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Hsaio S, Saglam N, Morrow D, Shain DH. Transcriptomic Profiling at the Maternal-to-Zygotic Transition in Leech, Helobdella austinensis. Genes (Basel) 2024; 15:283. [PMID: 38540342 PMCID: PMC10970458 DOI: 10.3390/genes15030283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 02/20/2024] [Accepted: 02/21/2024] [Indexed: 06/15/2024] Open
Abstract
The glossiphoniid leech, Helobdella austinensis, is an experimentally tractable member of the superphylum, Lophotrochozoa. Its large embryonic cells, stereotyped asymmetric cell divisions and ex vivo development capabilities makes it a favorable model for studying the molecular and cellular events of a representative spiralian. In this study, we focused on a narrow developmental time window of ~6-8 h, comprising stages just prior to and immediately following zygote deposition. Employing RNA-Seq methodology, we identified differentially expressed transcripts at this fundamental ontogenic boundary, known as the maternal-to-zygotic transition (MZT). Gene expression changes were characterized by the massive degradation of maternal RNAs (~45%) coupled with the rapid transcription of ~5000 zygotic genes (~20% of the genome) in the first mitotic cell cycle. The latter transcripts encoded a mixture of cell maintenance and regulatory proteins that predictably influence downstream developmental events.
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Affiliation(s)
- Samuel Hsaio
- Center for Computational and Integrative Biology, Rutgers The State University of New Jersey, Joint Health Sciences Center, 201 South Broadway, Camden, NJ 08103, USA
| | - Naim Saglam
- Department of Aquaculture and Fish Diseases, Fisheries Faculty, Firat University, 23200 Elazig, Türkiye
| | - David Morrow
- Biology Department, Rutgers The State University of New Jersey, Joint Health Sciences Center, 201 South Broadway, Camden, NJ 08103, USA
| | - Daniel H. Shain
- Center for Computational and Integrative Biology, Rutgers The State University of New Jersey, Joint Health Sciences Center, 201 South Broadway, Camden, NJ 08103, USA
- Biology Department, Rutgers The State University of New Jersey, Joint Health Sciences Center, 201 South Broadway, Camden, NJ 08103, USA
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2
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Nanos Is Expressed in Somatic and Germline Tissue during Larval and Post-Larval Development of the Annelid Alitta virens. Genes (Basel) 2022; 13:genes13020270. [PMID: 35205316 PMCID: PMC8871563 DOI: 10.3390/genes13020270] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/18/2022] [Accepted: 01/28/2022] [Indexed: 11/16/2022] Open
Abstract
Nanos is a translational regulator that is involved in germline development in a number of diverse animals and is also involved in somatic patterning in several model organisms, including insects. Neither germline development nor somatic stem cell lines/undifferentiated multipotent cells have been characterized in the development of the annelid Alitta virens, nor is the mechanism of germ/stem-line specification generally well-understood in annelids. Here, I have cloned an Avi-nanos ortholog from A. virens and determined the spatial and temporal expression of Nanos. The results revealed that transcripts of nanos are expressed during differentiation of multiple tissues, including those that are derived from the 2d and 4d cells. In late embryonic stages and during larval development, these transcripts are expressed in the presumptive brain, ventral nerve cord, mesodermal bands, putative primordial germ cells (PGCs), and developing foregut and hindgut. During metamorphosis of the nectochaete larva into a juvenile worm, a posterior growth zone consisting of nanos-positive cells is established, and the PGCs begin to migrate. Later, the PGCs stop migrating and form a cluster of four nanos-expressing cells located immediately behind the jaws (segments 4–5). During posterior regeneration following caudal amputation, a robust Avi-nanos expression appears de novo at the site of injury and further accompanies all steps of regeneration. The obtained data suggest that blastemal cells are mostly derived from cells of the segment adjacent to the amputation site; this is consistent with the idea that the cluster of PGCs do not participate in regeneration.
