and found that nearly all rad21l1-/- mutants develop as fertile males, suggesting that the mutation causes a defect in juvenile oogenesis, since insufficient oocyte production triggers female to male sex reversal in zebrafish. Sex reversal was partially suppressed by mutation of the checkpoint gene tp53, suggesting that the rad21l1 mutation activates Tp53-mediated apoptosis or arrest in females. This response, however, is not linked to a defect in repairing Spo11-induced double-strand breaks since deletion of spo11 does not suppress the sex reversal phenotype. Compared to tp53 single mutant controls, rad21l1-/- tp53-/- double mutant females produce poor quality eggs that often die or develop into malformed embryos. Overall, these results indicate that the absence of rad21l1-/- females is due to a checkpoint-mediated response and highlight a role for a meiotic-specific cohesin subunit in oogenesis but not spermatogenesis.
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Affiliation(s)
- Yana P. Blokhina
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
- Integrative Genetics and Genomics Graduate Group, University of California, Davis, California, United States of America
| | - Michelle A. Frees
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
| | - An Nguyen
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
| | - Masuda Sharifi
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
- Biochemistry, Molecular, Cellular, and Developmental Biology Graduate Group, University of California, Davis, California, United States of America
| | - Daniel B. Chu
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
- Integrative Genetics and Genomics Graduate Group, University of California, Davis, California, United States of America
| | - Kristi Bispo
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
| | - Ivan Olaya
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
- Integrative Genetics and Genomics Graduate Group, University of California, Davis, California, United States of America
| | - Bruce W. Draper
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
| | - Sean M. Burgess
- Department of Molecular and Cellular Biology, University of California, Davis, California, United States of America
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11
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Mytlis A, Elkouby YM. Live and Time-Lapse Imaging of Early Oogenesis and Meiotic Chromosomal Dynamics in Cultured Juvenile Zebrafish Ovaries. Methods Mol Biol 2021; 2218:137-155. [PMID: 33606229 DOI: 10.1007/978-1-0716-0970-5_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
Oocyte production is crucial for sexual reproduction. Recent findings in zebrafish and other established model organisms emphasize that the early steps of oogenesis involve the coordination of simultaneous and tightly sequential processes across cellular compartments and between sister cells. To fully understand the mechanistic framework of these coordinated processes, cellular and morphological analysis in high temporal resolution is required. Here, we provide a protocol for four-dimensional live time-lapse analysis of cultured juvenile zebrafish ovaries. We describe how multiple-stage oocytes can be simultaneously analyzed in single ovaries, and several ovaries can be processed in single experiments. In addition, we detail adequate conditions for quantitative image acquisition. Finally, we demonstrate that using this protocol, we successfully capture rapid meiotic chromosomal movements in early prophase for the first time in zebrafish oocytes, in four dimensions and in vivo. Our protocol expands the use of the zebrafish as a model system to understand germ cell and ovarian development in postembryonic stages.
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Affiliation(s)
- Avishag Mytlis
- Department of Developmental Biology and Cancer Research, The Hebrew University of Jerusalem, Faculty of Medicine, Institute for Medical Research - Israel-Canada (IMRIC), Jerusalem, Israel
| | - Yaniv M Elkouby
- Department of Developmental Biology and Cancer Research, The Hebrew University of Jerusalem, Faculty of Medicine, Institute for Medical Research - Israel-Canada (IMRIC), Jerusalem, Israel.
