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Papadogiannis V, Hockman D, Mercurio S, Ramsay C, Hintze M, Patthey C, Streit A, Shimeld SM. Evolution of the expression and regulation of the nuclear hormone receptor ERR gene family in the chordate lineage. Dev Biol 2023; 504:12-24. [PMID: 37696353 DOI: 10.1016/j.ydbio.2023.09.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 09/01/2023] [Accepted: 09/09/2023] [Indexed: 09/13/2023]
Abstract
The Estrogen Related Receptor (ERR) nuclear hormone receptor genes have a wide diversity of roles in vertebrate development. In embryos, ERR genes are expressed in several tissues, including the central and peripheral nervous systems. Here we seek to establish the evolutionary history of chordate ERR genes, their expression and their regulation. We examine ERR expression in mollusc, amphioxus and sea squirt embryos, finding the single ERR orthologue is expressed in the nervous system in all three, with muscle expression also found in the two chordates. We show that most jawed vertebrates and lampreys have four ERR paralogues, and that vertebrate ERR genes were ancestrally linked to Estrogen Receptor genes. One of the lamprey paralogues shares conserved expression domains with jawed vertebrate ERRγ in the embryonic vestibuloacoustic ganglion, eye, brain and spinal cord. Hypothesising that conserved expression derives from conserved regulation, we identify a suite of pan-vertebrate conserved non-coding sequences in ERR introns. We use transgenesis in lamprey and chicken embryos to show that these sequences are regulatory and drive reporter gene expression in the nervous system. Our data suggest an ancient association between ERR and the nervous system, including expression in cells associated with photosensation and mechanosensation. This includes the origin in the vertebrate common ancestor of a suite of regulatory elements in the 3' introns that drove nervous system expression and have been conserved from this point onwards.
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Affiliation(s)
| | - Dorit Hockman
- Division of Cell Biology, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa; Neuroscience Institute, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Silvia Mercurio
- Department of Environmental Science and Policy, Università Degli Studi di Milano, Via Celoria 2, 20133, Milano, Italy
| | - Claire Ramsay
- Department of Biology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK
| | - Mark Hintze
- Centre for Craniofacial & Regenerative Biology, Faculty of Dentistry, Oral and Craniofacial Sciences, King's College London, London, UK
| | - Cedric Patthey
- Department of Radiosciences, Umeå University, 901 85, Umeå, Sweden
| | - Andrea Streit
- Centre for Craniofacial & Regenerative Biology, Faculty of Dentistry, Oral and Craniofacial Sciences, King's College London, London, UK
| | - Sebastian M Shimeld
- Department of Biology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK.
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2
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Diaz C, Glover JC. The Vestibular Column in the Mouse: A Rhombomeric Perspective. Front Neuroanat 2022; 15:806815. [PMID: 35173589 PMCID: PMC8842660 DOI: 10.3389/fnana.2021.806815] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 12/20/2021] [Indexed: 11/30/2022] Open
Abstract
The vestibular column is located in the hindbrain between the sensory auditory (dorsal) and trigeminal (ventral) columns, spanning rhombomeres r1 (or r2) to r9. It contains the vestibular nuclear complex that receives sensory innervation from the labyrinthine end organs in the inner ear. Gene expression studies and experimental manipulations of developmental genes, particularly Hox genes and other developmental patterning genes, are providing insight into the morphological and functional organization of the vestibular nuclear complex, particularly from a segmental standpoint. Here, we will review studies of the classical vestibular nuclei and of vestibular projection neurons that innervate distinct targets in relation to individual rhombomeres and the expression of specific genes. Studies in different species have demonstrated that the vestibular complex is organized into a hodological mosaic that relates axon trajectory and target to specific hindbrain rhombomeres and intrarhombomeric domains, with a molecular underpinning in the form of transcription factor signatures, which has been highly conserved during the evolution of the vertebrate lineage.
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Affiliation(s)
- Carmen Diaz
- Department of Medical Sciences, School of Medicine and Institute for Research in Neurological Disabilities, University of Castilla-La Mancha, Albacete, Spain
- *Correspondence: Carmen Diaz,
| | - Joel C. Glover
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- Joel C. Glover,
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3
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Shen G, Wu J, Lin Y, Hua X, Xia Q, Zhao P. Estrogen-Related Receptor Influences the Hemolymph Glucose Content by Regulating Midgut Trehalase Gene Expression in the Last Instar Larvae of Bombyx mori. Int J Mol Sci 2021; 22:4343. [PMID: 33919382 PMCID: PMC8122577 DOI: 10.3390/ijms22094343] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 04/14/2021] [Accepted: 04/15/2021] [Indexed: 01/13/2023] Open
Abstract
The expression of trehalase in the midgut of insects plays an important role in glucose supply to the hemolymph. Energy metabolism is usually regulated by the estrogen-related receptor (ERR). A decrease in ATP levels is caused by the ERR hindering glycolysis. However, the relationship between trehalose accumulation and ERR expression is still unclear. Here, we found that silkworm ERR (BmERR) is concentrated and BmERR expression is strongly correlated with trehalase in the midgut during the last instar silkworm larval stage. We cloned the promoter of the trehalase from Bombyx mori (BmTreh) and found that the ERR bound directly to the core response elements of the promoter. Cell level interference and the overexpression of ERR can reduce or enhance BmTreh transcription and promoter activity. Overexpressed transgenic BmERR can significantly increase the expression of BmTreh in the midgut of the last instar silkworm larvae, thereby hydrolyzing trehalose into glucose and releasing it into the hemolymph. Additionally, increased hemolymph glucose content reduces silkworm pupa weight but does not affect silk protein production from the silk gland. Our results suggest a novel function for BmERR through its involvement in BmTreh regulation and expand the understanding of ERR functions in insect trehalose metabolism.
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Affiliation(s)
- Guanwang Shen
- Biological Science Research Center, Southwest University, Chongqing 400716, China; (G.S.); (J.W.); (Y.L.); (X.H.); (Q.X.)
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
| | - Jinxin Wu
- Biological Science Research Center, Southwest University, Chongqing 400716, China; (G.S.); (J.W.); (Y.L.); (X.H.); (Q.X.)
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
| | - Ying Lin
- Biological Science Research Center, Southwest University, Chongqing 400716, China; (G.S.); (J.W.); (Y.L.); (X.H.); (Q.X.)
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
| | - Xiaoting Hua
- Biological Science Research Center, Southwest University, Chongqing 400716, China; (G.S.); (J.W.); (Y.L.); (X.H.); (Q.X.)
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
| | - Qingyou Xia
- Biological Science Research Center, Southwest University, Chongqing 400716, China; (G.S.); (J.W.); (Y.L.); (X.H.); (Q.X.)
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
| | - Ping Zhao
- Biological Science Research Center, Southwest University, Chongqing 400716, China; (G.S.); (J.W.); (Y.L.); (X.H.); (Q.X.)
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China
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4
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Miglioli A, Canesi L, Gomes IDL, Schubert M, Dumollard R. Nuclear Receptors and Development of Marine Invertebrates. Genes (Basel) 2021; 12:genes12010083. [PMID: 33440651 PMCID: PMC7827873 DOI: 10.3390/genes12010083] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 12/31/2020] [Accepted: 01/04/2021] [Indexed: 12/12/2022] Open
Abstract
Nuclear Receptors (NRs) are a superfamily of transcription factors specific to metazoans that have the unique ability to directly translate the message of a signaling molecule into a transcriptional response. In vertebrates, NRs are pivotal players in countless processes of both embryonic and adult physiology, with embryonic development being one of the most dynamic periods of NR activity. Accumulating evidence suggests that NR signaling is also a major regulator of development in marine invertebrates, although ligands and transactivation dynamics are not necessarily conserved with respect to vertebrates. The explosion of genome sequencing projects and the interpretation of the resulting data in a phylogenetic context allowed significant progress toward an understanding of NR superfamily evolution, both in terms of molecular activities and developmental functions. In this context, marine invertebrates have been crucial for characterizing the ancestral states of NR-ligand interactions, further strengthening the importance of these organisms in the field of evolutionary developmental biology.
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Affiliation(s)
- Angelica Miglioli
- Laboratoire de Biologie du Développement de Villefranche-sur-Mer (LBDV), Institut de la Mer de Villefranche, Sorbonne Université, CNRS, 181 Chemin du Lazaret, 06230 Villefranche-sur-Mer, France; (A.M.); (I.D.L.G.); (M.S.)
- Dipartimento di Scienze della Terra, dell’Ambiente e della Vita (DISTAV), Università degli Studi di Genova, Corso Europa 26, 16132 Genova, Italy;
| | - Laura Canesi
- Dipartimento di Scienze della Terra, dell’Ambiente e della Vita (DISTAV), Università degli Studi di Genova, Corso Europa 26, 16132 Genova, Italy;
| | - Isa D. L. Gomes
- Laboratoire de Biologie du Développement de Villefranche-sur-Mer (LBDV), Institut de la Mer de Villefranche, Sorbonne Université, CNRS, 181 Chemin du Lazaret, 06230 Villefranche-sur-Mer, France; (A.M.); (I.D.L.G.); (M.S.)
| | - Michael Schubert
- Laboratoire de Biologie du Développement de Villefranche-sur-Mer (LBDV), Institut de la Mer de Villefranche, Sorbonne Université, CNRS, 181 Chemin du Lazaret, 06230 Villefranche-sur-Mer, France; (A.M.); (I.D.L.G.); (M.S.)
| | - Rémi Dumollard
- Laboratoire de Biologie du Développement de Villefranche-sur-Mer (LBDV), Institut de la Mer de Villefranche, Sorbonne Université, CNRS, 181 Chemin du Lazaret, 06230 Villefranche-sur-Mer, France; (A.M.); (I.D.L.G.); (M.S.)