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3
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Anderson K, Pepinelli M, Kvist S. Natural occurrence of an experimental developmental phenotype in the leech Erpobdella punctata (Leidy 1870) (Annelida: Clitellata: Hirudinea). INVERTEBR REPROD DEV 2020. [DOI: 10.1080/07924259.2020.1784298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Kevin Anderson
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
- Department of Natural History, Royal Ontario Museum, Toronto, Canada
| | - Mateus Pepinelli
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
- Department of Natural History, Royal Ontario Museum, Toronto, Canada
| | - Sebastian Kvist
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Canada
- Department of Natural History, Royal Ontario Museum, Toronto, Canada
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4
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Kuo DH, Lai YT. On the origin of leeches by evolution of development. Dev Growth Differ 2018; 61:43-57. [PMID: 30393850 DOI: 10.1111/dgd.12573] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 10/01/2018] [Accepted: 10/02/2018] [Indexed: 12/19/2022]
Abstract
Leeches are a unique group of annelids arising from an ancestor that would be characterized as a freshwater oligochaete worm. Comparative biology of the oligochaetes and the leeches reveals that body plan changes in the oligochaete-to-leech transition probably occurred by addition or modification of the terminal steps in embryonic development and that they were likely driven by a change in the feeding behavior in the ancestor of leeches. In this review article, developmental changes that are associated with the evolution of several leech-specific traits are discussed. These include (1) the evolution of suckers, (2) the loss of chaetae, (3) the loss of septa, and (4) a fixed number of segments. An altered developmental fate of the teloblast is further proposed to be a key factor contributing to the fixation of the segment number, and the evolutionary change in teloblast development may also account for the loss of the ability to regenerate the lost body segments in the leech.
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Affiliation(s)
- Dian-Han Kuo
- Department of Life Science, National Taiwan University, Taipei, Taiwan
| | - Yi-Te Lai
- Department of Life Science, National Taiwan University, Taipei, Taiwan
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5
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Ponz‐Segrelles G, Bleidorn C, Aguado MT. Expression of
vasa
,
piwi
, and
nanos
during gametogenesis in
Typosyllis antoni
(Annelida, Syllidae). Evol Dev 2018; 20:132-145. [DOI: 10.1111/ede.12263] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Guillermo Ponz‐Segrelles
- Departamento de BiologíaFacultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
| | - Christoph Bleidorn
- Animal Evolution and BiodiversityGeorg‐August‐University GöttingenGöttingenGermany
| | - M. Teresa Aguado
- Departamento de BiologíaFacultad de CienciasUniversidad Autónoma de MadridCantoblancoMadridSpain
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6
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Xu R, Li Q, Yu H, Kong L. Oocyte maturation and origin of the germline as revealed by the expression of Nanos-like in the Pacific oyster Crassostrea gigas. Gene 2018; 663:41-50. [PMID: 29660519 DOI: 10.1016/j.gene.2018.04.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 03/07/2018] [Accepted: 04/09/2018] [Indexed: 01/19/2023]
Abstract
Nanos gene plays an important role in germline development in animals. However, the molecular mechanisms involved in germline development in Mollusca, the second largest animal phylum, are still poorly understood. Here we identified the Nanos orthologue from the Pacific oyster Crassostrea gigas (Cg-Nanos-like), and investigated the expression patterns of Nanos during gametogenesis and embryogenesis in C. gigas. Tissue expression analysis showed that Cg-Nanos-like was specifically expressed in female gonads. During the reproductive cycle, the expression of Cg-Nanos-like mRNA increased matching the seasonal development of the ovarian tissues in diploids, while the expression levels were significantly lower in the ovaries of sterile triploids compared to diploids. High expression of Cg-Nanos-like transcripts were detected in early embryonic stages, while the expression significantly dropped at gastrulation and was barely detectable in veliger stages. In situ hybridization showed that Cg-Nanos-like was expressed at different stages of developing oocytes, whereas positive signals were detected only in spermatogonia during the spermatogenic cycle. These findings indicated that Cg-Nanos-like was involved in the development of germ cells, and maintenance of oocyte maturation. In early embryogenesis, the transcripts were broadly expressed; following gastrulation, the expression was restricted to two cell clumps, which might be the putative primordial germ cells (PGCs) or their precursors. Based on the results, the formation of the PGCs in C. gigas was consistent with the model of transition from epigenesis to preformation.