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12
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Imai Y, Saito K, Takemoto K, Velilla F, Kawasaki T, Ishiguro KI, Sakai N. Sycp1 Is Not Required for Subtelomeric DNA Double-Strand Breaks but Is Required for Homologous Alignment in Zebrafish Spermatocytes. Front Cell Dev Biol 2021; 9:664377. [PMID: 33842489 PMCID: PMC8033029 DOI: 10.3389/fcell.2021.664377] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/09/2021] [Indexed: 12/31/2022] Open
Abstract
In meiotic prophase I, homologous chromosomes are bound together by the synaptonemal complex, in which two axial elements are connected by transverse filaments and central element proteins. In human and zebrafish spermatocytes, homologous recombination and assembly of the synaptonemal complex initiate predominantly near telomeres. In mice, synapsis is not required for meiotic double-strand breaks (DSBs) and homolog alignment but is required for DSB repair; however, the interplay of these meiotic events in the context of peritelomeric bias remains unclear. In this study, we identified a premature stop mutation in the zebrafish gene encoding the transverse filament protein Sycp1. In sycp1 mutant zebrafish spermatocytes, axial elements were formed and paired at chromosome ends between homologs during early to mid-zygonema. However, they did not synapse, and their associations were mostly lost in late zygotene- or pachytene-like stages. In sycp1 mutant spermatocytes, γH2AX signals were observed, and Dmc1/Rad51 and RPA signals appeared predominantly near telomeres, resembling wild-type phenotypes. We observed persistent localization of Hormad1 along the axis in sycp1 mutant spermatocytes, while the majority of Iho1 signals appeared and disappeared with kinetics similar to those in wild-type spermatocytes. Notably, persistent Iho1 foci were observed in spo11 mutant spermatocytes, suggesting that Iho1 dissociation from axes occurs in a DSB-dependent manner. Our results demonstrated that Sycp1 is not required for peritelomeric DSB formation but is necessary for complete pairing of homologs in zebrafish meiosis.
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Affiliation(s)
- Yukiko Imai
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan
| | - Kenji Saito
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan
| | - Kazumasa Takemoto
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan
| | - Fabien Velilla
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan
| | - Toshihiro Kawasaki
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan.,Department of Genetics, School of Life Sciences, SOKENDAI (The Graduate University for Advanced Studies), Mishima, Japan
| | - Kei-Ichiro Ishiguro
- Department of Chromosome Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Japan
| | - Noriyoshi Sakai
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan.,Department of Genetics, School of Life Sciences, SOKENDAI (The Graduate University for Advanced Studies), Mishima, Japan
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13
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Mixing and Matching Chromosomes during Female Meiosis. Cells 2020; 9:cells9030696. [PMID: 32178277 PMCID: PMC7140621 DOI: 10.3390/cells9030696] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 03/08/2020] [Accepted: 03/11/2020] [Indexed: 01/17/2023] Open
Abstract
Meiosis is a key event in the manufacturing of an oocyte. During this process, the oocyte creates a set of unique chromosomes by recombining paternal and maternal copies of homologous chromosomes, and by eliminating one set of chromosomes to become haploid. While meiosis is conserved among sexually reproducing eukaryotes, there is a bewildering diversity of strategies among species, and sometimes within sexes of the same species, to achieve proper segregation of chromosomes. Here, we review the very first steps of meiosis in females, when the maternal and paternal copies of each homologous chromosomes have to move, find each other and pair. We explore the similarities and differences observed in C. elegans, Drosophila, zebrafish and mouse females.
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14
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Blokhina YP, Olaya I, Burgess SM. Preparation of Meiotic Chromosome Spreads from Zebrafish Spermatocytes. J Vis Exp 2020. [PMID: 32202531 DOI: 10.3791/60671] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Meiosis is the key cellular process required to create haploid gametes for sexual reproduction. Model organisms have been instrumental in understanding the chromosome events that take place during meiotic prophase, including the pairing, synapsis, and recombination events that ensure proper chromosome segregation. While the mouse has been an important model for understanding the molecular mechanisms underlying these processes, not all meiotic events in this system are analogous to human meiosis. We recently demonstrated the exciting potential of the zebrafish as a model of human spermatogenesis. Here we describe, in detail, our methods to visualize meiotic chromosomes and associated proteins in chromosome spread preparations. These preparations have the advantage of allowing high resolution analysis of chromosome structures. First, we describe the procedure for dissecting testes from adult zebrafish, followed by cell dissociation, lysis, and spreading of the chromosomes. Next, we describe the procedure for detecting the localization of meiotic chromosome proteins, by immunofluorescence detection, and nucleic acid sequences, by fluorescence in situ hybridization (FISH). These techniques comprise a useful set of tools for the cytological analysis of meiotic chromatin architecture in the zebrafish system. Researchers in the zebrafish community should be able to quickly master these techniques and incorporate them into their standard analyses of reproductive function.
