1
|
Elagoz AM, Van Dijck M, Lassnig M, Seuntjens E. Embryonic development of a centralised brain in coleoid cephalopods. Neural Dev 2024; 19:8. [PMID: 38907272 PMCID: PMC11191162 DOI: 10.1186/s13064-024-00186-2] [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] [Received: 02/01/2024] [Accepted: 06/12/2024] [Indexed: 06/23/2024] Open
Abstract
The last common ancestor of cephalopods and vertebrates lived about 580 million years ago, yet coleoid cephalopods, comprising squid, cuttlefish and octopus, have evolved an extraordinary behavioural repertoire that includes learned behaviour and tool utilization. These animals also developed innovative advanced defence mechanisms such as camouflage and ink release. They have evolved unique life cycles and possess the largest invertebrate nervous systems. Thus, studying coleoid cephalopods provides a unique opportunity to gain insights into the evolution and development of large centralised nervous systems. As non-model species, molecular and genetic tools are still limited. However, significant insights have already been gained to deconvolve embryonic brain development. Even though coleoid cephalopods possess a typical molluscan circumesophageal bauplan for their central nervous system, aspects of its development are reminiscent of processes observed in vertebrates as well, such as long-distance neuronal migration. This review provides an overview of embryonic coleoid cephalopod research focusing on the cellular and molecular aspects of neurogenesis, migration and patterning. Additionally, we summarize recent work on neural cell type diversity in embryonic and hatchling cephalopod brains. We conclude by highlighting gaps in our knowledge and routes for future research.
Collapse
Affiliation(s)
- Ali M Elagoz
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium.
| | - Marie Van Dijck
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium
| | - Mark Lassnig
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium
| | - Eve Seuntjens
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium.
- Leuven Brain Institute, KU Leuven, Leuven, Belgium.
- Leuven Institute for Single Cell Omics, KU Leuven, Leuven, Belgium.
| |
Collapse
|
2
|
Styfhals R, Zolotarov G, Hulselmans G, Spanier KI, Poovathingal S, Elagoz AM, De Winter S, Deryckere A, Rajewsky N, Ponte G, Fiorito G, Aerts S, Seuntjens E. Cell type diversity in a developing octopus brain. Nat Commun 2022; 13:7392. [PMID: 36450803 PMCID: PMC9712504 DOI: 10.1038/s41467-022-35198-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 11/22/2022] [Indexed: 12/02/2022] Open
Abstract
Octopuses are mollusks that have evolved intricate neural systems comparable with vertebrates in terms of cell number, complexity and size. The brain cell types that control their sophisticated behavioral repertoire are still unknown. Here, we profile the cell diversity of the paralarval Octopus vulgaris brain to build a cell type atlas that comprises mostly neural cells, but also multiple glial subtypes, endothelial cells and fibroblasts. We spatially map cell types to the vertical, subesophageal and optic lobes. Investigation of cell type conservation reveals a shared gene signature between glial cells of mouse, fly and octopus. Genes related to learning and memory are enriched in vertical lobe cells, which show molecular similarities with Kenyon cells in Drosophila. We construct a cell type taxonomy revealing transcriptionally related cell types, which tend to appear in the same brain region. Together, our data sheds light on cell type diversity and evolution in the octopus brain.
Collapse
Affiliation(s)
- Ruth Styfhals
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Naples, Italy
| | - Grygoriy Zolotarov
- Laboratory for Systems Biology of Gene Regulatory Elements, Berlin Institute for Systems Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Hannoversche Str. 28, 10115, Berlin, Germany
| | - Gert Hulselmans
- Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
- VIB Center for Brain & Disease Research, KU Leuven, Leuven, 3000, Belgium
| | - Katina I Spanier
- Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
- VIB Center for Brain & Disease Research, KU Leuven, Leuven, 3000, Belgium
| | | | - Ali M Elagoz
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium
| | - Seppe De Winter
- Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
- VIB Center for Brain & Disease Research, KU Leuven, Leuven, 3000, Belgium
| | - Astrid Deryckere
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium
- Department of Biological Sciences, Columbia University, New York, US
| | - Nikolaus Rajewsky
- Laboratory for Systems Biology of Gene Regulatory Elements, Berlin Institute for Systems Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Hannoversche Str. 28, 10115, Berlin, Germany
- Department of Pediatric Oncology/Hematology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Giovanna Ponte
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Naples, Italy
| | - Graziano Fiorito
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Naples, Italy
| | - Stein Aerts
- Department of Human Genetics, KU Leuven, Leuven, 3000, Belgium
- VIB Center for Brain & Disease Research, KU Leuven, Leuven, 3000, Belgium
| | - Eve Seuntjens
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven, Belgium.
