Publication Date:
2015-08-11
Description:
The sudden appearance of the neural crest and neurogenic placodes in early branching vertebrates has puzzled biologists for over a century. These embryonic tissues contribute to the development of the cranium and associated sensory organs, which were crucial for the evolution of the vertebrate "new head". A previous study suggests that rudimentary neural crest cells existed in ancestral chordates. However, the evolutionary origins of neurogenic placodes have remained obscure owing to a paucity of embryonic data from tunicates, the closest living relatives to those early vertebrates. Here we show that the tunicate Ciona intestinalis exhibits a proto-placodal ectoderm (PPE) that requires inhibition of bone morphogenetic protein (BMP) and expresses the key regulatory determinant Six1/2 and its co-factor Eya, a developmental process conserved across vertebrates. The Ciona PPE is shown to produce ciliated neurons that express genes for gonadotropin-releasing hormone (GnRH), a G-protein-coupled receptor for relaxin-3 (RXFP3) and a functional cyclic nucleotide-gated channel (CNGA), which suggests dual chemosensory and neurosecretory activities. These observations provide evidence that Ciona has a neurogenic proto-placode, which forms neurons that appear to be related to those derived from the olfactory placode and hypothalamic neurons of vertebrates. We discuss the possibility that the PPE-derived GnRH neurons of Ciona resemble an ancestral cell type, a progenitor to the complex neuronal circuit that integrates sensory information and neuroendocrine functions in vertebrates.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Abitua, Philip Barron -- Gainous, T Blair -- Kaczmarczyk, Angela N -- Winchell, Christopher J -- Hudson, Clare -- Kamata, Kaori -- Nakagawa, Masashi -- Tsuda, Motoyuki -- Kusakabe, Takehiro G -- Levine, Michael -- NS076542/NS/NINDS NIH HHS/ -- England -- Nature. 2015 Aug 27;524(7566):462-5. doi: 10.1038/nature14657. Epub 2015 Aug 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Integrative Genomics, Division of Genetics, Genomics and Development, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA. ; Sorbonne Universites, Universite Pierre et Marie Curie, Centre National de la Recherche Scientifique, Laboratoire de Biologie du Developpement de Villefranche-sur-mer, Observatoire Oceanologique, 06230 Villefranche-sur-mer, France. ; Graduate School of Life Science, University of Hyogo, Kamigori, Hyogo 678-1297, Japan. ; Institute for Integrative Neurobiology and Department of Biology, Faculty of Science and Engineering, Konan University, Kobe 658-8501, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26258298" target="_blank"〉PubMed〈/a〉
Keywords:
Animals
;
Body Patterning
;
Bone Morphogenetic Proteins
;
Ciona intestinalis/*cytology/*embryology/genetics/metabolism
;
Ectoderm/metabolism
;
Gonadotropin-Releasing Hormone/metabolism
;
HEK293 Cells
;
Homeodomain Proteins/metabolism
;
Humans
;
Intracellular Signaling Peptides and Proteins/metabolism
;
Larva/cytology/metabolism
;
Molecular Sequence Data
;
Neurons/*cytology/metabolism
;
Protein Tyrosine Phosphatases/metabolism
;
Receptors, G-Protein-Coupled/metabolism
;
Vertebrates/*anatomy & histology/*embryology/physiology
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
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