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Affiliation(s)
- Yana P Blokhina
- Department of Molecular and Cellular Biology, University of California, Davis; Integrative Genetics and Genomics Graduate Group, University of California, Davis
| | - Ivan Olaya
- Department of Molecular and Cellular Biology, University of California, Davis; Integrative Genetics and Genomics Graduate Group, University of California, Davis
| | - Sean M Burgess
- Department of Molecular and Cellular Biology, University of California, Davis;
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15
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Sycp2 is essential for synaptonemal complex assembly, early meiotic recombination and homologous pairing in zebrafish spermatocytes. PLoS Genet 2020; 16:e1008640. [PMID: 32092049 PMCID: PMC7062287 DOI: 10.1371/journal.pgen.1008640] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 03/09/2020] [Accepted: 01/29/2020] [Indexed: 12/16/2022] Open
Abstract
Meiotic recombination is essential for faithful segregation of homologous chromosomes during gametogenesis. The progression of recombination is associated with dynamic changes in meiotic chromatin structures. However, whether Sycp2, a key structural component of meiotic chromatin, is required for the initiation of meiotic recombination is still unclear in vertebrates. Here, we describe that Sycp2 is required for assembly of the synaptonemal complex and early meiotic events in zebrafish spermatocytes. Our genetic screening by N-ethyl-N-nitrosourea mutagenesis revealed that ietsugu (its), a mutant zebrafish line with an aberrant splice site in the sycp2 gene, showed a defect during meiotic prophase I. The its mutation appeared to be a hypomorphic mutation compared to sycp2 knockout mutations generated by TALEN mutagenesis. Taking advantage of these sycp2 hypomorphic and knockout mutant lines, we demonstrated that Sycp2 is required for the assembly of the synaptonemal complex that is initiated in the vicinity of telomeres in wild-type zebrafish spermatocytes. Accordingly, homologous pairing, the foci of the meiotic recombinases Dmc1/Rad51 and RPA, and γH2AX signals were largely diminished in sycp2 knockout spermatocytes. Taken together, our data indicate that Sycp2 plays a critical role in not only the assembly of the synaptonemal complex, but also early meiotic recombination and homologous pairing, in vertebrates.
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16
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Blokhina YP, Nguyen AD, Draper BW, Burgess SM. The telomere bouquet is a hub where meiotic double-strand breaks, synapsis, and stable homolog juxtaposition are coordinated in the zebrafish, Danio rerio. PLoS Genet 2019; 15:e1007730. [PMID: 30653507 PMCID: PMC6336226 DOI: 10.1371/journal.pgen.1007730] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 10/01/2018] [Indexed: 11/30/2022] Open
Abstract
Meiosis is a cellular program that generates haploid gametes for sexual reproduction. While chromosome events that contribute to reducing ploidy (homologous chromosome pairing, synapsis, and recombination) are well conserved, their execution varies across species and even between sexes of the same species. The telomere bouquet is a conserved feature of meiosis that was first described nearly a century ago, yet its role is still debated. Here we took advantage of the prominent telomere bouquet in zebrafish, Danio rerio, and super-resolution microscopy to show that axis morphogenesis, synapsis, and the formation of double-strand breaks (DSBs) all take place within the immediate vicinity of telomeres. We established a coherent timeline of events and tested the dependence of each event on the formation of Spo11-induced DSBs. First, we found that the axis protein Sycp3 loads adjacent to telomeres and extends inward, suggesting a specific feature common to all telomeres seeds the development of the axis. Second, we found that newly formed axes near telomeres engage in presynaptic co-alignment by a mechanism that depends on DSBs, even when stable juxtaposition of homologous chromosomes at interstitial regions is not yet evident. Third, we were surprised to discover that ~30% of telomeres in early prophase I engage in associations between two or more chromosome ends and these interactions decrease in later stages. Finally, while pairing and synapsis were disrupted in both spo11 males and females, their reproductive phenotypes were starkly different; spo11 mutant males failed to produce