| |
Collapse
|
3
|
Jékely G. The chemical brain hypothesis for the origin of nervous systems. Philos Trans R Soc Lond B Biol Sci 2021; 376:20190761. [PMID: 33550946 PMCID: PMC7935135 DOI: 10.1098/rstb.2019.0761] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2020] [Indexed: 12/13/2022] Open
Abstract
In nervous systems, there are two main modes of transmission for the propagation of activity between cells. Synaptic transmission relies on close contact at chemical or electrical synapses while volume transmission is mediated by diffusible chemical signals and does not require direct contact. It is possible to wire complex neuronal networks by both chemical and synaptic transmission. Both types of networks are ubiquitous in nervous systems, leading to the question which of the two appeared first in evolution. This paper explores a scenario where chemically organized cellular networks appeared before synapses in evolution, a possibility supported by the presence of complex peptidergic signalling in all animals except sponges. Small peptides are ideally suited to link up cells into chemical networks. They have unlimited diversity, high diffusivity and high copy numbers derived from repetitive precursors. But chemical signalling is diffusion limited and becomes inefficient in larger bodies. To overcome this, peptidergic cells may have developed projections and formed synaptically connected networks tiling body surfaces and displaying synchronized activity with pulsatile peptide release. The advent of circulatory systems and neurohemal organs further reduced the constraint imposed on chemical signalling by diffusion. This could have contributed to the explosive radiation of peptidergic signalling systems in stem bilaterians. Neurosecretory centres in extant nervous systems are still predominantly chemically wired and coexist with the synaptic brain. This article is part of the theme issue 'Basal cognition: multicellularity, neurons and the cognitive lens'.
Collapse
Affiliation(s)
- Gáspár Jékely
- Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| |
Collapse
|
4
|
Methods in Brain Development of Molluscs. Methods Mol Biol 2019. [PMID: 31552662 DOI: 10.1007/978-1-4939-9732-9_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Representatives of the phylum Mollusca have long been important models in neurobiological research. Recently, the routine application of immunocytochemistry and gene expression analyses in combination with confocal laserscanning microscopy has allowed fast generation of highly detailed reconstructions of neural structures of even the smallest multicellular animals, including early developmental stages. As a consequence, large-scale comparative analyses of neurogenesis-an important prerequisite for inferences concerning the evolution of animal nervous systems-are now possible in a reasonable amount of time. Herein, we describe immunocytochemical staining and in situ hybridization protocols for both, whole-mount preparations of developmental stages-usually 70-300 μm in size-as well as for vibratome and cryostat sections of complex brains. Although our procedures have been optimized for marine molluscs, they may easily be adapted to other (marine) organisms by the creative neurobiologist.
Collapse
|
6
|
Wollesen T, McDougall C, Degnan BM, Wanninger A. POU genes are expressed during the formation of individual ganglia of the cephalopod central nervous system. EvoDevo 2014; 5:41. [PMID: 25908957 PMCID: PMC4407788 DOI: 10.1186/2041-9139-5-41] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 09/29/2014] [Indexed: 11/18/2022] Open
Abstract
Background Among the Lophotrochozoa, cephalopods possess the highest degree of central nervous system (CNS) centralization and complexity. Although the anatomy of the developing cephalopod CNS has been investigated, the developmental mechanisms underlying brain development and evolution are unknown. POU genes encode key transcription factors controlling nervous system development in a range of bilaterian species, including lophotrochozoans. In this study, we investigate the expression of POU genes during early development of the pygmy squid Idiosepius notoides and make comparisons with other bilaterians to reveal whether these genes have conserved or divergent roles during CNS development in this species. Results POU2, POU3, POU4 and POU6 orthologs were identified in transcriptomes derived from developmental stages and adult brain tissue of I. notoides. All four POU gene orthologs are expressed in different spatiotemporal combinations in the early embryo. Ino-POU2 is expressed in the gills and the palliovisceral, pedal, and optic ganglia of stage 19 to 20 embryos, whereas the cerebral and palliovisceral ganglia express Ino-POU3. Ino-POU4 is expressed in the optic and palliovisceral ganglia and the arms/intrabrachial ganglia of stage 19 to 20 individuals. Ino-POU6 is expressed in the palliovisceral ganglia during early development. In stage 25 embryos expression domains include the intrabrachial ganglia (Ino-POU3) and the pedal ganglia (Ino-POU6). All four POU genes are strongly expressed in large areas of the brain of stage 24 to 26 individuals. Expression could not be detected in late prehatching embryos (approximately stage 27 to 30). Conclusions The expression of four POU genes in unique spatiotemporal combinations during early neurogenesis and sensory organ development of I. notoides suggests that they fulfill distinct tasks during early brain development. Comparisons with other bilaterian species reveal that POU gene expression is associated with anteriormost neural structures, even between animals for which these structures are unlikely to be homologous. Within lophotrochozoans, POU3 and POU4 are the only two genes that have been comparatively investigated. Their expression patterns are broadly similar, indicating that the increased complexity of the cephalopod brain is likely due to other unknown factors.
