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Marianne E. Bronner - One of the best experts on this subject based on the ideXlab platform.
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Hmx gene conservation identifies the Evolutionary Origin of vertebrate cranial ganglia
2020Co-Authors: Vasileios Papdogiannis, Marianne E. Bronner, Hugo J. Parker, Alessandro Pennati, Cedric Patthey, Sebastian M. ShimeldAbstract:The Evolutionary Origin of vertebrates included innovations in sensory processing associated with the acquisition of a predatory lifestyle. Vertebrates perceive external stimuli through sensory systems serviced by cranial sensory ganglia (CSG) which develop from cranial placodes; however understanding the Evolutionary Origin of placodes and CSGs is hampered by the gulf between living lineages and difficulty in assigning homology between cell types and structures. Here we use the Hmx gene family to address this question. We show Hmx is a constitutive component of vertebrate CSG development and that Hmx in the tunicate Ciona is able to drive the differentiation program of Bipolar Tail Neurons (BTNs), cells previously thought neural crest homologs. Using Ciona and lamprey transgenesis we demonstrate that a unique, tandemly duplicated enhancer pair regulated Hmx in the stem-vertebrate lineage. Strikingly, we also show robust vertebrate Hmx enhancer function in Ciona, demonstrating that deep conservation of the upstream regulatory network spans the Evolutionary Origin of vertebrates. These experiments demonstrate regulatory and functional conservation between Ciona and vertebrate Hmx, and confirm BTNs as CSG homologs. Our analysis also identifies derived Evolutionary changes, including a genetic basis for secondary simplicity in Ciona and unique regulatory complexity in vertebrates.
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Ancient Evolutionary Origin of vertebrate enteric neurons from trunk-derived neural crest
Nature, 2017Co-Authors: Stephen A. Green, Marianne E. BronnerAbstract:In gnathostomes (jawed vertebrates), the ganglia of the enteric nervous system are populated from the vagal neural crest, which invades the gut at the anterior end and makes its way to the back. In mammals, however, Schwann cell precursors also contribute to these ganglia. This second mechanism might in fact be a relic of ancient times rather than a mammalian innovation. Here, Marianne Bronner and colleagues show that the vagal neural crest plays no part in the population of the enteric nervous system in a jawless vertebrate, the sea lamprey, in which the whole gut is populated by Schwann-cell-precursor-like cells from the trunk neural crest. The enteric nervous system of jawed vertebrates arises primarily from vagal neural crest cells that migrate to the foregut and subsequently colonize and innervate the entire gastrointestinal tract. Here we examine development of the enteric nervous system in the basal jawless vertebrate the sea lamprey ( Petromyzon marinus ) to gain insight into its Evolutionary Origin. Surprisingly, we find no evidence for the existence of a vagally derived enteric neural crest population in the lamprey. Rather, labelling with the lipophilic dye DiI shows that late-migrating cells, Originating from the trunk neural tube and associated with nerve fibres, differentiate into neurons within the gut wall and typhlosole. We propose that these trunk-derived neural crest cells may be homologous to Schwann cell precursors, recently shown in mammalian embryos to populate post-embryonic parasympathetic ganglia^ 1 , 2 , including enteric ganglia^ 3 . Our results suggest that neural-crest-derived Schwann cell precursors made an important contribution to the ancient enteric nervous system of early jawless vertebrates, a role that was largely subsumed by vagal neural crest cells in early gnathostomes. Whereas the enteric nervous system of jawed vertebrates is derived largely from the vagal neural crest, that of the sea lamprey ( Petromyzon marinus ) is populated by trunk-derived neural crest cells that may be homologous to Schwann cell precursors.
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Ancient Evolutionary Origin of vertebrate enteric neurons from trunk-derived neural crest.