sperm while females produced offspring with severe developmental defects. Our results support zebrafish as an important vertebrate model for meiosis with implications for differences in fertility and genetically derived birth defects in males and females. Inherent to reproduction is the transmission of genetic information from one generation to the next. In sexually reproducing organisms, each parent contributes an equal amount of genetic information, packaged in chromosomes, to the offspring. Diploid organisms, like humans, have two copies of every chromosome, while their haploid gametes (e.g. eggs and sperm) have only one. This reduction in ploidy depends on the segregation of chromosomes during meiosis, resulting in gametes with one copy of each chromosome. Missegregation of the chromosomes in the parents leads to abnormal chromosome numbers in the offspring, which is usually lethal or has detrimental developmental effects. While it has been known for over a century that homologous chromosomes pair and recombine to facilitate proper segregation, how homologs find their partners has remained elusive. A structure that has been central to the discussion of homolog pairing is the bouquet, or the dynamic clustering of telomeres during early stages of meiosis. Here we use zebrafish to show that the telomere bouquet is the site where key events leading to homologous chromosome pairing are coordinated. Furthermore, we show that deletion of spo11, a gene required for proper recombination in most studied organisms, resulted in very different effects in males and females where males were sterile while females produced deformed progeny.
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Affiliation(s)
- Yana P. Blokhina
- Department of Molecular and Cellular Biology, University of California, Davis, CA, United States of America
- Integrative Genetics and Genomics Graduate Group, University of California, Davis, CA, United States of America
| | - An D. Nguyen
- Department of Molecular and Cellular Biology, University of California, Davis, CA, United States of America
| | - Bruce W. Draper
- Department of Molecular and Cellular Biology, University of California, Davis, CA, United States of America
| | - Sean M. Burgess
- Department of Molecular and Cellular Biology, University of California, Davis, CA, United States of America
- * E-mail:
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17
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Webster KA, Henke K, Ingalls DM, Nahrin A, Harris MP, Siegfried KR. Cyclin-dependent kinase 21 is a novel regulator of proliferation and meiosis in the male germline of zebrafish. Reproduction 2018; 157:383-398. [PMID: 30763280 PMCID: PMC6489137 DOI: 10.1530/rep-18-0386] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 02/14/2019] [Indexed: 01/07/2023]
Abstract
Germ cell differentiation and maintenance relies on complex regulation of mitotic and meiotic progression. Cyclin-dependent kinases (CDKs) and their activating cyclin partners are known to have specialized roles in regulating cell cycle progression across tissues, including germ cells. Very little is known about CDK/cyclin function in zebrafish or the regulation of germ cell maintenance and differentiation. In a forward genetic screen for gonadogenesis defects in zebrafish, a mutation disrupting cdk21 (cyclin-dependent kinase 21) was identified, which caused gonad hypoplasia, reduced fertility and failure of female sex specification. The cdk21 gene is unique to fishes, though the encoded protein is related to the D-cyclin partners Cdk4 and Cdk6, which are known G1 cell cycle regulators. In the testis, cdk21 mutant germ cells exhibited cell cycle defects such as diminished proliferation, prolonged meiosis and delayed sperm differentiation. Furthermore, cdk21 mutants failed to maintain germ cells following breeding. Based on these findings, we propose that cdk21 regulates spermatogonial proliferation, progression through meiosis and germline stem cell activation in the testis. In addition, we investigated cdk4 and cdk6 in zebrafish development and found that each has distinct expression patterns in the gonads. Mutant analysis demonstrated that cdk6 was necessary for viability beyond larval stages. In contrast, cdk4 mutants were viable but were all male with low breeding success and sperm overabundance. Our analysis demonstrated that zebrafish harbor three genes of the cdk4/6 family, cdk4, cdk6 and cdk21, with cdk21 having an essential role in germ cell development in the testis.