- Correspondence:
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5
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Ren Q, Zhong Y, Huang X, Leung B, Xing C, Wang H, Hu G, Wang Y, Shimeld SM, Li G. Step-wise evolution of neural patterning by Hedgehog signalling in chordates. Nat Ecol Evol 2020; 4:1247-1255. [DOI: 10.1038/s41559-020-1248-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 06/15/2020] [Indexed: 11/09/2022]
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6
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Gomes IDL, Gazo I, Besnardeau L, Hebras C, McDougall A, Dumollard R. Potential roles of nuclear receptors in mediating neurodevelopmental toxicity of known endocrine-disrupting chemicals in ascidian embryos. Mol Reprod Dev 2019; 86:1333-1347. [PMID: 31215734 DOI: 10.1002/mrd.23219] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Revised: 05/15/2019] [Accepted: 05/20/2019] [Indexed: 12/17/2022]
Abstract
Endocrine Disrupting Chemicals (EDCs) are molecules able to interfere with the vertebrate hormonal system in different ways, a major one being the modification of the activity of nuclear receptors (NRs). Several NRs are expressed in the vertebrate brain during embryonic development and these NRs are suspected to be responsible for the neurodevelopmental defects induced by exposure to EDCs in fishes or amphibians and to participate in several neurodevelopmental disorders observed in humans. Known EDCs exert toxicity not only on vertebrate forms of marine life but also on marine invertebrates. However, because hormonal systems of invertebrates are poorly understood, it is not clear whether the teratogenic effects of known EDCs are because of endocrine disruption. The most conserved actors of endocrine systems are the NRs which are present in all metazoan genomes but their functions in invertebrate organisms are still insufficiently characterized. EDCs like bisphenol A have recently been shown to affect neurodevelopment in marine invertebrate chordates called ascidians. Because such phenotypes can be mediated by NRs expressed in the ascidian embryo, we review all the information available about NRs expression during ascidian embryogenesis and discuss their possible involvement in the neurodevelopmental phenotypes induced by EDCs.
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Affiliation(s)
- Isa D L Gomes
- Sorbonne Université/CNRS, Institut de la Mer, UMR7009 Laboratoire de Biologie du Développement, 06230, Villefranche-sur-Mer, France
| | - Ievgeniia Gazo
- South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, Research Institute of Fish Culture and Hydrobiology, Faculty of Fisheries and Protection of Waters, University of South Bohemia in Ceske Budejovice, Zátiší 728/II, 389 25, Vodňany, Czech Republic
| | - Lydia Besnardeau
- Sorbonne Université/CNRS, Institut de la Mer, UMR7009 Laboratoire de Biologie du Développement, 06230, Villefranche-sur-Mer, France
| | - Céline Hebras
- Sorbonne Université/CNRS, Institut de la Mer, UMR7009 Laboratoire de Biologie du Développement, 06230, Villefranche-sur-Mer, France
| | - Alex McDougall
- Sorbonne Université/CNRS, Institut de la Mer, UMR7009 Laboratoire de Biologie du Développement, 06230, Villefranche-sur-Mer, France
| | - Rémi Dumollard
- Sorbonne Université/CNRS, Institut de la Mer, UMR7009 Laboratoire de Biologie du Développement, 06230, Villefranche-sur-Mer, France
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7
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Molecular Profiling Defines Evolutionarily Conserved Transcription Factor Signatures of Major Vestibulospinal Neuron Groups. eNeuro 2019; 6:eN-NWR-0475-18. [PMID: 30899776 PMCID: PMC6426439 DOI: 10.1523/eneuro.0475-18.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 01/04/2019] [Accepted: 01/25/2019] [Indexed: 12/24/2022] Open
Abstract
Vestibulospinal neurons are organized into discrete groups projecting from brainstem to spinal cord, enabling vertebrates to maintain proper balance and posture. The two largest groups are the lateral vestibulospinal tract (LVST) group and the contralateral medial vestibulospinal tract (cMVST) group, with different projection lateralities and functional roles. In search of a molecular basis for these differences, we performed RNA sequencing on LVST and cMVST neurons from mouse and chicken embryos followed by immunohistofluorescence validation. Focusing on transcription factor (TF)-encoding genes, we identified TF signatures that uniquely distinguish the LVST from the cMVST group and further parse different rhombomere-derived portions comprising the cMVST group. Immunohistofluorescence assessment of the CNS from spinal cord to cortex demonstrated that these TF signatures are restricted to the respective vestibulospinal groups and some neurons in their immediate vicinity. Collectively, these results link the combinatorial expression of TFs to developmental and functional subdivisions within the vestibulospinal system.
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8
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Zhang JJ, Xi GS. Morphological changes in different caste adult ant specificities of Polyrhachis vicina Roger (Hymenoptera, Formicidae) caused in estrogen-related receptor. Gen Comp Endocrinol 2018; 266:29-37. [PMID: 29746854 DOI: 10.1016/j.ygcen.2018.04.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 03/11/2018] [Accepted: 04/02/2018] [Indexed: 11/29/2022]
Abstract
The estrogen-related receptor (ERR) gene is a member of the nuclear receptor subfamily. Previous studies have indicated that ERR plays important roles in regulating insect growth and development. How ERR is associated with ant caste specificities remains unclear. In this study, we attempted to identify the role of ERR in the regulation of different adult caste specificities of Polyrhachis vicina Roger. Significant variations were detected in the ants including PvERR expressions, some physiological indexes and morphological traits including survival rate, body weight, body length, head width and abdominal appearance by different techniques. The results revealed that when PvERR expressions is up-regulated, boundaries of the abdominal segments were indistinct on the ventral side of the abdomen in males. Down-regulation of PvERR expressions caused abdominal swelling in males and a distended ventral abdomen in females and workers. Variation in PvERR expressions led to a remarkable decline in ant survival rates, particularly for males. These results indicated that different caste adults appeared to have different degrees of sensitivity in physiological response and morphological changes caused by variation in PvERR expressions. Thus, our data demonstrate that PvERR plays an important role in regulating the different adult caste specificities of P. vicina.
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Affiliation(s)
- Juan-Juan Zhang
- Institute of Zoology, Department of Life Science, Shaanxi Normal University, Xi'an, Shaanxi Province 710119, PR China
| | - Geng-Si Xi
- Institute of Zoology, Department of Life Science, Shaanxi Normal University, Xi'an, Shaanxi Province 710119, PR China.
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9
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Ferran JL, Puelles L. Lessons from Amphioxus Bauplan About Origin of Cranial Nerves of Vertebrates That Innervates Extrinsic Eye Muscles. Anat Rec (Hoboken) 2018; 302:452-462. [PMID: 29659196 DOI: 10.1002/ar.23824] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 10/19/2017] [Accepted: 10/23/2017] [Indexed: 12/23/2022]
Abstract
Amphioxus is the living chordate closest to the ancestral form of vertebrates, and in a key position to reveal essential aspects of the evolution of the brain Bauplan of vertebrates. The dorsal neural cord of this species at the larval stage is characterized by a small cerebral vesicle at its anterior end and a large posterior region. The latter is comparable in some aspects to the hindbrain and spinal cord regions of vertebrates. The rostral end of the cerebral vesicle contains a median pigment spot and associated rows of photoreceptor and other nerve cells; this complex is known as "the frontal eye." However, this is not a complete eye in the sense that it has neither eye muscles nor lens (only a primitive retina-like tissue). Cranial nerves III, IV, and VI take part in the motor control of eye muscles in all vertebrates. Using a recent model that postulates distinct molecularly characterized hypothalamo-prethalamic and mesodiencephalic domains in the early cerebral vesicle of amphioxus, we analyze here possible scenarios for the origin from the common ancestor of cephalochordates and vertebrates of the cranial nerves related with extrinsic eye muscle innervations. Anat Rec, 302:452-462, 2019. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- José Luis Ferran
- Department of Human Anatomy and Psychobiology, School of Medicine, University of Murcia, Murcia, Spain.,Institute of Biomedical Research of Murcia - IMIB, Group of Brain Regionalization and genes of development; Virgen de la Arrixaca University Hospital, University of Murcia, Murcia, Spain
| | - Luis Puelles
- Department of Human Anatomy and Psychobiology, School of Medicine, University of Murcia, Murcia, Spain.,Institute of Biomedical Research of Murcia - IMIB, Group of Brain Regionalization and genes of development; Virgen de la Arrixaca University Hospital, University of Murcia, Murcia, Spain
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10
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Hu G, Li G, Wang H, Wang Y. Hedgehog participates in the establishment of left-right asymmetry during amphioxus development by controlling Cerberus expression. Development 2017; 144:4694-4703. [PMID: 29122841 DOI: 10.1242/dev.157172] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 10/31/2017] [Indexed: 01/01/2023]
Abstract
Correct patterning of left-right (LR) asymmetry is essential during the embryonic development of bilaterians. Hedgehog (Hh) signaling is known to play a role in LR asymmetry development of mouse, chicken and sea urchin embryos by regulating Nodal expression. In this study, we report a novel regulatory mechanism for Hh in LR asymmetry development of amphioxus embryos. Our results revealed that Hh-/- embryos abolish Cerberus (Cer) transcription, with bilaterally symmetric expression of Nodal, Lefty and Pitx In consequence, Hh-/- mutants duplicated left-side structures and lost right-side characters, displaying an abnormal bilaterally symmetric body plan. These LR defects in morphology and gene expression could be rescued by Hh mRNA injection. Our results indicate that Hh participates in amphioxus LR patterning by controlling Cer gene expression. Curiously, however, upregulation of Hh signaling failed to alter the Cer expression pattern or LR morphology in amphioxus embryos, indicating that Hh might not provide an asymmetric cue for Cer expression. In addition, Hh is required for mouth opening in amphioxus, hinting at a homologous relationship between amphioxus and vertebrate mouth development.