Nature, 2017Co-Authors: Stephen A. Green, Marianne E. BronnerAbstract:The enteric nervous system of jawed vertebrates arises primarily from vagal neural crest cells that migrate to the foregut and subsequently colonize and innervate the entire gastrointestinal tract. Here we examine development of the enteric nervous system in the basal jawless vertebrate the sea lamprey (Petromyzon marinus) to gain insight into its Evolutionary Origin. Surprisingly, we find no evidence for the existence of a vagally derived enteric neural crest population in the lamprey. Rather, labelling with the lipophilic dye DiI shows that late-migrating cells, Originating from the trunk neural tube and associated with nerve fibres, differentiate into neurons within the gut wall and typhlosole. We propose that these trunk-derived neural crest cells may be homologous to Schwann cell precursors, recently shown in mammalian embryos to populate post-embryonic parasympathetic ganglia, including enteric ganglia. Our results suggest that neural-crest-derived Schwann cell precursors made an important contribution to the ancient enteric nervous system of early jawless vertebrates, a role that was largely subsumed by vagal neural crest cells in early gnathostomes.
Tyler R. Lyson - One of the best experts on this subject based on the ideXlab platform.
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Evolutionary Origin of the turtle skull
Nature, 2015Co-Authors: Gaberiel Bever, Tyler R. Lyson, Daniel J Field, Bhart-anjan S. BhullarAbstract:Computed tomography and phylogenetic analysis of the Eunotosaurus africanus skull suggests that not only is Eunotosaurus an early relative of the group that eventually evolved into turtles, but that it is also a diapsid caught in the act of evolving towards a secondarily anapsid state. Transitional fossils informing the Origin of turtles are among the most sought-after discoveries in palaeontology^ 1 , 2 , 3 , 4 , 5 . Despite strong genomic evidence indicating that turtles evolved from within the diapsid radiation (which includes all other living reptiles^ 6 , 7 ), evidence of the inferred transformation between an ancestral turtle with an open, diapsid skull to the closed, anapsid condition of modern turtles remains elusive. Here we use high-resolution computed tomography and a novel character/taxon matrix to study the skull of Eunotosaurus africanus , a 260-million-year-old fossil reptile from the Karoo Basin of South Africa, whose distinctive postcranial skeleton shares many unique features with the shelled body plan of turtles^ 2 , 3 , 4 . Scepticism regarding the status of Eunotosaurus as the earliest stem turtle arises from the possibility that these shell-related features are the products of Evolutionary convergence. Our phylogenetic analyses indicate strong cranial support for Eunotosaurus as a critical transitional form in turtle evolution, thus fortifying a 40-million-year extension to the turtle stem and moving the ecological context of its Origin back onto land^ 8 , 9 . Furthermore, we find unexpected evidence that Eunotosaurus is a diapsid reptile in the process of becoming secondarily anapsid. This is important because categorizing the skull based on the number of openings in the complex of dermal bone covering the adductor chamber has long held sway in amniote systematics^ 10 , and still represents a common organizational scheme for teaching the Evolutionary history of the group. These discoveries allow us to articulate a detailed and testable hypothesis of fenestral closure along the turtle stem. Our results suggest that Eunotosaurus represents a crucially important link in a chain that will eventually lead to consilience in reptile systematics, paving the way for synthetic studies of amniote evolution and development. The evolution of the early reptiles is a complicated story and one particular event — the inferred transformation between an ancestral turtle with a diapsid skull (with openings in the skull behind each eye) to the closed, anapsid condition of modern turtles — has remained elusive in the fossil record. Eunotosaurus africanus is an unusual reptile that lived 260 million years ago in what is now South Africa. Its oddities include flared and expanded ribs, which some have suggested represent the early stirrings of testudinates (turtles and tortoises). Computed tomography and phylogenetic analysis of the E. africanus skull now suggests that not only is Eunotosaurus an early relative of the group, but that it is a diapsid caught in the act of evolving towards a secondarily anapsid state.