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Affiliation(s)
- Rui Xu
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
| | - Qi Li
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China; Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, China.
| | - Hong Yu
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China.
| | - Lingfeng Kong
- Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, China
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7
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Kodama M, Yoshida M, Endo M, Kobayashi T, Oike A, Yasumasu S, Nakamura M. Nanos3 of the frog Rana rugosa: Molecular cloning and characterization. Dev Growth Differ 2018; 60:112-120. [PMID: 29405266 DOI: 10.1111/dgd.12421] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 12/03/2017] [Accepted: 12/08/2017] [Indexed: 11/30/2022]
Abstract
Nanos is expressed in the primordial germ cells (PGCs) and also the germ cells of a variety of organisms as diverse as Drosophila, medaka fish, Xenopus and mouse. In Nanos3-deficient mice, PGCs fail to incorporate into the gonad and the size of the testis and ovary is thereby dramatically reduced. To elucidate the role of Nanos in an amphibian species, we cloned Nanos3 cDNA from the testis of the R. rugosa frog. RT-PCR analysis showed strong expression of Nanos3 mRNA in the testis of adult R. rugosa frogs, but expression was not sexually dimorphic during gonadal differentiation. In Nanos3-knockdown tadpoles produced by the CRISPR/Cas9 system, the number of germ cells decreased dramatically in the gonads of both male and female tadpoles before sex determination and thereafter. This was confirmed by three dimensional imaging of wild-type and Nanos3 knockdown gonads using serial sections immunostained for Vasa, a marker specific to germ cells. Taken together, these results suggest that Nanos3 protein function is conserved between R. rugosa and mouse.
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Affiliation(s)
- Maho Kodama
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, Tokyo, Japan
| | - Madoka Yoshida
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, Tokyo, Japan
| | - Masami Endo
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, Tokyo, Japan
| | - Tohru Kobayashi
- Laboratory of Molecular Reproductive Biology, Institute for Environmental Sciences, Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, Japan
| | - Akira Oike
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, Tokyo, Japan
| | - Shigeki Yasumasu
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Masahisa Nakamura
- Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, Tokyo, Japan
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8
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Mohri KI, Nakamoto A, Shimizu T. The ontogeny of nanos homologue expression in the oligochaete annelid Tubifex tubifex. Gene Expr Patterns 2015; 20:32-41. [PMID: 26577746 DOI: 10.1016/j.gep.2015.11.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 11/04/2015] [Accepted: 11/05/2015] [Indexed: 11/17/2022]
Abstract
We have cloned and characterized the expression of a nanos homologue (designated Ttu-nos) from the oligochaete annelid Tubifex tubifex. Ttu-nos mRNA is distributed broadly throughout the early cleavage stages. Ttu-nos is expressed in most if not all of the early blastomeres, in which Ttu-nos RNA associates with pole plasms. Ttu-nos transcripts are concentrated to 2d and 4d cells. Shortly after 2d(111) (derived from 2d cell) divides into a bilateral pair of NOPQ proteloblasts, Ttu-nos RNA vanishes from the embryo, which is soon followed by the resumption of Ttu-nos expression in nascent primary blast cells produced by teloblasts. The resumption of Ttu-nos expression occurs only in a subset of teloblast lineages (viz., M, N and Q). After Ttu-nos expression is retained in the germ band for a while, it disappears in anterior-to-posterior progression. At the end of embryogenesis, there is no trace of Ttu-nos expression. Thereafter, growing juveniles do not show any sign of Ttu-nos expression, either. The first sign of Ttu-nos expression is detected in oocytes in the ovary of young adults (ca 40 days after hatching), and its expression continues in growing oocytes that undergo yolk deposition and maturation in the ovisac.