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Affiliation(s)
- Guangwei Hu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiangan District, Xiamen, Fujian 361102, China
| | - Guang Li
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiangan District, Xiamen, Fujian 361102, China
| | - Hui Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiangan District, Xiamen, Fujian 361102, China
| | - Yiquan Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiangan District, Xiamen, Fujian 361102, China
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11
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Parker HJ, Krumlauf R. Segmental arithmetic: summing up the Hox gene regulatory network for hindbrain development in chordates. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2017; 6. [PMID: 28771970 DOI: 10.1002/wdev.286] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Revised: 06/13/2017] [Accepted: 06/15/2017] [Indexed: 11/10/2022]
Abstract
Organization and development of the early vertebrate hindbrain are controlled by a cascade of regulatory interactions that govern the process of segmentation and patterning along the anterior-posterior axis via Hox genes. These interactions can be assembled into a gene regulatory network that provides a framework to interpret experimental data, generate hypotheses, and identify gaps in our understanding of the progressive process of hindbrain segmentation. The network can be broadly separated into a series of interconnected programs that govern early signaling, segmental subdivision, secondary signaling, segmentation, and ultimately specification of segmental identity. Hox genes play crucial roles in multiple programs within this network. Furthermore, the network reveals properties and principles that are likely to be general to other complex developmental systems. Data from vertebrate and invertebrate chordate models are shedding light on the origin and diversification of the network. Comprehensive cis-regulatory analyses of vertebrate Hox gene regulation have enabled powerful cross-species gene regulatory comparisons. Such an approach in the sea lamprey has revealed that the network mediating segmental Hox expression was present in ancestral vertebrates and has been maintained across diverse vertebrate lineages. Invertebrate chordates lack hindbrain segmentation but exhibit conservation of some aspects of the network, such as a role for retinoic acid in establishing nested Hox expression domains. These comparisons lead to a model in which early vertebrates underwent an elaboration of the network between anterior-posterior patterning and Hox gene expression, leading to the gene-regulatory programs for segmental subdivision and rhombomeric segmentation. WIREs Dev Biol 2017, 6:e286. doi: 10.1002/wdev.286 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Hugo J Parker
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Robb Krumlauf
- Stowers Institute for Medical Research, Kansas City, MO, USA.,Department of Anatomy and Cell Biology, Kansas University Medical Center, Kansas City, Kansas 66160, USA
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12
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Bozzolan F, Durand N, Demondion E, Bourgeois T, Gassias E, Debernard S. Evidence for a role of oestrogen receptor-related receptor in the regulation of male sexual behaviour in the moth Agrotis ipsilon. INSECT MOLECULAR BIOLOGY 2017; 26:403-413. [PMID: 28370607 DOI: 10.1111/imb.12303] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The oestrogen receptor-related receptors (ERRs) are orphan nuclear receptors that were originally identified on the basis of their close homology to the oestrogen receptors. The three mammalian ERR genes participate in the regulation of vital physiological processes including reproduction, development and metabolic homeostasis. Although unique ERRs have been found in insects, data on the function and regulation of these receptors remain sparse. In the present study, a 2095-bp full-length cDNA encoding an ERR, termed AiERR, was isolated from males of the moth Agrotis ipsilon and deposited in the GenBank database under the accession number KT944662. The predicted AiERR protein shared an overall identity of 47-82% with other known insect and mammalian ERR homologues. AiERR exhibited a broad tissue expression pattern with the detection of one transcript of approximately 2 kb in the primary olfactory centres, the antennal lobes (AL). In adult males, the amount of AiERR mRNA in the AL increased concomitantly with age and responses to the female-emitted sex pheromone. Moreover, AiERR knockdown induced an inhibition in the sex pheromone-orientated flight of male. Using A. ipsilon as a model, our study demonstrates that the insect ERR is critical for the performance of male sexual behaviour, probably by acting on central pheromone processing.
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Affiliation(s)
- F Bozzolan
- UMR 1392, Institut d'Ecologie et des Sciences de l'Environnement de Paris, Département d'Ecologie Sensorielle, Université Paris VI, Paris, France
| | - N Durand
- Laboratoire de Biologie des Ligneux et des Grandes Cultures, INRA, Université d'Orléans, Orléans, France
| | - E Demondion
- UMR 1392, Institut d'Ecologie et des Sciences de l'Environnement de Paris, Département d'Ecologie Sensorielle, INRA, Versailles, France
| | - T Bourgeois
- UMR 1392, Institut d'Ecologie et des Sciences de l'Environnement de Paris, Département d'Ecologie Sensorielle, INRA, Versailles, France
| | - E Gassias
- Institut de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - S Debernard
- UMR 1392, Institut d'Ecologie et des Sciences de l'Environnement de Paris, Département d'Ecologie Sensorielle, Université Paris VI, Paris, France
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13
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Fritzsch B, Elliott KL. Evolution and Development of the Inner Ear Efferent System: Transforming a Motor Neuron Population to Connect to the Most Unusual Motor Protein via Ancient Nicotinic Receptors. Front Cell Neurosci 2017; 11:114. [PMID: 28484373 PMCID: PMC5401870 DOI: 10.3389/fncel.2017.00114] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 04/05/2017] [Indexed: 02/06/2023] Open
Abstract
All craniate chordates have inner ears with hair cells that receive input from the brain by cholinergic centrifugal fibers, the so-called inner ear efferents (IEEs). Comparative data suggest that IEEs derive from facial branchial motor (FBM) neurons that project to the inner ear instead of facial muscles. Developmental data showed that IEEs develop adjacent to FBMs and segregation from IEEs might depend on few transcription factors uniquely associated with IEEs. Like other cholinergic terminals in the peripheral nervous system (PNS), efferent terminals signal on hair cells through nicotinic acetylcholine channels, likely composed out of alpha 9 and alpha 10 units (Chrna9, Chrna10). Consistent with the evolutionary ancestry of IEEs is the even more conserved ancestry of Chrna9 and 10. The evolutionary appearance of IEEs may reflect access of FBMs to a novel target, possibly related to displacement or loss of mesoderm-derived muscle fibers by the ectoderm-derived ear vesicle. Experimental transplantations mimicking this possible aspect of ear evolution showed that different motor neurons of the spinal cord or brainstem form cholinergic synapses on hair cells when ears replace somites or eyes. Transplantation provides experimental evidence in support of the evolutionary switch of FBM neurons to become IEEs. Mammals uniquely evolved a prestin related motor system to cause shape changes in outer hair cells regulated by the IEEs. In summary, an ancient motor neuron population drives in craniates via signaling through highly conserved Chrna receptors a uniquely derived cellular contractility system that is essential for hearing in mammals.
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Lacalli T, Candiani S. Locomotory control in amphioxus larvae: new insights from neurotransmitter data. EvoDevo 2017; 8:4. [PMID: 28239444 PMCID: PMC5314712 DOI: 10.1186/s13227-017-0067-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 02/03/2017] [Indexed: 11/25/2022] Open
Abstract
Amphioxus larvae have a midbrain-level locomotory control center whose overall organization is known from serial TEM reconstructions. How it functions has been a puzzle, owing to uncertainty as to the transmitters used by each class of neurons, but this has recently become clearer. We summarize what is now known, and correct past misconceptions: The large paired neurons at the core of the control center are glutamatergic, and hence excitatory, the commissural neurons are GABAergic, hence probably inhibitory, and both motoneurons and ipsilateral projection neurons are cholinergic, suggesting that the latter, a class of interneurons, may be derived evolutionarily from the former. The data clarify some aspects of how fast and slow swimming are controlled and prevented from interfering with one another, but leave open the source of pacemaker activity, which could reside in the large paired neurons or circuits associated with them. A unusual type of non-synaptic junction links the fast and slow systems, but how these junctions function is open to interpretation, depending chiefly on whether they act to couple adjacent cells independent of cell type, or can have differential effects that vary with cell type. Some evolutionary implications are discussed.
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Affiliation(s)
| | - Simona Candiani
- Laboratory of Developmental Neurobiology, DISTAV, Università di Genova, Genoa, Italy
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Holland LZ. The origin and evolution of chordate nervous systems. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0048. [PMID: 26554041 DOI: 10.1098/rstb.2015.0048] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In the past 40 years, comparisons of developmental gene expression and mechanisms of development (evodevo) joined comparative morphology as tools for reconstructing long-extinct ancestral forms. Unfortunately, both approaches typically give congruent answers only with closely related organisms. Chordate nervous systems are good examples. Classical studies alone left open whether the vertebrate brain was a new structure or evolved from the anterior end of an ancestral nerve cord like that of modern amphioxus. Evodevo plus electron microscopy showed that the amphioxus brain has a diencephalic forebrain, small midbrain, hindbrain and spinal cord with parts of the genetic mechanisms for the midbrain/hindbrain boundary, zona limitans intrathalamica and neural crest. Evodevo also showed how extra genes resulting from whole-genome duplications in vertebrates facilitated evolution of new structures like neural crest. Understanding how the chordate central nervous system (CNS) evolved from that of the ancestral deuterostome has been truly challenging. The majority view is that this ancestor had a CNS with a brain that gave rise to the chordate CNS and, with loss of a discrete brain, to one of the two hemichordate nerve cords. The minority view is that this ancestor had no nerve cord; those in chordates and hemichordates evolved independently. New techniques such as phylostratigraphy may help resolve this conundrum.
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Affiliation(s)
- Linda Z Holland
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA
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16
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Parker HJ, Bronner ME, Krumlauf R. The vertebrate Hox gene regulatory network for hindbrain segmentation: Evolution and diversification: Coupling of a Hox gene regulatory network to hindbrain segmentation is an ancient trait originating at the base of vertebrates. Bioessays 2016; 38:526-38. [PMID: 27027928 DOI: 10.1002/bies.201600010] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Hindbrain development is orchestrated by a vertebrate gene regulatory network that generates segmental patterning along the anterior-posterior axis via Hox genes. Here, we review analyses of vertebrate and invertebrate chordate models that inform upon the evolutionary origin and diversification of this network. Evidence from the sea lamprey reveals that the hindbrain regulatory network generates rhombomeric compartments with segmental Hox expression and an underlying Hox code. We infer that this basal feature was present in ancestral vertebrates and, as an evolutionarily constrained developmental state, is fundamentally important for patterning of the vertebrate hindbrain across diverse lineages. Despite the common ground plan, vertebrates exhibit neuroanatomical diversity in lineage-specific patterns, with different vertebrates revealing variations of Hox expression in the hindbrain that could underlie this diversification. Invertebrate chordates lack hindbrain segmentation but exhibit some conserved aspects of this network, with retinoic acid signaling playing a role in establishing nested domains of Hox expression.