Collapse
Affiliation(s)
- Tim Wollesen
- Department of Integrative Zoology, Faculty of Sciences, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
| | - Carmel McDougall
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072 Australia
| | - Bernard M Degnan
- School of Biological Sciences, The University of Queensland, Brisbane, QLD 4072 Australia
| | - Andreas Wanninger
- Department of Integrative Zoology, Faculty of Sciences, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
| |
Collapse
|
7
|
Wanninger A, Wollesen T. Methods in brain development of molluscs. Methods Mol Biol 2014; 1082:117-125. [PMID: 24048930 DOI: 10.1007/978-1-62703-655-9_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Representatives of the phylum Mollusca have long been important models in neurobiological research. Recently, the routine application of immunocytochemistry in combination with confocal laser scanning microscopy has allowed fast generation of highly detailed reconstructions of neural structures of even the smallest multicellular animals, including early developmental stages. As a consequence, large-scale comparative analyses of neurogenesis-an important prerequisite for inferences concerning the evolution of animal nervous systems-are now possible in a reasonable amount of time. Herein, we describe immunocytochemical staining protocols for both whole-mount preparations of developmental stages-usually 70-300 μm in size-as well as for vibratome sections of complex brains. Although our procedures have been optimized for marine molluscs, they may easily be adapted for other (marine) organisms by the creative neurobiologist.
Collapse
Affiliation(s)
- Andreas Wanninger
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Vienna, Austria
| | | |
Collapse
|
8
|
Hindinger S, Schwaha T, Wanninger A. Immunocytochemical studies reveal novel neural structures in nemertean pilidium larvae and provide evidence for incorporation of larval components into the juvenile nervous system. Front Zool 2013; 10:31. [PMID: 23701905 PMCID: PMC3670813 DOI: 10.1186/1742-9994-10-31] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 05/13/2013] [Indexed: 11/30/2022] Open
Abstract
Introduction Nemertea is one of the least studied lophotrochozoan phyla concerning neurogenesis. The sparse data available do not unambiguously allow for answering questions with respect to the neural groundplan of the phylum or the fate of larval neural structures during metamorphosis. In order to contribute to this issue, we studied neurotransmitter distribution during development of the pilidiophoran Lineus albocinctus Verrill, 1900. Results Two serotonin-like immunoreactive (lir) neurons are present in the anterior part of the apical plate. They send numerous processes into the four lobes of the pilidium larva, where they form a complex subepithelial nerve net. All four larval lobes are underlain by a marginal neurite bundle, which is associated with numerous serotonin-lir monociliated perikarya. A serotonin-lir oral nerve ring encircles the stomach sphincter and is associated with few serotonin-lir conical cells. Two suboral neurites descend from the oral nerve ring and merge with the marginal neurite bundle. The oral nerve ring and the suboral neurites contain the mollusk-specific VD1/RPD2 α-neuropeptide. The lateral lobes of the larva have three and the anterior and the posterior lobes two VD1/RPD2-lir marginal neurite bundles. The lobar FMRFamide-lir plexus of Lineus albocinctus is much more complex than previously described for any pilidium larva. It includes a circumesophageal neurite that descends along each side of the larval esophagus and together with the inner marginal neurite bundle gives rise to the lobar plexus of the lateral lobes. An outer FMRFamide-lir marginal neurite bundle with numerous associated FMRFamide-lir marginal sensory cells surrounds all four lobes. FMRFamide-lir structures are absent in the larval apical region. The oral nerve ring and the two suboral serotonin-lir neurites are incorporated into the juvenile nervous system. Conclusion Our study confirms the presence of serotonin-lir components in the apical region of the pilidium larva of Lineus albocinctus and thus contradicts an earlier study on the same species. We show that the nervous system of pilidium larvae, especially the FMRFamide-lir components, is much more complex than previously assumed. The presence of the VD1/RPD2-α-neuropeptide indicates that this compound may have been part of the lophotrochozoan neural groundplan.
Collapse
Affiliation(s)
- Sabine Hindinger
- Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Althanstr, 14, Vienna, 1090, Austria.
| | | | | |
Collapse
|