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Evolutionary Origin of the turtle skull
Nature, 2015Co-Authors: Gaberiel Bever, Tyler R. Lyson, Daniel J Field, Bhart-anjan S. BhullarAbstract:Transitional fossils informing the Origin of turtles are among the most sought-after discoveries in palaeontology. Despite strong genomic evidence indicating that turtles evolved from within the diapsid radiation (which includes all other living reptiles), evidence of the inferred transformation between an ancestral turtle with an open, diapsid skull to the closed, anapsid condition of modern turtles remains elusive. Here we use high-resolution computed tomography and a novel character/taxon matrix to study the skull of Eunotosaurus africanus, a 260-million-year-old fossil reptile from the Karoo Basin of South Africa, whose distinctive postcranial skeleton shares many unique features with the shelled body plan of turtles. Scepticism regarding the status of Eunotosaurus as the earliest stem turtle arises from the possibility that these shell-related features are the products of Evolutionary convergence. Our phylogenetic analyses indicate strong cranial support for Eunotosaurus as a critical transitional form in turtle evolution, thus fortifying a 40-million-year extension to the turtle stem and moving the ecological context of its Origin back onto land. Furthermore, we find unexpected evidence that Eunotosaurus is a diapsid reptile in the process of becoming secondarily anapsid. This is important because categorizing the skull based on the number of openings in the complex of dermal bone covering the adductor chamber has long held sway in amniote systematics, and still represents a common organizational scheme for teaching the Evolutionary history of the group. These discoveries allow us to articulate a detailed and testable hypothesis of fenestral closure along the turtle stem. Our results suggest that Eunotosaurus represents a crucially important link in a chain that will eventually lead to consilience in reptile systematics, paving the way for synthetic studies of amniote evolution and development.
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Evolutionary Origin of the turtle shell
Current Biology, 2013Co-Authors: Tyler R. Lyson, Gabe S Bever, Torsten M Scheyer, Allison Y Hsiang, Jacques A GauthierAbstract:The Origin of the turtle shell has perplexed biologists for more than two centuries. It was not until Odontochelys semitestacea was discovered, however, that the fossil and developmental data could be synthesized into a model of shell assembly that makes predictions for the as-yet unestablished history of the turtle stem group. We build on this model by integrating novel data for Eunotosaurus africanus-a Late Guadalupian (∼260 mya) Permian reptile inferred to be an early stem turtle. Eunotosaurus expresses a number of relevant characters, including a reduced number of elongate trunk vertebrae (nine), nine pairs of T-shaped ribs, inferred loss of intercostal muscles, reorganization of respiratory muscles to the ventral side of the ribs, (sub)dermal outgrowth of bone from the developing perichondral collar of the ribs, and paired gastralia that lack both lateral and median elements. These features conform to the predicted sequence of character acquisition and provide further support that E. africanus, O. semitestacea, and Proganochelys quenstedti represent successive divergences from the turtle stem lineage. The initial transformations of the model thus occurred by the Middle Permian, which is congruent with molecular-based divergence estimates for the lineage, and remain viable whether turtles Originated inside or outside crown Diapsida.
Stephen A. Green - One of the best experts on this subject based on the ideXlab platform.