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Affiliation(s)
- Ki-Ichi Mohri
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Ayaki Nakamoto
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Takashi Shimizu
- Department of Biological Sciences, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
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9
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Stewart MJ, Stewart P, Rivera-Posada J. De novo assembly of the transcriptome ofAcanthaster plancitestes. Mol Ecol Resour 2014; 15:953-66. [DOI: 10.1111/1755-0998.12360] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2014] [Revised: 12/04/2014] [Accepted: 12/08/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Michael James Stewart
- Genecology Research Centre; Faculty of Science, Health, Education and Engineering; University of the Sunshine Coast; Maroochydore DC Queensland 4558 Australia
| | - Praphaporn Stewart
- Genecology Research Centre; Faculty of Science, Health, Education and Engineering; University of the Sunshine Coast; Maroochydore DC Queensland 4558 Australia
| | - Jairo Rivera-Posada
- ARC Centre of Excellence for Coral Reefs Studies; James Cook University; Townsville Queensland 4812 Australia
- Australian Institute of Marine Science; PMB No. 3 Townsville Queensland 4810 Australia
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10
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Pfeifer K, Schaub C, Domsch K, Dorresteijn A, Wolfstetter G. Maternal inheritance of twist and analysis of MAPK activation in embryos of the polychaete annelid Platynereis dumerilii. PLoS One 2014; 9:e96702. [PMID: 24792484 PMCID: PMC4008618 DOI: 10.1371/journal.pone.0096702] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 04/10/2014] [Indexed: 11/18/2022] Open
Abstract
In this study, we aimed to identify molecular mechanisms involved in the specification of the 4d (mesentoblast) lineage in Platynereis dumerilii. We employ RT-PCR and in situ hybridization against the Platynereis dumerilii twist homolog (Pdu-twist) to reveal mesodermal specification within this lineage. We show that Pdu-twist mRNA is already maternally distributed. After fertilization, ooplasmatic segregation leads to relocation of Pdu-twist transcripts into the somatoblast (2d) lineage and 4d, indicating that the maternal component of Pdu-twist might be an important prerequisite for further mesoderm specification but does not represent a defining characteristic of the mesentoblast. However, after the primordial germ cells have separated from the 4d lineage, zygotic transcription of Pdu-twist is exclusively observed in the myogenic progenitors, suggesting that mesodermal specification occurs after the 4d stage. Previous studies on spiral cleaving embryos revealed a spatio-temporal correlation between the 4d lineage and the activity of an embryonic organizer that is capable to induce the developmental fates of certain micromeres. This has raised the question if specification of the 4d lineage could be connected to the organizer activity. Therefore, we aimed to reveal the existence of such a proposed conserved organizer in Platynereis employing antibody staining against dpERK. In contrast to former observations in other spiralian embryos, activation of MAPK signaling during 2d and 4d formation cannot be detected which questions the existence of a conserved connection between organizer function and specification of the 4d lineage. However, our experiments unveil robust MAPK activation in the prospective nephroblasts as well as in the macromeres and some micromeres at the blastopore in gastrulating embryos. Inhibition of MAPK activation leads to larvae with a shortened body axis, defects in trunk muscle spreading and improper nervous system condensation, indicating a critical function for MAPK signaling for the reorganization of embryonic tissues during the gastrulation process.
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Affiliation(s)
- Kathrin Pfeifer
- Institut für Allgemeine und Spezielle Zoologie; Allgemeine Zoologie und Entwicklungsbiologie, Justus-Liebig-Universität Gieβen, Gieβen, Germany
| | - Christoph Schaub
- Institut für Allgemeine und Spezielle Zoologie; Allgemeine Zoologie und Entwicklungsbiologie, Justus-Liebig-Universität Gieβen, Gieβen, Germany
| | - Katrin Domsch
- Institut für Allgemeine und Spezielle Zoologie; Allgemeine Zoologie und Entwicklungsbiologie, Justus-Liebig-Universität Gieβen, Gieβen, Germany
| | - Adriaan Dorresteijn
- Institut für Allgemeine und Spezielle Zoologie; Allgemeine Zoologie und Entwicklungsbiologie, Justus-Liebig-Universität Gieβen, Gieβen, Germany
| | - Georg Wolfstetter
- Institut für Allgemeine und Spezielle Zoologie; Allgemeine Zoologie und Entwicklungsbiologie, Justus-Liebig-Universität Gieβen, Gieβen, Germany
- * E-mail:
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11
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BMP signaling is required for the generation of primordial germ cells in an insect. Proc Natl Acad Sci U S A 2014; 111:4133-8. [PMID: 24591634 DOI: 10.1073/pnas.1400525111] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Two modes of germ cell formation are known in animals. Specification through maternally inherited germ plasm occurs in many well-characterized model organisms, but most animals lack germ plasm by morphological and functional criteria. The only known alternative mechanism is induction, experimentally described only in mice, which specify germ cells through bone morphogenetic protein (BMP) signal-mediated induction of a subpopulation of mesodermal cells. Until this report, no experimental evidence of an inductive germ cell signal for specification has been available outside of vertebrates. Here we provide functional genetic experimental evidence consistent with a role for BMP signaling in germ cell formation in a basally branching insect. We show that primordial germ cells of the cricket Gryllus bimaculatus transduce BMP signals and require BMP pathway activity for their formation. Moreover, increased BMP activity leads to ectopic and supernumerary germ cells. Given the commonality of BMP signaling in mouse and cricket germ cell induction, we suggest that BMP-based germ cell formation may be a shared ancestral mechanism in animals.