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Affiliation(s)
- Hugo J Parker
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Marianne E Bronner
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Robb Krumlauf
- Stowers Institute for Medical Research, Kansas City, MO, USA.,Department of Anatomy and Cell Biology, Kansas University Medical Center, Kansas City, KS, USA
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Soukup V, Yong LW, Lu TM, Huang SW, Kozmik Z, Yu JK. The Nodal signaling pathway controls left-right asymmetric development in amphioxus. EvoDevo 2015; 6:5. [PMID: 25954501 PMCID: PMC4423147 DOI: 10.1186/2041-9139-6-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 01/27/2015] [Indexed: 11/24/2022] Open
Abstract
Background Nodal is an important determinant of the left-right (LR) body axis in bilaterians, specifying the right side in protostomes and non-chordate deuterostomes as opposed to the left side in chordates. Amphioxus represents an early-branching chordate group, rendering it especially useful for studying the character states that predate the origin of vertebrates. However, its anatomy, involving offset arrangement of axial structures, marked asymmetry of the oropharyngeal region, and, most notably, a mouth positioned on the left side, contrasts with the symmetric arrangement of the corresponding regions in other chordates. Results We show that the Nodal signaling pathway acts to specify the LR axis in the cephalochordate amphioxus in a similar way as in vertebrates. At early neurula stages, Nodal switches from initial bilateral to the left-sided expression and subsequently specifies the left embryonic side. Perturbation of Nodal signaling with small chemical inhibitors (SB505124 and SB431542) alters expression of other members of the pathway and of left/right-sided, organ-specific genes. Upon inhibition, larvae display loss of the innate alternation of both somites and axons of peripheral nerves and loss of left-sided pharyngeal structures, such as the mouth, the preoral pit, and the duct of the club-shaped gland. Concomitantly, the left side displays ectopic expression of otherwise right-sided genes, and the larvae exhibit bilaterally symmetrical morphology, with duplicated endostyle and club-shaped gland structures. Conclusions We demonstrate that Nodal signaling is necessary for establishing the LR embryonic axis and for developing profound asymmetry in amphioxus. Our data suggest that initial symmetry breaking in amphioxus and propagation of the pathway on the left side correspond with the situation in vertebrates. However, the organs that become targets of the pathway differ between amphioxus and vertebrates, which may explain the pronounced asymmetry of its oropharyngeal and axial structures and the left-sided position of the mouth. Electronic supplementary material The online version of this article (doi:10.1186/2041-9139-6-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Vladimir Soukup
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, Prague, 14220 Czech Republic
| | - Luok Wen Yong
- Institute of Cellular and Organismic Biology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 11529 Taiwan
| | - Tsai-Ming Lu
- Institute of Cellular and Organismic Biology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 11529 Taiwan
| | - Song-Wei Huang
- Institute of Cellular and Organismic Biology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 11529 Taiwan
| | - Zbynek Kozmik
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, Prague, 14220 Czech Republic
| | - Jr-Kai Yu
- Institute of Cellular and Organismic Biology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 11529 Taiwan ; Institute of Oceanography, National Taiwan University, 1 Roosevelt Road, Section 4, Taipei, 10617 Taiwan
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Tohmé M, Prud'homme SM, Boulahtouf A, Samarut E, Brunet F, Bernard L, Bourguet W, Gibert Y, Balaguer P, Laudet V. Estrogen-related receptor γ is an in vivo receptor of bisphenol A. FASEB J 2014; 28:3124-33. [PMID: 24744145 DOI: 10.1096/fj.13-240465] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Bisphenol A (BPA) is an endocrine disruptor that displays estrogenic activity. Several reports suggest that BPA may have estrogen receptor-independent effects. In zebrafish, 50 μM BPA exposure induces otic vesicle abnormalities, including otolith aggregation. The purpose of this study was to test if BPA action was mediated in vivo during zebrafish development by the orphan nuclear estrogen related receptor (ERR) γ. Combining pharmacological and functional approaches, we demonstrate that the zebrafish ERRγ mediates BPA-induced malformations in otoliths. Using different bisphenol derivatives, we show that different compounds can induce a similar otolith phenotype than BPA and that the binding affinity of these derivatives to the zebrafish ERRγ correlates with their ability to induce otolith malformations. Morpholino knockdown of ERRγ function suppresses the BPA effect on otoliths whereas overexpression of ERRγ led to a BPA-like otolith phenotype. Moreover, a subphenotypical dose of BPA (1 μM) combined with ERRγ overexpression led to a full-dose (50 μM) BPA otolith phenotype. We therefore conclude that ERRγ mediates the otic vesicle phenotype generated by BPA. Our results suggest that the range of pathways perturbed by this compound and its potential harmful effect are larger than expected.-Tohmé, M., Prud'homme, S. M., Boulahtouf, A., Samarut, E., Brunet, F., Bernard, L., Bourguet, W., Gibert, Y., Balaguer, P., Laudet, V. Estrogen-related receptor γ is an in vivo receptor of bisphenol A.
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Affiliation(s)
- Marie Tohmé
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5242, Université Lyon 1, Université de Lyon, Lyon, France
| | - Sophie M Prud'homme
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5242, Université Lyon 1, Université de Lyon, Lyon, France
| | - Abdel Boulahtouf
- Institut de Recherche en Cancérologie de Montpellier, Institut National de la Santé et de la Recherche Médicale (INSERM) U896, Centre Régional de la Lutte Contre le Cancer Val d'Aurelle Paul Lamarque, Montpellier, France
| | - Eric Samarut
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5242, Université Lyon 1, Université de Lyon, Lyon, France
| | - Frédéric Brunet
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5242, Université Lyon 1, Université de Lyon, Lyon, France
| | - Laure Bernard
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5242, Université Lyon 1, Université de Lyon, Lyon, France
| | - William Bourguet
- INSERM U1054, Centre de Biochimie Structurale, Montpellier, CNRS UMR5048, Universités Montpellier 1 and 2, Montpellier, France; and
| | - Yann Gibert
- Metabolic Genetic Diseases Laboratory, Metabolic Research Unit, Deakin School of Medicine, Waurn Ponds, Victoria, Australia
| | - Patrick Balaguer
- Institut de Recherche en Cancérologie de Montpellier, Institut National de la Santé et de la Recherche Médicale (INSERM) U896, Centre Régional de la Lutte Contre le Cancer Val d'Aurelle Paul Lamarque, Montpellier, France
| | - Vincent Laudet
- Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 5242, Université Lyon 1, Université de Lyon, Lyon, France;
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Deblois G, St-Pierre J, Giguère V. The PGC-1/ERR signaling axis in cancer. Oncogene 2013; 32:3483-90. [PMID: 23208510 DOI: 10.1038/onc.2012.529] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 10/15/2012] [Accepted: 10/15/2012] [Indexed: 12/20/2022]
Abstract
Proliferating cells need to produce a large amount of energy and, at the same time, need to maintain a constant supply of biosynthetic precursors of macromolecules that are used as building blocks for generating new cells. Indeed, many cancer cells undergo a switch from mitochondrial to glycolytic metabolism and display a truncated tricarboxylic acid cycle to match these specific metabolic requirements of proliferation. Understanding the mechanisms by which cancer cells reprogram various metabolic pathways to satisfy their unique bioenergetic requirements has become an active field of research. Concomitantly, it has emerged that members of a family of orphan nuclear receptors known as the estrogen-related receptors (ERRs), working in concert with members of the PPARγ coactivator (PGC)-1 family, act as central transcriptional regulators of metabolic gene networks involved in maintaining energy homeostasis in normal cells. Recent studies have suggested that the PGC-1/ERR transcriptional axis is also important in the metabolic reprogramming of cancer cells. This review focuses on the functional integration of the PGC-1/ERR axis with known oncogenes and the observation that modulation of the activity of this axis can have both pro- and anti-proliferative properties.
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Affiliation(s)
- G Deblois
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
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20
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Lecroisey C, Laudet V, Schubert M. The cephalochordate amphioxus: a key to reveal the secrets of nuclear receptor evolution. Brief Funct Genomics 2012; 11:156-66. [PMID: 22441553 DOI: 10.1093/bfgp/els008] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The members of the nuclear receptor (NR) superfamily are transcription factors characterized by a particular mode of function, which is related to the conserved nature of their molecular structure. NR proteins usually contain a DNA-binding domain (DBD) and a ligand-binding domain (LBD) allowing them to directly bind to DNA and regulate target gene expression in a ligand-dependent manner. In this review, we are summarizing our current understanding of the NR diversity in the cephalochordate amphioxus, which represents the best available proxy for the last common chordate ancestor both in terms of morphology and genome organization. The amphioxus genome encodes 33 NRs, which is more than expected based on its phylogenetic position, with at least one representative of all major NR groups, excepting NR1E and NR1I/J. This elevated number of receptor genes shows that the amphioxus NR complement has experienced some secondary modifications that are most evident in the NR1H group, which is characterized by three members in humans and ten representatives in amphioxus. By highlighting specific examples of the NR repertoire, including the receptors for retinoic acid, thyroid hormone, estrogen and steroids as well as the bile acid and oxysterol receptors of the NR1H group, we are illustrating the functional diversity of these receptors in amphioxus. We conclude that the amphioxus NRs are valuable models for assessing the evolutionary interplay between receptors and their ligands and that more integrative and comparative approaches are required for assessment of the evolutionary plasticity of receptor-ligand interactions revealed by the studies of amphioxus NRs.
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Affiliation(s)
- Claire Lecroisey
- Institut de Génomique Fonctionnelle de Lyon, UCBL, CNRS UMR, ENSL, INRA, Ecole Normale Supérieure de Lyon, France
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Burzynski GM, Reed X, Taher L, Stine ZE, Matsui T, Ovcharenko I, McCallion AS. Systematic elucidation and in vivo validation of sequences enriched in hindbrain transcriptional control. Genome Res 2012; 22:2278-89. [PMID: 22759862 PMCID: PMC3483557 DOI: 10.1101/gr.139717.112] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Illuminating the primary sequence encryption of enhancers is central to understanding the regulatory architecture of genomes. We have developed a machine learning approach to decipher motif patterns of hindbrain enhancers and identify 40,000 sequences in the human genome that we predict display regulatory control that includes the hindbrain. Consistent with their roles in hindbrain patterning, MEIS1, NKX6-1, as well as HOX and POU family binding motifs contributed strongly to this enhancer model. Predicted hindbrain enhancers are overrepresented at genes expressed in hindbrain and associated with nervous system development, and primarily reside in the areas of open chromatin. In addition, 77 (0.2%) of these predictions are identified as hindbrain enhancers on the VISTA Enhancer Browser, and 26,000 (60%) overlap enhancer marks (H3K4me1 or H3K27ac). To validate these putative hindbrain enhancers, we selected 55 elements distributed throughout our predictions and six low scoring controls for evaluation in a zebrafish transgenic assay. When assayed in mosaic transgenic embryos, 51/55 elements directed expression in the central nervous system. Furthermore, 30/34 (88%) predicted enhancers analyzed in stable zebrafish transgenic lines directed expression in the larval zebrafish hindbrain. Subsequent analysis of sequence fragments selected based upon motif clustering further confirmed the critical role of the motifs contributing to the classifier. Our results demonstrate the existence of a primary sequence code characteristic to hindbrain enhancers. This code can be accurately extracted using machine-learning approaches and applied successfully for de novo identification of hindbrain enhancers. This study represents a critical step toward the dissection of regulatory control in specific neuronal subtypes.