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Affiliation(s)
- Kaitlyn A Webster
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, USA
| | - Katrin Henke
- Orthopaedic Research Laboratories, Boston Children's Hospital and Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
| | - Delaney M Ingalls
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, USA
| | - Adeeba Nahrin
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, USA
| | - Matthew P Harris
- Orthopaedic Research Laboratories, Boston Children's Hospital and Department of Genetics, Harvard Medical School, Boston, Massachusetts, USA
| | - Kellee R Siegfried
- Biology Department, University of Massachusetts Boston, Boston, Massachusetts, USA
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18
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Elkouby YM, Mullins MC. Coordination of cellular differentiation, polarity, mitosis and meiosis - New findings from early vertebrate oogenesis. Dev Biol 2017; 430:275-287. [PMID: 28666956 DOI: 10.1016/j.ydbio.2017.06.029] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 06/23/2017] [Accepted: 06/26/2017] [Indexed: 12/21/2022]
Abstract
A mechanistic dissection of early oocyte differentiation in vertebrates is key to advancing our knowledge of germline development, reproductive biology, the regulation of meiosis, and all of their associated disorders. Recent advances in the field include breakthroughs in the identification of germline stem cells in Medaka, in the cellular architecture of the germline cyst in mice, in a mechanistic dissection of chromosomal pairing and bouquet formation in meiosis in mice, in tracing oocyte symmetry breaking to the chromosomal bouquet of meiosis in zebrafish, and in the biology of the Balbiani body, a universal oocyte granule. Many of the major events in early oogenesis are universally conserved, and some are co-opted for species-specific needs. The chromosomal events of meiosis are of tremendous consequence to gamete formation and have been extensively studied. New light is now being shed on other aspects of early oocyte differentiation, which were traditionally considered outside the scope of meiosis, and their coordination with meiotic events. The emerging theme is of meiosis as a common groundwork for coordinating multifaceted processes of oocyte differentiation. In an accompanying manuscript we describe methods that allowed for investigations in the zebrafish ovary to contribute to these breakthroughs. Here, we review these advances mostly from the zebrafish and mouse. We discuss oogenesis concepts across established model organisms, and construct an inclusive paradigm for early oocyte differentiation in vertebrates.
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Affiliation(s)
- Yaniv M Elkouby
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Mary C Mullins
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
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19
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Elkouby YM, Jamieson-Lucy A, Mullins MC. Oocyte Polarization Is Coupled to the Chromosomal Bouquet, a Conserved Polarized Nuclear Configuration in Meiosis. PLoS Biol 2016; 14:e1002335. [PMID: 26741740 PMCID: PMC4704784 DOI: 10.1371/journal.pbio.1002335] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 11/19/2015] [Indexed: 12/02/2022] Open
Abstract
The source of symmetry breaking in vertebrate oocytes is unknown. Animal—vegetal oocyte polarity is established by the Balbiani body (Bb), a conserved structure found in all animals examined that contains an aggregate of specific mRNAs, proteins, and organelles. The Bb specifies the oocyte vegetal pole, which is key to forming the embryonic body axes as well as the germline in most vertebrates. How Bb formation is regulated and how its asymmetric position is established are unknown. Using quantitative image analysis, we trace oocyte symmetry breaking in zebrafish to a nuclear asymmetry at the onset of meiosis called the chromosomal bouquet. The bouquet is a universal feature of meiosis where all telomeres cluster to one pole on the nuclear envelope, facilitating chromosomal pairing and meiotic recombination. We show that Bb precursor components first localize with the centrosome to the cytoplasm adjacent to the telomere cluster of the bouquet. They then aggregate around the centrosome in a specialized nuclear cleft that we identified, assembling the early Bb. We show that the bouquet nuclear events and the cytoplasmic Bb precursor localization are mechanistically coordinated by microtubules. Thus the animal—vegetal