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12
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Matsumoto T, Masaoka T, Fujiwara A, Nakamura Y, Satoh N, Awaji M. Reproduction-related genes in the pearl oyster genome. Zoolog Sci 2013; 30:826-50. [PMID: 24125647 DOI: 10.2108/zsj.30.826] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Molluscan reproduction has been a target of biological research because of the various reproductive strategies that have evolved in this phylum. It has also been studied for the development of fisheries technologies, particularly aquaculture. Although fundamental processes of reproduction in other phyla, such as vertebrates and arthropods, have been well studied, information on the molecular mechanisms of molluscan reproduction remains limited. The recently released draft genome of the pearl oyster Pinctada fucata provides a novel and powerful platform for obtaining structural information on the genes and proteins involved in bivalve reproduction. In the present study, we analyzed the pearl oyster draft genome to screen reproduction-related genes. Analysis was mainly conducted for genes reported from other molluscs for encoding orthologs of reproduction-related proteins in other phyla. The gene search in the P. fucata gene models (version 1.1) and genome assembly (version 1.0) were performed using Genome Browser and BLAST software. The obtained gene models were then BLASTP searched against a public database to confirm the best-hit sequences. As a result, more than 40 gene models were identified with high accuracy to encode reproduction-related genes reported for P. fucata and other molluscs. These include vasa, nanos, doublesex- and mab-3-related transcription factor, 5-hydroxytryptamine (5-HT) receptors, vitellogenin, estrogen receptor, and others. The set of reproduction-related genes of P. fucata identified in the present study constitute a new tool for research on bivalve reproduction at the molecular level.
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Affiliation(s)
- Toshie Matsumoto
- 1 Aquaculture Technology Division, National Research Institute of Aquaculture, Fisheries Research Agency, Minami-lse, Watarai, Mie 516-0193, Japan
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13
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Cho SJ, Vallès Y, Weisblat DA. Differential expression of conserved germ line markers and delayed segregation of male and female primordial germ cells in a hermaphrodite, the leech helobdella. Mol Biol Evol 2013; 31:341-54. [PMID: 24217283 PMCID: PMC3907050 DOI: 10.1093/molbev/mst201] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
In sexually reproducing animals, primordial germ cells (PGCs) are often set aside early in embryogenesis, a strategy that minimizes the risk of genomic damage associated with replication and mitosis during the cell cycle. Here, we have used germ line markers (piwi, vasa, and nanos) and microinjected cell lineage tracers to show that PGC specification in the leech genus Helobdella follows a different scenario: in this hermaphrodite, the male and female PGCs segregate from somatic lineages only after more than 20 rounds of zygotic mitosis; the male and female PGCs share the same (mesodermal) cell lineage for 19 rounds of zygotic mitosis. Moreover, while all three markers are expressed in both male and female reproductive tissues of the adult, they are expressed differentially between the male and female PGCs of the developing embryo: piwi and vasa are expressed preferentially in female PGCs at a time when nanos is expressed preferentially in male PGCs. A priori, the delayed segregation of male and female PGCs from somatic tissues and from one another increases the probability of mutations affecting both male and female PGCs of a given individual. We speculate that this suite of features, combined with a capacity for self-fertilization, may contribute to the dramatically rearranged genome of Helobdella robusta relative to other animals.
