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Schiffer PH, Kroiher M, Kraus C, Koutsovoulos GD, Kumar S, R Camps JI, Nsah NA, Stappert D, Morris K, Heger P, Altmüller J, Frommolt P, Nürnberg P, Thomas WK, Blaxter ML, Schierenberg E. The genome of Romanomermis culicivorax: revealing fundamental changes in the core developmental genetic toolkit in Nematoda. BMC Genomics 2013; 14:923. [PMID: 24373391 PMCID: PMC3890508 DOI: 10.1186/1471-2164-14-923] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 12/17/2013] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND The genetics of development in the nematode Caenorhabditis elegans has been described in exquisite detail. The phylum Nematoda has two classes: Chromadorea (which includes C. elegans) and the Enoplea. While the development of many chromadorean species resembles closely that of C. elegans, enoplean nematodes show markedly different patterns of early cell division and cell fate assignment. Embryogenesis of the enoplean Romanomermis culicivorax has been studied in detail, but the genetic circuitry underpinning development in this species has not been explored. RESULTS We generated a draft genome for R. culicivorax and compared its gene content with that of C. elegans, a second enoplean, the vertebrate parasite Trichinella spiralis, and a representative arthropod, Tribolium castaneum. This comparison revealed that R. culicivorax has retained components of the conserved ecdysozoan developmental gene toolkit lost in C. elegans. T. spiralis has independently lost even more of this toolkit than has C. elegans. However, the C. elegans toolkit is not simply depauperate, as many novel genes essential for embryogenesis in C. elegans are not found in, or have only extremely divergent homologues in R. culicivorax and T. spiralis. Our data imply fundamental differences in the genetic programmes not only for early cell specification but also others such as vulva formation and sex determination. CONCLUSIONS Despite the apparent morphological conservatism, major differences in the molecular logic of development have evolved within the phylum Nematoda. R. culicivorax serves as a tractable system to contrast C. elegans and understand how divergent genomic and thus regulatory backgrounds nevertheless generate a conserved phenotype. The R. culicivorax draft genome will promote use of this species as a research model.
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Affiliation(s)
| | - Michael Kroiher
- Zoologisches Institut, Universität zu Köln, Cologne, NRW, Germany
| | | | - Georgios D Koutsovoulos
- Institute of Evolutionary Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, Scotland, UK
| | - Sujai Kumar
- Institute of Evolutionary Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, Scotland, UK
| | - Julia I R Camps
- Zoologisches Institut, Universität zu Köln, Cologne, NRW, Germany
| | - Ndifon A Nsah
- Zoologisches Institut, Universität zu Köln, Cologne, NRW, Germany
| | - Dominik Stappert
- Institute für Entwicklungsbiologie, Universität zu Köln, Cologne, NRW, Germany
| | - Krystalynne Morris
- Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH, USA
| | - Peter Heger
- Zoologisches Institut, Universität zu Köln, Cologne, NRW, Germany
| | - Janine Altmüller
- Cologne Center for Genomics, Universität zu Köln, Cologne, NRW, Germany
| | - Peter Frommolt
- Cologne Center for Genomics, Universität zu Köln, Cologne, NRW, Germany
| | - Peter Nürnberg
- Cologne Center for Genomics, Universität zu Köln, Cologne, NRW, Germany
| | - W Kelley Thomas
- Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH, USA
| | - Mark L Blaxter
- Institute of Evolutionary Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, Scotland, UK
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Abstract
Early cleavages of the marine nematode Enoplus brevis are symmetrical and occur in synchrony. At the 2- to 16-cell stages, blastomeres are indistinguishable. The progeny of blastomeres was investigated by intracellular injections of fluorescent dyes and horse radish peroxidase. One blastomere of the 2-cell embryo gives rise to a compact group of cells occupying about half of an embryo. The border between labeled and unlabeled cells differs in each embryo dividing it to anterior-posterior, left-right or intermediate parts. At the 8-cell stage, one blastomere gives rise to only endoderm, whereas the other blastomeres produce progeny that form multiple cell types, including nerve, muscle and hypoderm cells, in various proportions. Thus the fates of the blastomeres of early E. brevis embryos, with the exception of the endoderm precursor, are not determined. The process of gastrulation in E. brevis is very similar to that in Caenorhabditis elegans and other nematodes. At the beginning of gastrulation, the 2-celled endoderm precursor lies on the surface of embryo and then sinks inwards. After labeling of cells on the ventral side (near endoderm precursor) at the beginning of gastrulation, their progeny differentiate predominantly into body muscles or pharyngeal cells of the first stage larva. Cells that are located more laterally give rise mainly to neurons. The dorsal blastomeres differentiated principally into hypoderm cells. Our study suggests that a precise cell lineage is not a necessary attribute of nematode development.
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Affiliation(s)
- D A Voronov
- Institute of Problems of Information Transmission, Russian Academy of Sciences, Moscow.
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