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Affiliation(s)
- Grzegorz M Burzynski
- McKusick-Nathans Institute of Genetic Medicine, Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Candiani S, Moronti L, Ramoino P, Schubert M, Pestarino M. A neurochemical map of the developing amphioxus nervous system. BMC Neurosci 2012; 13:59. [PMID: 22676056 PMCID: PMC3484041 DOI: 10.1186/1471-2202-13-59] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 04/27/2012] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Amphioxus, representing the most basal group of living chordates, is the best available proxy for the last invertebrate ancestor of the chordates. Although the central nervous system (CNS) of amphioxus comprises only about 20,000 neurons (as compared to billions in vertebrates), the developmental genetics and neuroanatomy of amphioxus are strikingly vertebrate-like. In the present study, we mapped the distribution of amphioxus CNS cells producing distinctive neurochemicals. To this end, we cloned genes encoding biosynthetic enzymes and/or transporters of the most common neurotransmitters and assayed their developmental expression in the embryo and early larva. RESULTS By single and double in situ hybridization experiments, we identified glutamatergic, GABAergic/glycinergic, serotonergic and cholinergic neurons in developing amphioxus. In addition to characterizing the distribution of excitatory and inhibitory neurons in the developing amphioxus CNS, we observed that cholinergic and GABAergic/glycinergic neurons are segmentally arranged in the hindbrain, whereas serotonergic, glutamatergic and dopaminergic neurons are restricted to specific regions of the cerebral vesicle and the hindbrain. We were further able to identify discrete groups of GABAergic and glutamatergic interneurons and cholinergic motoneurons at the level of the primary motor center (PMC), the major integrative center of sensory and motor stimuli of the amphioxus nerve cord. CONCLUSIONS In this study, we assessed neuronal differentiation in the developing amphioxus nervous system and compiled the first neurochemical map of the amphioxus CNS. This map is a first step towards a full characterization of the neurotransmitter signature of previously described nerve cell types in the amphioxus CNS, such as motoneurons and interneurons.
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Affiliation(s)
- Simona Candiani
- Dipartimento per lo Studio del Territorio e delle sue Risorse, Università di Genova, Viale Benedetto XV, 5, 16132 Genoa, Italy.
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Candiani S, Moronti L, De Pietri Tonelli D, Garbarino G, Pestarino M. A study of neural-related microRNAs in the developing amphioxus. EvoDevo 2011; 2:15. [PMID: 21722366 PMCID: PMC3145563 DOI: 10.1186/2041-9139-2-15] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 07/01/2011] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND MicroRNAs are small noncoding RNAs regulating expression of protein coding genes at post-transcriptional level and controlling several biological processes. At present microRNAs have been identified in various metazoans and seem also to be involved in brain development, neuronal differentiation and subtypes specification. An approach to better understand the role of microRNAs in animal gene expression is to determine temporal and tissue-specific expression patterns of microRNAs in different model organisms. Therefore, we have investigated the expression of six neural related microRNAs in amphioxus, an organism having an important phylogenetic position in terms of understanding the origin and evolution of chordates. RESULTS In amphioxus, all the microRNAs we examined are expressed in specific regions of the CNS, and some of them are correlated with specific cell types. In addition, miR-7, miR-137 and miR-184 are also expressed in endodermal and mesodermal tissues. Several potential targets expressed in the nervous system of amphioxus have been identified by computational prediction and some of them are coexpressed with one or more miRNAs. CONCLUSION We identified six miRNAs that are expressed in the nervous system of amphioxus in a variety of patterns. miR-124 is found in both differentiating and mature neurons, miR-9 in differentiated neurons, miR-7, miR-137 and miR-184 in restricted CNS regions, and miR-183 in cells of sensory organs. Therefore, such amphioxus miRNAs may play important roles in regional patterning and/or specification of neuronal cell types.
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Affiliation(s)
- Simona Candiani
- University of Genoa, Department of Biology, viale Benedetto XV 5, 16132 Genoa, Italy.
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Candiani S, Moronti L, Pennati R, De Bernardi F, Benfenati F, Pestarino M. The synapsin gene family in basal chordates: evolutionary perspectives in metazoans. BMC Evol Biol 2010; 10:32. [PMID: 20113475 PMCID: PMC2825198 DOI: 10.1186/1471-2148-10-32] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Accepted: 01/29/2010] [Indexed: 01/07/2023] Open
Abstract
Background Synapsins are neuronal phosphoproteins involved in several functions correlated with both neurotransmitter release and synaptogenesis. The comprehension of the basal role of the synapsin family is hampered in vertebrates by the existence of multiple synapsin genes. Therefore, studying homologous genes in basal chordates, devoid of genome duplication, could help to achieve a better understanding of the complex functions of these proteins. Results In this study we report the cloning and characterization of the Ciona intestinalis and amphioxus Branchiostoma floridae synapsin transcripts and the definition of their gene structure using available C. intestinalis and B. floridae genomic sequences. We demonstrate the occurrence, in both model organisms, of a single member of the synapsin gene family. Full-length synapsin genes were identified in the recently sequenced genomes of phylogenetically diverse metazoans. Comparative genome analysis reveals extensive conservation of the SYN locus in several metazoans. Moreover, developmental expression studies underline that synapsin is a neuronal-specific marker in basal chordates and is expressed in several cell types of PNS and in many, if not all, CNS neurons. Conclusion Our study demonstrates that synapsin genes are metazoan genes present in a single copy per genome, except for vertebrates. Moreover, we hypothesize that, during the evolution of synapsin proteins, new domains are added at different stages probably to cope up with the increased complexity in the nervous system organization. Finally, we demonstrate that protochordate synapsin is restricted to the post-mitotic phase of CNS development and thereby is a good marker of postmitotic neurons.
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Affiliation(s)
- Simona Candiani
- Department of Biology, University of Genoa, Viale Benedetto XV5, 16132 Genova, Italy.
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Mouriec K, Lareyre JJ, Tong SK, Le Page Y, Vaillant C, Pellegrini E, Pakdel F, Chung BC, Kah O, Anglade I. Early regulation of brain aromatase (cyp19a1b) by estrogen receptors during zebrafish development. Dev Dyn 2010; 238:2641-51. [PMID: 19718764 DOI: 10.1002/dvdy.22069] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Early expression of estrogen receptors (esr) and their role in regulating early expression of cyp19a1b encoding brain aromatase were examined in the brain of zebrafish. Using in toto hybridization and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), a significant increase in the expression of esr1, esr2a, and esr2b was observed between 24 and 48 hours postfertilization (hpf). In toto hybridization demonstrated that esr2a and esr2b, but not esr1, are found in the hypothalamus. Using real-time RT-PCR, an increase in cyp19a1b mRNAs occurs between 24 and 48 hpf, indicating that expression of cyp19a1b is temporally correlated with that of esr. This increase is blocked by the pure anti-estrogen ICI182,780. Furthermore, E2 treatment of cyp19a1b-GFP (green fluorescent protein) transgenic embryos results in appearance of GFP expression in the brain as early as 25 hpf. These results indicate that basal expression of cyp19a1b expression in the brain of developing zebrafish most likely relies upon expression of esr that are fully functional before 25 hpf.
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Affiliation(s)
- K Mouriec
- Neurogenesis And OEstrogens, UMR CNRS 6026, IFR 140, Université de Rennes 1, Rennes, France
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He H, Xi G, Lu X. Molecular cloning, characterization, and expression analysis of an estrogen receptor-related receptor homologue in the cricket, Teleogryllus emma. JOURNAL OF INSECT SCIENCE (ONLINE) 2010; 10:188. [PMID: 21265615 PMCID: PMC3029112 DOI: 10.1673/031.010.18801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The estrogen receptor-related receptors (ERRs) are a group of nuclear receptors that were originally identified on the basis of sequence similarity to estrogen receptors. The three mammalian ERR genes have been implicated in diverse physiological processes ranging from placental development to maintenance of bone density, but the function and regulation of ERRs in invertebrates are not well understood. A homologue of human ERR was isolated from the cricket Teleogryllus emma (Ohmachi and Matsumura) (Orthoptera: Gryllidae). The full-length cDNA of T. emma ERR, termed TeERR, has 1618 base pair (bp) and contains a 5'-untranslated region of 140 bp and a 3'-untranslated region of 272 bp. The open reading frame of TeERR encodes a deduced 401 amino acid peptide with a predicted molecular mass of 45.75 kilodaltons. The results of sequence alignments indicate that the TeERR protein shares an overall identity of 65%-82% with other known ERR homologues, and is most closely related to that of Nasonia vitripennis (Hymenoptera: Pteromalidae) and Apis mellifera (Apidae). Real-time quantitative reverse transcription-polymerase chain reaction was performed to compare the TeERR mRNA expression level at the whole body and gonad during T. emma development. The data revealed that TeERR mRNA is differentially expressed during T. emma development, with the highest expression level in embryos and the lowest in the body of late-instar larvae. The levels of TeERR transcripts also varied throughout gonad development; interestingly testicles had higher higher expression levels than ovaries at every development stage. These results suggest that TeERR has potential significance in the regulation of development in T. emma, due to its expression during different developmental periods.
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Affiliation(s)
- Hui He
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710062, People's Republic of China
| | - Gengsi Xi
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710062, People's Republic of China
| | - Xiao Lu
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710062, People's Republic of China
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Bertrand S, Campo-Paysaa F, Camasses A, García-Fernàndez J, Escrivà H. Actors of the tyrosine kinase receptor downstream signaling pathways in amphioxus. Evol Dev 2009; 11:13-26. [PMID: 19196330 DOI: 10.1111/j.1525-142x.2008.00299.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
One of the major goals of evo-developmentalists is to understand how the genetic mechanisms controlling embryonic development have evolved to create the current diversity of bodyplans that we encounter in the animal kingdom. Tyrosine kinase receptors (RTKs) are transmembrane receptors present in all metazoans known to control several developmental processes. They act via the activation of various cytoplasmic signaling cascades, including the mitogen-activated protein kinase (MAPK), the PI3K/Akt, and the phospholipase C-gamma (PLCgamma)/protein kinase C (PKC) pathways. In order to address the evolution of these three pathways and their involvement during embryogenesis in chordates, we took advantage of the complete genome sequencing of a key evolutionarily positioned species, the cephalochordate amphioxus, and searched for the complete gene set of the three signaling pathways. We found that the amphioxus genome contains all of the most important modules of the RTK-activated cascades, and looked at the embryonic expression of two genes selected from each cascade. Our data suggest that although the PI3K/Akt pathway may have ubiquitous functions, the MAPK and the PLCgamma/PKC cascades may play specific roles in amphioxus development. Together with data known in vertebrates, the expression pattern of PKC in amphioxus suggests that the PLCgamma/PKC cascade was implicated in neural development in the ancestor of all chordates.