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Affiliation(s)
- Sung-Jin Cho
- Department of Molecular and Cell Biology, LSA, University of California, Berkeley
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14
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Ewen-Campen B, Donoughe S, Clarke DN, Extavour CG. Germ cell specification requires zygotic mechanisms rather than germ plasm in a basally branching insect. Curr Biol 2013; 23:835-42. [PMID: 23623552 DOI: 10.1016/j.cub.2013.03.063] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 03/03/2013] [Accepted: 03/22/2013] [Indexed: 12/25/2022]
Abstract
BACKGROUND Primordial germ cell (PGC) specification is a universal process across animals, but the molecular mechanisms specifying PGCs are remarkably diverse. In Drosophila, PGCs are specified by maternally provided, asymmetrically localized cytoplasmic factors (germ plasm). In contrast, historical literature on most other arthropods reports that PGCs arise from mesoderm during midembryogenesis, suggesting that an arthropod last common ancestor may have specified PGCs via zygotic mechanisms. However, there has been no direct experimental evidence to date for germ plasm-independent arthropod PGC specification. RESULTS Here we show that in a basally branching insect, the cricket Gryllus bimaculatus, conserved germ plasm molecules are ubiquitously, rather than asymmetrically, localized during oogenesis and early embryogenesis. Molecular and cytological analyses suggest that Gryllus PGCs arise from abdominal mesoderm during segmentation, and twist RNAi embryos that lack mesoderm fail to form PGCs. Using RNA interference we show that vasa and piwi are not required maternally or zygotically for PGC formation but rather are required for primary spermatogonial divisions in adult males. CONCLUSIONS These observations suggest that Gryllus lacks a maternally inherited germ plasm, in contrast with many holometabolous insects, including Drosophila. The mesodermal origin of Gryllus PGCs and absence of instructive roles for vasa and piwi in PGC formation are reminiscent of mouse PGC specification and suggest that zygotic cell signaling may direct PGC specification in Gryllus and other Hemimetabola.
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Affiliation(s)
- Ben Ewen-Campen
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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15
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Abstract
Annelids (the segmented worms) have a long history in studies of animal developmental biology, particularly with regards to their cleavage patterns during early development and their neurobiology. With the relatively recent reorganisation of the phylogeny of the animal kingdom, and the distinction of the super-phyla Ecdysozoa and Lophotrochozoa, an extra stimulus for studying this phylum has arisen. As one of the major phyla within Lophotrochozoa, Annelida are playing an important role in deducing the developmental biology of the last common ancestor of the protostomes and deuterostomes, an animal from which >98% of all described animal species evolved.
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Affiliation(s)
- David E. K. Ferrier
- The Scottish Oceans Institute, the Gatty Marine Laboratory, University of St Andrews, East Sands, St Andrews, Fife, KY16 8LB, UK
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16
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Maternally localized germ plasm mRNAs and germ cell/stem cell formation in the cnidarian Clytia. Dev Biol 2012; 364:236-48. [DOI: 10.1016/j.ydbio.2012.01.018] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 01/11/2012] [Accepted: 01/20/2012] [Indexed: 01/07/2023]
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17
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Abstract
The germline of multicellular animals is segregated from somatic tissues, which is an essential developmental process for the next generation. Although certain ecdysozoans and chordates segregate their germline during embryogenesis, animals from other taxa segregate their germline after embryogenesis from multipotent progenitor cells. An overlapping set of genes, including vasa, nanos and piwi, operate in both multipotent precursors and in the germline. As we propose here, this conservation implies the existence of an underlying germline multipotency program in these cell types that has a previously underappreciated and conserved function in maintaining multipotency.