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Ancient Evolutionary Origin of vertebrate enteric neurons from trunk-derived neural crest
Nature, 2017Co-Authors: Stephen A. Green, Marianne E. BronnerAbstract:In gnathostomes (jawed vertebrates), the ganglia of the enteric nervous system are populated from the vagal neural crest, which invades the gut at the anterior end and makes its way to the back. In mammals, however, Schwann cell precursors also contribute to these ganglia. This second mechanism might in fact be a relic of ancient times rather than a mammalian innovation. Here, Marianne Bronner and colleagues show that the vagal neural crest plays no part in the population of the enteric nervous system in a jawless vertebrate, the sea lamprey, in which the whole gut is populated by Schwann-cell-precursor-like cells from the trunk neural crest. The enteric nervous system of jawed vertebrates arises primarily from vagal neural crest cells that migrate to the foregut and subsequently colonize and innervate the entire gastrointestinal tract. Here we examine development of the enteric nervous system in the basal jawless vertebrate the sea lamprey ( Petromyzon marinus ) to gain insight into its Evolutionary Origin. Surprisingly, we find no evidence for the existence of a vagally derived enteric neural crest population in the lamprey. Rather, labelling with the lipophilic dye DiI shows that late-migrating cells, Originating from the trunk neural tube and associated with nerve fibres, differentiate into neurons within the gut wall and typhlosole. We propose that these trunk-derived neural crest cells may be homologous to Schwann cell precursors, recently shown in mammalian embryos to populate post-embryonic parasympathetic ganglia^ 1 , 2 , including enteric ganglia^ 3 . Our results suggest that neural-crest-derived Schwann cell precursors made an important contribution to the ancient enteric nervous system of early jawless vertebrates, a role that was largely subsumed by vagal neural crest cells in early gnathostomes. Whereas the enteric nervous system of jawed vertebrates is derived largely from the vagal neural crest, that of the sea lamprey ( Petromyzon marinus ) is populated by trunk-derived neural crest cells that may be homologous to Schwann cell precursors.
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Ancient Evolutionary Origin of vertebrate enteric neurons from trunk-derived neural crest.
Nature, 2017Co-Authors: Stephen A. Green, Marianne E. BronnerAbstract:The enteric nervous system of jawed vertebrates arises primarily from vagal neural crest cells that migrate to the foregut and subsequently colonize and innervate the entire gastrointestinal tract. Here we examine development of the enteric nervous system in the basal jawless vertebrate the sea lamprey (Petromyzon marinus) to gain insight into its Evolutionary Origin. Surprisingly, we find no evidence for the existence of a vagally derived enteric neural crest population in the lamprey. Rather, labelling with the lipophilic dye DiI shows that late-migrating cells, Originating from the trunk neural tube and associated with nerve fibres, differentiate into neurons within the gut wall and typhlosole. We propose that these trunk-derived neural crest cells may be homologous to Schwann cell precursors, recently shown in mammalian embryos to populate post-embryonic parasympathetic ganglia, including enteric ganglia. Our results suggest that neural-crest-derived Schwann cell precursors made an important contribution to the ancient enteric nervous system of early jawless vertebrates, a role that was largely subsumed by vagal neural crest cells in early gnathostomes.
Bhart-anjan S. Bhullar - One of the best experts on this subject based on the ideXlab platform.
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Evolutionary Origin of the turtle skull
Nature, 2015Co-Authors: Gaberiel Bever, Tyler R. Lyson, Daniel J Field, Bhart-anjan S. BhullarAbstract:Computed tomography and phylogenetic analysis of the Eunotosaurus africanus skull suggests that not only is Eunotosaurus an early relative of the group that eventually evolved into turtles, but that it is also a diapsid caught in the act of evolving towards a secondarily anapsid state. Transitional fossils informing the Origin of turtles are among the most sought-after discoveries in palaeontology^ 1 , 2 , 3 , 4 , 5 . Despite strong genomic evidence indicating that turtles evolved from within the diapsid radiation (which includes all other living reptiles^ 6 , 7 ), evidence of the inferred transformation between an ancestral turtle with an open, diapsid skull to the closed, anapsid condition of modern turtles remains elusive. Here we use high-resolution computed tomography and a novel character/taxon matrix to study the skull of Eunotosaurus africanus , a 260-million-year-old fossil reptile from the Karoo Basin of South Africa, whose distinctive postcranial skeleton shares many unique features with the shelled body plan of turtles^ 2 , 3 , 4 . Scepticism regarding the status of Eunotosaurus as the earliest stem turtle arises from the possibility that these shell-related features are the products of Evolutionary convergence. Our phylogenetic analyses