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Affiliation(s)
- Stéphanie Bertrand
- Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, edifici annex, planta, 08028 Barcelona, Spain
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Kaltenbach SL, Yu JK, Holland ND. The origin and migration of the earliest-developing sensory neurons in the peripheral nervous system of amphioxus. Evol Dev 2009; 11:142-51. [DOI: 10.1111/j.1525-142x.2009.00315.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Park W, Kim GJ, Choi HS, Vanacker JM, Sohn YC. Conserved properties of a urochordate estrogen receptor-related receptor (ERR) with mammalian ERRalpha. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1789:125-34. [PMID: 18822397 DOI: 10.1016/j.bbagrm.2008.08.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 08/22/2008] [Accepted: 08/23/2008] [Indexed: 11/24/2022]
Abstract
Estrogen receptor-related receptors (ERRs) were the first orphan nuclear receptors identified on the basis of their sequence similarity to the estrogen receptors. Although unique ERRs were found in some marine invertebrates, the molecular functions of these receptors are not well understood. In the present study, we identified three transcript variants of the tunicate Halocynthia roretzi ERR (Hr-ERR), varying in their 3' untranslated regions, and putatively encoding a unique receptor deriving from an ancestor protein common to vertebrate ERRalpha/beta/gamma. Maternal mRNA of Hr-ERR was detected throughout the entire egg cytoplasm and early embryos. Zygotic Hr-ERR was predominantly expressed in the heart, and at lower levels in muscle, stomach, gonad and digestive glands. Electrophoretic mobility shift assay demonstrated that Hr-ERR directly binds to the estrogen-response element (ERE) and ERR-response element (ERRE). Gene reporter assays also showed that Hr-ERR activates transcription through ERE and ERRE. Hr-ERR-mediated transactivation was modulated by various cofactors for mammalian ERRs, such as peroxisome proliferator-activated receptor gamma coactivator 1-alpha and small heterodimer partner. In addition, the ERR antagonists 4-hydroxytamoxifen and diethylstilbestrol inhibited the Hr-ERR-mediated transactivation, whereas Hr-ERR activity on ERE was further induced by genistein, an ERRalpha agonist. Taken together, our results show that Hr-ERR is an unduplicated ERR that however, possesses functional properties common to ERRalpha and not to ERRbeta/gamma.
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Affiliation(s)
- WooDong Park
- Faculty of Marine Bioscience and Technology, Kangnung National University, Gangneung 210-702, Republic of Korea
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Candiani S, Lacalli TC, Parodi M, Oliveri D, Pestarino M. The cholinergic gene locus in amphioxus: molecular characterization and developmental expression patterns. Dev Dyn 2008; 237:1399-411. [PMID: 18407548 DOI: 10.1002/dvdy.21541] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cholinergic gene locus (CGL), consisting of the vesicular acetylcholine transporter (VAChT)/choline acetyltransferase (ChAT) gene, encodes two specific cholinergic neuronal markers used extensively to study cholinergic transmission. In the present work, we isolated the amphioxus homologs of VAChT and ChAT and examined their expression during development. Analysis of the 5' untranslated region of VAChT and ChAT suggests that the splicing of the VAChT/ChAT mRNA has been evolutionarily conserved in amphioxus and mammals. By double whole-mount in situ hybridization, we demonstrate that VAChT and ChAT are coexpressed in the same cells. They are first expressed in four pairs of differentiating cells in the neural plate. Their later expression is primarily in the anterior nerve cord in several types of motoneurons, some of the interneurons and in the receptor cells of the larval ocellus.
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Nuclear hormone receptor signaling in amphioxus. Dev Genes Evol 2008; 218:651-65. [DOI: 10.1007/s00427-008-0251-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Accepted: 09/05/2008] [Indexed: 10/21/2022]
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Teyssier C, Bianco S, Lanvin O, Vanacker JM. The orphan receptor ERRalpha interferes with steroid signaling. Nucleic Acids Res 2008; 36:5350-61. [PMID: 18697814 PMCID: PMC2532727 DOI: 10.1093/nar/gkn520] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 07/30/2008] [Accepted: 07/30/2008] [Indexed: 12/04/2022] Open
Abstract
The estrogen receptor-related receptor alpha (ERRalpha) is an orphan member of the nuclear receptor superfamily that has been shown to interfere with the estrogen-signaling pathway. In this report, we demonstrate that ERRalpha also cross-talks with signaling driven by other steroid hormones. Treatment of human prostatic cells with a specific ERRalpha inverse agonist reduces the expression of several androgen-responsive genes, in a manner that does not involve perturbation of androgen receptor expression or activity. Furthermore, ERRalpha activates the expression of androgen response elements (ARE)-containing promoters, such as that of the prostate cancer marker PSA, in an ARE-dependent manner. In addition, promoters containing a steroid response element can be activated by all members of the ERR orphan receptor subfamily, and this, even in the presence of antisteroid compounds.
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Affiliation(s)
| | | | | | - Jean-Marc Vanacker
- Institut de Génomique Fonctionnelle de Lyon, Université de Lyon; Institut Fédératif Biosciences Gerland Lyon Sud and Université Lyon 1, CNRS, INRA, Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon cedex 07, France
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Paris M, Pettersson K, Schubert M, Bertrand S, Pongratz I, Escriva H, Laudet V. An amphioxus orthologue of the estrogen receptor that does not bind estradiol: insights into estrogen receptor evolution. BMC Evol Biol 2008; 8:219. [PMID: 18655705 PMCID: PMC2529310 DOI: 10.1186/1471-2148-8-219] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Accepted: 07/25/2008] [Indexed: 12/21/2022] Open
Abstract
Background The origin of nuclear receptors (NRs) and the question whether the ancestral NR was a liganded or an unliganded transcription factor has been recently debated. To obtain insight into the evolution of the ligand binding ability of estrogen receptors (ER), we comparatively characterized the ER from the protochordate amphioxus (Branchiostoma floridae), and the ER from lamprey (Petromyzon marinus), a basal vertebrate. Results Extensive phylogenetic studies as well as signature analysis allowed us to confirm that the amphioxus ER (amphiER) and the lamprey ER (lampER) belong to the ER group. LampER behaves as a "classical" vertebrate ER, as it binds to specific DNA Estrogen Responsive Elements (EREs), and is activated by estradiol (E2), the classical ER natural ligand. In contrast, we found that although amphiER binds EREs, it is unable to bind E2 and to activate transcription in response to E2. Among the 7 natural and synthetic ER ligands tested as well as a large repertoire of 14 cholesterol derivatives, only Bisphenol A (an endocrine disruptor with estrogenic activity) bound to amphiER, suggesting that a ligand binding pocket exists within the receptor. Parsimony analysis considering all available ER sequences suggest that the ancestral ER was not able to bind E2 and that this ability evolved specifically in the vertebrate lineage. This result does not support a previous analysis based on ancestral sequence reconstruction that proposed the ancestral steroid receptor to bind estradiol. We show that biased taxonomic sampling can alter the calculation of ancestral sequence and that the previous result might stem from a high proportion of vertebrate ERs in the dataset used to compute the ancestral sequence. Conclusion Taken together, our results highlight the importance of comparative experimental approaches vs ancestral reconstructions for the evolutionary study of endocrine systems: comparative analysis of extant ERs suggests that the ancestral ER did not bind estradiol and that it gained the ability to be regulated by estradiol specifically in the vertebrate lineage, before lamprey split.
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Affiliation(s)
- Mathilde Paris
- Institut de Génomique Fonctionnelle de Lyon, Molecular Zoology team, Université de Lyon, Ecole Normale Supérieure de Lyon, Université Lyon 1, CNRS, INRA, Institut Fédératif 128 Biosciences Gerland Lyon Sud, France.
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Holland LZ, Holland ND, Gilland E. Amphioxus and the evolution of head segmentation. Integr Comp Biol 2008; 48:630-46. [DOI: 10.1093/icb/icn060] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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35
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Lacalli TC. Head organization and the head/trunk relationship in protochordates: problems and prospects. Integr Comp Biol 2008; 48:620-9. [PMID: 21669821 DOI: 10.1093/icb/icn012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The fossil record has been an invaluable aid for reconstructing the major events of vertebrate evolution. There is no comparable record for protochordates, however, which severely limits our knowledge of their ancestral morphology, habits, and mode of life. The alternative is inference based on an interpretation of living protochordates but this is fraught with problems, not least being our own biases of what we think an ancestral chordate ought to look like. Relevant to the present symposium is the problem of head/trunk relationships and whether or not the myotomes of the trunk originally extended into the head in vertebrates. I will review what is currently known of patterns of innervation in tunicates and amphioxus in relation to Romer's somaticovisceral concept of the vertebrate body to show how little progress has been made in resolving this problem. There are, in contrast, surprisingly good prospects for solving some other puzzles concerning chordate origins. Dorsoventral inversion provides a good example. A consensus is now emerging, based largely on molecular data from hemichordates that casts new light on the asymmetry of the head in amphioxus. Specifically, the morphogenetic growth process that reestablishes symmetry in late-stage larvae can now be seen, at least in part, as a recapitulation of past evolutionary events, and this has important implications for the origin and basic organization of the brain.
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Affiliation(s)
- Thurston C Lacalli
- Biology Department, University of Victoria, Victoria, BC, Canada, V8W-3N5
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36
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Collin RW, Kalay E, Tariq M, Peters T, van der Zwaag B, Venselaar H, Oostrik J, Lee K, Ahmed ZM, Çaylan R, Li Y, Spierenburg HA, Eyupoglu E, Heister A, Riazuddin S, Bahat E, Ansar M, Arslan S, Wollnik B, Brunner HG, Cremers CW, Karaguzel A, Ahmad W, Cremers FP, Vriend G, Friedman TB, Riazuddin S, Leal SM, Kremer H. Mutations of ESRRB encoding estrogen-related receptor beta cause autosomal-recessive nonsyndromic hearing impairment DFNB35. Am J Hum Genet 2008; 82:125-38. [PMID: 18179891 PMCID: PMC2253958 DOI: 10.1016/j.ajhg.2007.09.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 09/20/2007] [Accepted: 09/21/2007] [Indexed: 01/09/2023] Open
Abstract
In a large consanguineous family of Turkish origin, genome-wide homozygosity mapping revealed a locus for recessive nonsyndromic hearing impairment on chromosome 14q24.3-q34.12. Fine mapping with microsatellite markers defined the critical linkage interval to a 18.7 cM region flanked by markers D14S53 and D14S1015. This region partially overlapped with the DFNB35 locus. Mutation analysis of ESRRB, a candidate gene in the overlapping region, revealed a homozygous 7 bp duplication in exon 8 in all affected individuals. This duplication results in a frame shift and premature stop codon. Sequence analysis of the ESRRB gene in the affected individuals of the original DFNB35 family and in three other DFNB35-linked consanguineous families from Pakistan revealed four missense mutations. ESRRB encodes the estrogen-related receptor beta protein, and one of the substitutions (p.A110V) is located in the DNA-binding domain of ESRRB, whereas the other three are substitutions (p.L320P, p.V342L, and p.L347P) located within the ligand-binding domain. Molecular modeling of this nuclear receptor showed that the missense mutations are likely to affect the structure and stability of these domains. RNA in situ hybridization in mice revealed that Esrrb is expressed during inner-ear development, whereas immunohistochemical analysis showed that ESRRB is present postnatally in the cochlea. Our data indicate that ESRRB is essential for inner-ear development and function. To our knowledge, this is the first report of pathogenic mutations of an estrogen-related receptor gene.