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Affiliation(s)
- Celina E. Juliano
- Department of Molecular and Cellular Biology, Brown University, Providence, RI 02912, USA
| | - S. Zachary Swartz
- Department of Molecular and Cellular Biology, Brown University, Providence, RI 02912, USA
| | - Gary M. Wessel
- Department of Molecular and Cellular Biology, Brown University, Providence, RI 02912, USA
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Kranz AM, Tollenaere A, Norris BJ, Degnan BM, Degnan SM. Identifying the germline in an equally cleaving mollusc: Vasa and Nanos expression during embryonic and larval development of the vetigastropod Haliotis asinina. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2010; 314:267-79. [PMID: 20095031 DOI: 10.1002/jez.b.21336] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Members of the Vasa and Nanos gene families are important for the specification and development of the germline in diverse animals. Here, we determine spatial and temporal expression of Vasa and Nanos to investigate germline development in the vetigastropod Haliotis asinina. This is the first time these genes have been examined in an equally cleaving lophotrochozoan species. We find that HasVasa and HasNanos have largely overlapping, but not identical, expression patterns during embryonic and larval development, with both being maternally expressed and localized to the micromere cell lineages during cleavage. As embryonic development continues, HasVasa and HasNanos become progressively more enriched in the dorsal quadrant of the embryo. By the trochophore stage, both HasVasa and HasNanos are expressed in the putative mesodermal bands of the larva. This differs from the unequally cleaving gastropod Illyanasa obsoleta, in which IoVasa and IoNanos expression is detectable only in the early embryo and not during gastrulation and larval development. Our results suggest that the H. asinina germline arises from the 4d cell lineage and that primordial germ cells (PGCs) are not specified exclusively by maternally inherited determinants (preformation). As such, we infer that inductive signals (epigenesis) play an important role in specifying PGCs in H. asinina. We hypothesize that HasVasa is expressed in a population of undifferentiated multipotent cells, from which the PGCs are segregated later during development.
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Affiliation(s)
- Alexandrea M Kranz
- The University of Queensland, School of Biological Sciences, Brisbane, Queensland, Australia
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Abstract
At least five animal phyla exhibit spiralian development, which is characterized by striking similarities in the geometry of the early cleavage pattern and the fate map of the blastula, along with similarities in larval morphology. Recent advances in reconstructing the phylogeny of spiralians and their relatives suggest that the common ancestor of a large clade of protostome phyla known as the Lophotrochozoa had spiralian development. In this minireview, I describe characteristics of spiralian development and some recent insights into its mechanisms and evolution.
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Affiliation(s)
- J David Lambert
- Department of Biology, University of Rochester, Rochester, NY 14607, USA.
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Zhang SO, Kuo DH, Weisblat DA. Grandparental stem cells in leech segmentation: differences in CDC42 expression are correlated with an alternating pattern of blast cell fates. Dev Biol 2009; 336:112-21. [PMID: 19747476 PMCID: PMC2783548 DOI: 10.1016/j.ydbio.2009.09.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Revised: 08/27/2009] [Accepted: 09/03/2009] [Indexed: 11/30/2022]
Abstract
Embryonic segmentation in clitellate annelids (oligochaetes and leeches) is a cell lineage-driven process. Embryos of these worms generate a posterior growth zone consisting of 5 bilateral pairs of identified segmentation stem cells (teloblasts), each of which produces a column of segmental founder cells (blast cells). Each blast cell generates a lineage-specific clone via a stereotyped sequence of cell divisions, which are typically unequal both in terms of the relative size of the sister cells and in the progeny to which they give rise. In two of the five teloblast lineages, including the ventralmost, primary neurogenic (N) lineage, the blast cells adopt two different fates, designated nf and ns, in exact alternation within the blast cell column; this is termed a grandparental stem cell lineage. To lay groundwork for investigating unequal divisions in the leech Helobdella, we have surveyed the Helobdella robusta genome for genes encoding orthologs of the Rho family GTPases, including the rho, rac and cdc42 sub-families, which are known to be involved in multiple processes involving cell polarization in other systems. We find that, in contrast to most other known systems the Helobdella genome contains two cdc42 orthologs, one of which is expressed at higher levels in the ns blast cells than in nf blast cells. We also demonstrate that the asymmetric divisions of the primary nf and ns blast cells are regulated by the polarized distribution of the activated form of the Cdc42 protein, rather than by the overall level of expression. Our results provide the first molecular insights into the mechanisms of the grandparental stem cell lineages, a novel, yet evolutionarily ancient stem cell division pattern. Our results also provide an example in which asymmetries in the distribution of Cdc42 activity, rather than in the overall levels of Cdc42 protein, are important regulating unequal divisions in animal cells.