axis of the oocyte is aligned to the nuclear axis of the bouquet. We further show that the symmetry breaking events lay upstream to the only known regulator of Bb formation, the Bucky ball protein. Our findings link two universal features of oogenesis, the Bb and the chromosomal bouquet, to oocyte polarization. We propose that a meiotic—vegetal center couples meiosis and oocyte patterning. Our findings reveal a novel mode of cellular polarization in meiotic cells whereby cellular and nuclear polarity are aligned. We further reveal that in zygotene nests, intercellular cytoplasmic bridges remain between oocytes and that the position of the cytoplasmic bridge coincides with the location of the centrosome meiotic—vegetal organizing center. These results suggest that centrosome positioning is set by the last mitotic oogonial division plane. Thus, oocytes are polarized in two steps: first, mitotic divisions preset the centrosome with no obvious polarization yet, then the meiotic—vegetal center forms at zygotene bouquet stages, when symmetry is, in effect, broken. This study traces symmetry breaking in zebrafish oocytes to a cellular organizer that controls the configuration of the meiotic polarized chromosomal bouquet, thereby coupling meiosis and oocyte patterning at the nexus of oocyte differentiation. In most vertebrates, an early event in egg development involves the establishment of the so-called animal—vegetal axis; this sets up the embryonic body axes and contributes to germ-line specification, and therefore, is key to embryonic development. The animal—vegetal axis is established during oogenesis by the Balbiani body (Bb), an aggregate of specific mRNAs, proteins, and mitochondria, which forms adjacent to the nucleus and ultimately defines one pole of the oocyte, the vegetal pole. Despite its universal conservation, how the Bb forms and how its position is determined is unknown. Here, we show that Bb formation is initiated at the onset of meiosis, and its position coincides with a previously known meiotic polarized nuclear configuration, the chromosomal bouquet, which gathers the chromosome ends, the telomeres, asymmetrically on the nuclear membrane to assist in homologous chromosome pairing. We reveal that a global cellular organizer functioning via microtubules generates the bouquet and aggregates the Bb precursors asymmetrically towards the centrosome. We determined that these events lie functionally upstream to the Bb regulator Bucky ball. Further upstream, we found that the centrosome appears prepositioned by an intercellular cytoplasmic bridge derived from the last presumptive cell division plane of the premeiotic oogonial cell. Thus, oocyte polarity and the chromosomal bouquet are linked through a common cellular polarization mechanism.
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Affiliation(s)
- Yaniv M. Elkouby
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Allison Jamieson-Lucy
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Mary C. Mullins
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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20
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Link J, Jahn D, Alsheimer M. Structural and functional adaptations of the mammalian nuclear envelope to meet the meiotic requirements. Nucleus 2015; 6:93-101. [PMID: 25674669 PMCID: PMC4615672 DOI: 10.1080/19491034.2015.1004941] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Numerous studies in the past years provided definite evidence that the nuclear envelope is much more than just a simple barrier. It rather constitutes a multifunctional platform combining structural and dynamic features to fulfill many fundamental functions such as chromatin organization, regulation of transcription, signaling, but also structural duties like maintaining general nuclear architecture and shape. One additional and, without doubt, highly impressive aspect is the recently identified key function of selected nuclear envelope components in driving meiotic chromosome dynamics, which in turn is essential for accurate recombination and segregation of the homologous chromosomes. Here, we summarize the recent work identifying new key players in meiotic telomere attachment and movement and discuss the latest advances in our understanding of the actual function of the meiotic nuclear envelope.
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Affiliation(s)
- Jana Link
- a Department of Cell and Developmental Biology ; Biocenter University Würzburg ; Würzburg , Germany
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