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37
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Tremblay AM, Giguère V. The NR3B subgroup: an ovERRview. NUCLEAR RECEPTOR SIGNALING 2007; 5:e009. [PMID: 18174917 PMCID: PMC2121319 DOI: 10.1621/nrs.05009] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/13/2007] [Accepted: 10/05/2007] [Indexed: 12/25/2022]
Abstract
Members of the NR3B group of the nuclear receptor superfamily, known as the estrogen-related receptors (ERRs), were the first orphan receptors to be identified two decades ago. Despite the fact that a natural ligand has yet to be associated with the ERRs, considerable knowledge about their mode of action and biological functions has emerged through extensive biochemical, genetic and functional genomics studies. This review describes our current understanding of how the ERRs work as transcription factors and as such, how they control diverse developmental and physiological programs.
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Affiliation(s)
- Annie M Tremblay
- Department of Biochemistry, McGill University and Molecular Oncology Group, McGill University Health Centre, Montréal, Québec, Canada
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38
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Candiani S, Pestarino M, Cattaneo E, Tartari M. Characterization, developmental expression and evolutionary features of the huntingtin gene in the amphioxus Branchiostoma floridae. BMC DEVELOPMENTAL BIOLOGY 2007; 7:127. [PMID: 18005438 PMCID: PMC2206037 DOI: 10.1186/1471-213x-7-127] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Accepted: 11/15/2007] [Indexed: 11/10/2022]
Abstract
BACKGROUND Huntington's disease is an inherited neurodegenerative disorder that is caused by the expansion of an N-terminal polyQ stretch in the huntingtin protein. In order to investigate the hypothesis that huntingtin was already involved in development of the nervous system in the last common ancestor of chordates, we isolated and characterised the huntingtin homologue from the amphioxus Branchiostoma floridae. In the present paper the amphioxus general term must be referred to Branchiostoma floridae. RESULTS In this report, we show that the exon-intron organization of the amphioxus huntingtin gene is highly conserved with that of other vertebrates species. The AmphiHtt protein has two glutamine residues in the position of the typical vertebrate polyQ tract. Sequence conservation is greater along the entire length of the protein than in a previously identified Ciona huntingtin. The first three N-terminal HEAT repeats are highly conserved in vertebrates and amphioxus, although exon rearrangement has occurred in this region. AmphiHtt expression is detectable by in situ hybridization starting from the early neurula stage, where it is found in cells of the neural plate. At later stages, it is retained in the neural compartment but also it appears in limited and well-defined groups of non-neural cells. At subsequent larval stages, AmphiHtt expression is detected in the neural tube, with the strongest signal being present in the most anterior part. CONCLUSION The cloning of amphioxus huntingtin allows to infer that the polyQ in huntingtin was already present 540 million years ago and provides a further element for the study of huntingtin function and its evolution along the deuterostome branch.
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Affiliation(s)
- Simona Candiani
- Department of Biology, University of Genoa, viale Benedetto XV 5, 16132, Genoa, Italy.
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39
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Meulemans D, Bronner-Fraser M. The amphioxus SoxB family: implications for the evolution of vertebrate placodes. Int J Biol Sci 2007; 3:356-64. [PMID: 17713598 PMCID: PMC1950271 DOI: 10.7150/ijbs.3.356] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2007] [Accepted: 08/05/2007] [Indexed: 01/12/2023] Open
Abstract
Cranial placodes are regions of thickened ectoderm that give rise to sense organs and ganglia in the vertebrate head. Homologous structures are proposed to exist in urochordates, but have not been found in cephalochordates, suggesting the first chordates lacked placodes. SoxB genes are expressed in discrete subsets of vertebrate placodes. To investigate how placodes arose and diversified in the vertebrate lineage we isolated the complete set of SoxB genes from amphioxus and analyzed their expression in embryos and larvae. We find that while amphioxus possesses a single SoxB2 gene, it has three SoxB1 paralogs. Like vertebrate SoxB1 genes, one of these paralogs is expressed in non-neural ectoderm destined to give rise to sensory cells. When considered in the context of other amphioxus placode marker orthologs, amphioxus SoxB1 expression suggests a diversity of sensory cell types utilizing distinct placode-type gene programs was present in the first chordates. Our data supports a model for placode evolution and diversification whereby the full complement of vertebrate placodes evolved by serial recruitment of distinct sensory cell specification programs to anterior pre-placodal ectoderm.
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Affiliation(s)
- Daniel Meulemans
- Division of Biology, Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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40
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Rasmussen SLK, Holland LZ, Schubert M, Beaster-Jones L, Holland ND. Amphioxus AmphiDelta: evolution of Delta protein structure, segmentation, and neurogenesis. Genesis 2007; 45:113-22. [PMID: 17299746 DOI: 10.1002/dvg.20278] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The amphioxus genome has a single Delta gene (AmphiDelta) encoding a protein 766 amino acids long. Comparison of Delta proteins of amphioxus and other animals indicates that AmphiDelta retains features of a basal bilaterian Delta protein--in having nine epidermal growth factor (EGF) repeats and also in having characteristic numbers of amino acids separating successive cysteines between and within EGF repeats. During development, AmphiDelta is expressed in the forming somites, in some regions of pharyngeal endoderm, and in cells (presumably differentiating neurons) scattered in both the neural plate and ectoderm. Expression is strongly associated with cells initiating movements to separate themselves from parent epithelia, either en masse by evagination (endoderm and mesoderm) or by delamination as isolated cells (ectoderm). The AmphiDelta-expressing cells delaminating from the ectoderm apparently migrate beneath it as they begin differentiating into probable sensory neurons, suggesting a scenario for the evolutionary origin of the placode-derived neurons of vertebrate cranial ganglia.
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Affiliation(s)
- Stacy L K Rasmussen
- Division of Marine Biology Research, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0202, USA
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41
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Bannister R, Beresford N, May D, Routledge EJ, Jobling S, Rand-Weaver M. Novel estrogen receptor-related Transcripts in Marisa cornuarietis; a freshwater snail with reported sensitivity to estrogenic chemicals. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2007; 41:2643-50. [PMID: 17438828 DOI: 10.1021/es062565m] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We have isolated novel molluskan steroid receptor transcripts orthologous to vertebrate estrogen receptors (ERs) and estrogen receptor-related receptors (ERRs) from the freshwater snail Marisa cornuarietis. Radiolabeled ligand binding analyses showed that neither recombinant receptor protein specifically bound 17beta-estradiol over the range applied (0.3-9.6 nM). These novel receptor transcripts have thus been designated mcER-like and mcERR respectively. Quantitative PCR revealed mcER-like to be expressed ubiquitously throughout a range of male and female structures studied, including neural and reproductive tissues. Highest absolute levels were seen in the male penis-sheath complex. The mcERR mRNA was also expressed ubiquitously throughout all male and female tissues analyzed here, with very low absolute transcript numbers in female accessory sex structures compared to other tissues.
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Affiliation(s)
- Richard Bannister
- Institute for the Environment, Brunel University, Uxbridge, Middlesex, UB8 3PH, UK.
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42
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Schubert M, Holland ND, Laudet V, Holland LZ. A retinoic acid-Hox hierarchy controls both anterior/posterior patterning and neuronal specification in the developing central nervous system of the cephalochordate amphioxus. Dev Biol 2006; 296:190-202. [PMID: 16750825 DOI: 10.1016/j.ydbio.2006.04.457] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2006] [Revised: 04/09/2006] [Accepted: 04/19/2006] [Indexed: 11/20/2022]
Abstract
Retinoic acid (RA) mediates both anterior/posterior patterning and neuronal specification in the vertebrate central nervous system (CNS). However, the molecular mechanisms downstream of RA are not well understood. To investigate these mechanisms, we used the invertebrate chordate amphioxus, in which the CNS, although containing only about 20,000 neurons in adults, like the vertebrate CNS, has a forebrain, midbrain, hindbrain, and spinal cord and is regionalized by RA-signaling. Here we show, first, that domains of genes with expression normally limited to diencephalon and midbrain are generally not affected by altered RA-signaling, second, that contrary to previous reports, not only Hox1, 3, and 4, but also Hox2 and Hox6 are collinearly expressed in the amphioxus CNS, and third, that collinear expression of all these Hox genes is controlled by RA-signaling. Finally, we show that Hox1 is involved in mediating both the role of RA-signaling in regionalization of the hindbrain and in specification of hindbrain motor neurons. Thus, morpholino knock-down of the single amphioxus Hox1 mimics the effects of treatments with an RA-antagonist. This analysis establishes RA-dependent regulation of collinear Hox expression as a feature common to the chordate CNS and indicates that the RA-Hox hierarchy functions both in proper anterior/posterior patterning of the developing CNS and in specification of neuronal identity.