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Affiliation(s)
- Shaobing O Zhang
- Graduate Group in Biophysics, University of California, Berkeley, CA, USA
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Rivera AS, Weisblat DA. And Lophotrochozoa makes three: Notch/Hes signaling in annelid segmentation. Dev Genes Evol 2008; 219:37-43. [PMID: 19011897 DOI: 10.1007/s00427-008-0264-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Accepted: 10/16/2008] [Indexed: 11/29/2022]
Abstract
Segmentation is unquestionably a major factor in the evolution of complex body plans, but how this trait itself evolved is unknown. Approaching this problem requires comparing the molecular mechanisms of segmentation in diverse segmented and unsegmented taxa. Notch/Hes signaling is involved in segmentation in sequentially segmenting vertebrates and arthropods, as judged by patterns of expression of one or more genes in this network and by the disruption of segmental patterning when Notch/Hes signaling is disrupted. We have previously shown that Notch and Hes homologs are expressed in the posterior progress zone (PPZ), from which segments arise, in the leech Helobdella robusta, a sequentially segmenting lophotrochozoan (phylum Annelida). Here, we show that disrupting Notch/Hes signaling disrupts segmentation in this species as well. Thus, Notch/Hes functions in either the maintenance of the PPZ and/or the patterning processes of segmentation in representatives of all three superphyla of bilaterally symmetric animals. These results are consistent with two evolutionary scenarios. In one, segmentation was already present in the ancestor of all three superphyla. In the other, Notch/Hes signaling functioned in axial growth by terminal addition in an unsegmented bilaterian ancestor, and was subsequently exapted to function in segmentation as that process evolved independently in two or more taxa.
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Affiliation(s)
- Ajna S Rivera
- Deparment of MCB, University of California, Berkeley, CA 94720, USA.
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Nanos Is Required in Somatic Blast Cell Lineages in the Posterior of a Mollusk Embryo. Curr Biol 2008; 18:331-6. [DOI: 10.1016/j.cub.2008.01.055] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 01/17/2008] [Accepted: 01/21/2008] [Indexed: 11/20/2022]
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Abstract
Asymmetric cell divisions are a crucial mode of cell fate specification in multicellular organisms, but their relative contribution to early embryonic patterning varies among taxa. In the embryo of the mollusc Ilyanassa, most of the early cell divisions are overtly asymmetric. During Ilyanassa early cleavage, mRNAs for several conserved developmental patterning genes localize to interphase centrosomes, and then during division they move to a portion of the cortex that will be inherited by one daughter cell. Here we report an unbiased survey of RNA localization in the Ilyanassa embryo, and examine the overall patterns of centrosomal localization during early development. We find that 3-4% of RNAs are specifically localized to centrosomes during early development, and the remainder are either ubiquitously distributed throughout the cytoplasm or weakly enriched on centrosomes compared with levels in the cytoplasm. We observe centrosomal localization of RNAs in all cells from zygote through the fifth cleavage cycle, and asymmetric RNA segregation in all divisions after the four-cell stage. Remarkably, each specifically localized message is found on centrosomes in a unique subset of cells during early cleavages, and most are found in unique sets of cells at the 24-cell stage. Several specifically localized RNAs are homologous to developmental regulatory proteins in other embryos. These results demonstrate that the mechanisms of localization and segregation are extraordinarily intricate in this system, and suggest that these events are involved in cell fate specification across all lineages in the early Ilyanassa embryo. We propose that greater reliance on segregation of determinants in early cleavage increases constraint on cleavage patterns in molluscs and other spiralian groups.
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Affiliation(s)
- Evan P Kingsley
- Department of Biology, University of Rochester, Rochester, NY 14627, USA
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