indicate strong cranial support for Eunotosaurus as a critical transitional form in turtle evolution, thus fortifying a 40-million-year extension to the turtle stem and moving the ecological context of its Origin back onto land^ 8 , 9 . Furthermore, we find unexpected evidence that Eunotosaurus is a diapsid reptile in the process of becoming secondarily anapsid. This is important because categorizing the skull based on the number of openings in the complex of dermal bone covering the adductor chamber has long held sway in amniote systematics^ 10 , and still represents a common organizational scheme for teaching the Evolutionary history of the group. These discoveries allow us to articulate a detailed and testable hypothesis of fenestral closure along the turtle stem. Our results suggest that Eunotosaurus represents a crucially important link in a chain that will eventually lead to consilience in reptile systematics, paving the way for synthetic studies of amniote evolution and development. The evolution of the early reptiles is a complicated story and one particular event — the inferred transformation between an ancestral turtle with a diapsid skull (with openings in the skull behind each eye) to the closed, anapsid condition of modern turtles — has remained elusive in the fossil record. Eunotosaurus africanus is an unusual reptile that lived 260 million years ago in what is now South Africa. Its oddities include flared and expanded ribs, which some have suggested represent the early stirrings of testudinates (turtles and tortoises). Computed tomography and phylogenetic analysis of the E. africanus skull now suggests that not only is Eunotosaurus an early relative of the group, but that it is a diapsid caught in the act of evolving towards a secondarily anapsid state.
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Evolutionary Origin of the turtle skull
Nature, 2015Co-Authors: Gaberiel Bever, Tyler R. Lyson, Daniel J Field, Bhart-anjan S. BhullarAbstract:Transitional fossils informing the Origin of turtles are among the most sought-after discoveries in palaeontology. Despite strong genomic evidence indicating that turtles evolved from within the diapsid radiation (which includes all other living reptiles), evidence of the inferred transformation between an ancestral turtle with an open, diapsid skull to the closed, anapsid condition of modern turtles remains elusive. Here we use high-resolution computed tomography and a novel character/taxon matrix to study the skull of Eunotosaurus africanus, a 260-million-year-old fossil reptile from the Karoo Basin of South Africa, whose distinctive postcranial skeleton shares many unique features with the shelled body plan of turtles. Scepticism regarding the status of Eunotosaurus as the earliest stem turtle arises from the possibility that these shell-related features are the products of Evolutionary convergence. Our phylogenetic analyses indicate strong cranial support for Eunotosaurus as a critical transitional form in turtle evolution, thus fortifying a 40-million-year extension to the turtle stem and moving the ecological context of its Origin back onto land. Furthermore, we find unexpected evidence that Eunotosaurus is a diapsid reptile in the process of becoming secondarily anapsid. This is important because categorizing the skull based on the number of openings in the complex of dermal bone covering the adductor chamber has long held sway in amniote systematics, and still represents a common organizational scheme for teaching the Evolutionary history of the group. These discoveries allow us to articulate a detailed and testable hypothesis of fenestral closure along the turtle stem. Our results suggest that Eunotosaurus represents a crucially important link in a chain that will eventually lead to consilience in reptile systematics, paving the way for synthetic studies of amniote evolution and development.
Oleg Smirnov - One of the best experts on this subject based on the ideXlab platform.
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On the Evolutionary Origin of Prospect Theory Preferences
The Journal of Politics, 2007Co-Authors: Rose Mcdermott, James H. Fowler, Oleg SmirnovAbstract:Prospect theory scholars have identified important human decision-making biases, but they have been conspicuously silent on the question of the Origin of these biases. Here we create a model that shows preferences consistent with prospect theory may have an Origin in Evolutionary psychology. Specifically, we derive a model from risk-sensitive optimal foraging theory to generate an explanation for the Origin and function of context-dependent risk aversion and risk seeking behavior. Although this model suggests that human cognitive architecture evolved to solve particular adaptive problems related to finding sufficient food resources to survive, we argue that this same architecture persists and is utilized in other survival-related decisions that are critical to understanding political outcomes. In particular, we identify important departures from standard results when we incorporate prospect theory into theories of spatial voting and legislator behavior, international bargaining and conflict, and economic development and reform.