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Affiliation(s)
- Michael Schubert
- Laboratoire de Biologie Moléculaire de la Cellule, CNRS UMR5161/INRA UMR1237/ENS Lyon, IFR128 BioSciences Lyon-Gerland, Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France
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Candiani S, Oliveri D, Parodi M, Bertini E, Pestarino M. Expression of AmphiPOU-IV in the developing neural tube and epidermal sensory neural precursors in amphioxus supports a conserved role of class IV POU genes in the sensory cells development. Dev Genes Evol 2006; 216:623-33. [PMID: 16773340 DOI: 10.1007/s00427-006-0083-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Accepted: 05/01/2006] [Indexed: 10/24/2022]
Abstract
POU genes play a prominent role in the nervous system differentiation of several organism models, and in particular, they are involved in the differentiation of sensory neurons in numerous invertebrate and vertebrate species. In the present report, cloning and expression profile of a class IV POU gene in amphioxus was assessed for understanding its role in the sensory systems development. A single class IV gene, AmphiPOU-IV was isolated from the amphioxus Branchiostoma floridae. From a phylogenetic point of view, AmphiPOU-IV appears to be strictly related to the vertebrate one, sharing a high homology ratio especially with all vertebrate POU-IV proteins Brn-3a, Brn-3b, and Brn-3c. AmphiPOU-IV was found in the most anterior neural plate and in scattered ectodermic cells on the flanks of neurula, such ectodermic cells resemble the characteristic morphology and position of AmphiCoe and AmphiTrk developing sensory cells. Later on, the expression was confined in some motoneurons at level of the PMC and in some segmental arranged motoneurons in the hindbrain. Such expression is also maintained in larvae, and a new site of AmphiPOU-IV expression was also found in rostrum and mouth edge epidermal sensory cells of the larva. In conclusion, our data suggest an evolutionary conserved role of POU-IV transcription factors in the specification and differentiation of the sensory system in both vertebrates and invertebrates and underline the importance of amphioxus as linking step between them.
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Affiliation(s)
- Simona Candiani
- Department of Biology, University of Genoa, viale Benedetto XV, 5, Genoa, 16132, Italy
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Benito-Gutiérrez E. A gene catalogue of the amphioxus nervous system. Int J Biol Sci 2006; 2:149-60. [PMID: 16763675 PMCID: PMC1474150 DOI: 10.7150/ijbs.2.149] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Accepted: 05/21/2006] [Indexed: 12/12/2022] Open
Abstract
The elaboration of extremely complex nervous systems is a major success of evolution. However, at the dawn of the post-genomic era, few data have helped yet to unravel how a nervous system develops and evolves to complexity. On the evolutionary road to vertebrates, amphioxus occupies a key position to tackle this exciting issue. Its “simple” nervous system basically consists of a dorsal nerve cord and a diffuse net of peripheral neurons, which contrasts greatly with the complexity of vertebrate nervous systems. Notwithstanding, increasing data on gene expression has faced up this simplicity by revealing a mounting level of cryptic complexity, with unexpected levels of neuronal diversity, organisation and regionalisation of the central and peripheral nervous systems. Furthermore, recent gene expression data also point to the high neurogenic potential of the epidermis of amphioxus, suggestive of a skin-brain track for the evolution of the vertebrate nervous system. Here I attempt to catalogue and synthesise current gene expression data in the amphioxus nervous system. From this global point of view, I suggest scenarios for the evolutionary origin of complex features in the vertebrate nervous system, with special emphasis on the evolutionary origin of placodes and neural crest, and postulate a pre-patterned migratory pathway of cells, which, in the epidermis, may represent an intermediate state towards the deployment of one of the most striking innovative features of vertebrates: the neural crest and its derivatives.
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Bardet PL, Laudet V, Vanacker JM. Studying non-mammalian models? Not a fool's ERRand! Trends Endocrinol Metab 2006; 17:166-71. [PMID: 16580224 PMCID: PMC1868322 DOI: 10.1016/j.tem.2006.03.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2006] [Revised: 03/07/2006] [Accepted: 03/16/2006] [Indexed: 10/24/2022]
Abstract
Through studies in mammalian model systems, the estrogen-receptor-related receptor (ERR) alpha, an orphan nuclear receptor, has been shown to interfere with estrogen signaling and might therefore be an interesting pharmaceutical target in estrogen-related diseases. ERRalpha is also involved in energy storage and consumption, and its modulation might be of relevance in the treatment of obesity and diabetes. Recent data have also been published on the effects of this receptor, as well as other members of the ERR family, in non-mammalian animal model systems. Besides indications concerning their mechanisms of action, this analysis demonstrated a role for ERRalpha in controlling cellular movements, and suggested that ERRs might be implicated in a more subtle range of processes than originally envisioned.
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Affiliation(s)
| | - Vincent Laudet
- Laboratoire de biologie moléculaire de la cellule
CNRS : UMR5161 INRAEcole Normale Supérieure de Lyon46 Allée d'Italie
69364 LYON CEDEX 07,FR
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Candiani S, Oliveri D, Parodi M, Pestarino M. Expression of AmphiNaC, a new member of the amiloride-sensitive sodium channel related to degenerins and epithelial sodium channels in amphioxus. Int J Biol Sci 2006; 2:79-86. [PMID: 16733538 PMCID: PMC1458428 DOI: 10.7150/ijbs.2.79] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Accepted: 03/22/2006] [Indexed: 11/05/2022] Open
Abstract
Degenerins and amiloride-sensitive Na+ channels form a new family of cationic ion channels (DEG/NaC). DEG/NaC family emerged as common denominator within a metazoan mechanosensory apparatus. In this study, we characterized a new member of such family in amphioxus, Branchiostoma floridae. The AmphiNaC cDNA sequence encodes a protein showing amino acid residues characteristic of DEG/NaC family, such as two hydrophobic domains surrounding a large extracellular loop that includes cystein-rich domains; nevertheless its predicted sequence is quite divergent from other family members. AmphiNaC is expressed at early larval stage in some putative sensory epidermal cells in the middle of the body and in neurons of the posterior cerebral vesicle, as well as in some ventrolateral and mediolateral neurons of the neural tube. In late larvae, AmphiNaC expression is maintained in some neurons of the neural tube, and it is expressed in putative sensory epidermal cells of rostrum and mouth. The analysis of AmphiNaC gene expression pattern suggests that it might be involved in neurotransmission and sensory modulation.
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Holland ND, Holland LZ. Stage- and tissue-specific patterns of cell division in embryonic and larval tissues of amphioxus during normal development. Evol Dev 2006; 8:142-9. [PMID: 16509893 DOI: 10.1111/j.1525-142x.2006.00085.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The distribution of dividing cells is described for embryos and larvae of amphioxus (Branchiostoma floridae) pulse labeled with bromodeoxyuridine. Because cell division is assessed for all of the developing tissues, this is the first comprehensive study of developmental cell proliferation for an animal lacking a stereotyped cell lineage. In amphioxus, cell divisions are virtually synchronous during cleavage, but become asynchronous at the blastula stage. Starting at the neurula stage, after the origin of the mesoderm, the proportion of dividing cells progressively declines in the somitic mesoderm and notochord. Other tissues, however, deviate from this pattern. For example, in the mid-neurula, there is a brief, intense burst of mitosis at the anterior end of the neural plate. Also, from the neurula through the early larval stage, all of the ectoderm cells cease dividing and develop cilia that propel the animal through the water; subsequently, in the epidermis of later larvae, mitosis resumes and the proportion of ciliated cells declines as muscular undulation gradually replaces ciliation for swimming. Finally, in the early larvae, there is a terminal arrest of cell division in three cell types that differentiate early to participate in feeding as soon as the mouth opens-namely the ciliated pharyngeal cells that produce the feeding current and the secretory cells of the club-shaped gland and endostyle that export food-trapping mucus into the pharynx. In sum, these stage- and tissue-specific changes in cell proliferation intensity illustrate how the requirements of embryonic and larval natural history can shape developmental programs.
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Affiliation(s)
- Nicholas D Holland
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093, USA.
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Holland LZ. Non-neural ectoderm is really neural: evolution of developmental patterning mechanisms in the non-neural ectoderm of chordates and the problem of sensory cell homologies. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2005; 304:304-23. [PMID: 15834938 DOI: 10.1002/jez.b.21038] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In chordates, the ectoderm is divided into the neuroectoderm and the so-called non-neural ectoderm. In spite of its name, however, the non-neural ectoderm contains numerous sensory cells. Therefore, the term "non-neural" ectoderm should be replaced by "general ectoderm." At least in amphioxus and tunicates and possibly in vertebrates as well, both the neuroectoderm and the general ectoderm are patterned anterior/posteriorly by mechanisms involving retinoic acid and Hox genes. In amphioxus and tunicates the ectodermal sensory cells, which have a wide range of ciliary and microvillar configurations, are mostly primary neurons sending axons to the CNS, although a minority lack axons. In contrast, vertebrate mechanosensory cells, called hair cells, are all secondary neurons that lack axons and have a characteristic eccentric cilium adjacent to a group of microvilli of graded lengths. It has been highly controversial whether the ectodermal sensory cells in the oral siphons of adult tunicates are homologous to vertebrate hair cells. In some species of tunicates, these cells appear to be secondary neurons, and microvillar and ciliary configurations of some of these cells approach those of vertebrate hair cells. However, none of the tunicate cells has all the characteristics of a hair cell, and there is a high degree of variation among ectodermal sensory cells within and between different species. Thus, similarities between the ectodermal sensory cells of any one species of tunicate and craniate hair cells may well represent convergent evolution rather than homology.
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Affiliation(s)
- Linda Z Holland
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, 92093-0202 USA.
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Gilland E, Baker R. Evolutionary Patterns of Cranial Nerve Efferent Nuclei in Vertebrates. BRAIN, BEHAVIOR AND EVOLUTION 2005; 66:234-54. [PMID: 16254413 DOI: 10.1159/000088128] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
All vertebrates have a similar series of rhombomeric hindbrain segments within which cranial nerve efferent nuclei are distributed in a similar rostrocaudal sequence. The registration between these two morphological patterns is reviewed here to highlight the conserved vs. variable aspects of hindbrain organization contributing to diversification of efferent sub-nuclei. Recent studies of segmental origins and migrations of branchiomotor, visceromotor and octavolateral efferent neurons revealed more segmental similarities than differences among vertebrates. Nonetheless, discrete variations exist in the origins of trigeminal, abducens and glossopharyngeal efferent nuclei. Segmental variation of the abducens nucleus remains the sole example of efferent neuronal homeosis during vertebrate hindbrain evolution. Comparison of cranial efferent segmental variations with surrounding intrinsic neurons will distinguish evolutionary changes in segment identity from lesser transformations in expression of unique neuronal types. The diversification of motoneuronal subgroups serving new muscles and functions appears to occur primarily by elaboration within and migration from already established segmental efferent pools rather than by de novo specification in different segmental locations. Identifying subtle variations in segment-specific neuronal phenotypes requires studies of cranial efferent organization within highly diverse groups such as teleosts and mammals.
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Affiliation(s)
- Edwin Gilland
- Department of Physiology and Neuroscience, New York University Medical Center, New York, N.Y., USA.
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