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Jongbloets BC, Lemstra S, Schellino R, Broekhoven MH, Parkash J, Hellemons AJCGM, Mao T, Giacobini P, van Praag H, De Marchis S, Ramakers GMJ, Pasterkamp RJ. Stage-specific functions of Semaphorin7A during adult hippocampal neurogenesis rely on distinct receptors. Nat Commun 2017; 8:14666. [PMID: 28281529 PMCID: PMC5353663 DOI: 10.1038/ncomms14666] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 01/23/2017] [Indexed: 02/06/2023] Open
Abstract
The guidance protein Semaphorin7A (Sema7A) is required for the proper development of the immune and nervous systems. Despite strong expression in the mature brain, the role of Sema7A in the adult remains poorly defined. Here we show that Sema7A utilizes different cell surface receptors to control the proliferation and differentiation of neural progenitors in the adult hippocampal dentate gyrus (DG), one of the select regions of the mature brain where neurogenesis occurs. PlexinC1 is selectively expressed in early neural progenitors in the adult mouse DG and mediates the inhibitory effects of Sema7A on progenitor proliferation. Subsequently, during differentiation of adult-born DG granule cells, Sema7A promotes dendrite growth, complexity and spine development through β1-subunit-containing integrin receptors. Our data identify Sema7A as a key regulator of adult hippocampal neurogenesis, providing an example of how differential receptor usage spatiotemporally controls and diversifies the effects of guidance cues in the adult brain.
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Affiliation(s)
- Bart C. Jongbloets
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
| | - Suzanne Lemstra
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
| | - Roberta Schellino
- Dipartimento di Scienze della Vita e Biologia dei Sistemi and Neuroscience Institute Cavalieri Ottolenghi, University of Torino, 10100 Torino, Italy
| | - Mark H. Broekhoven
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
| | - Jyoti Parkash
- Centre for Animal Sciences, School of Basic and Applied Sciences, Central University Punjab, City Campus, Mansa Road, Bathinda 151001, India
| | - Anita J. C. G. M. Hellemons
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
| | - Tianyi Mao
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239, USA
| | - Paolo Giacobini
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Centre, U1172, 59045 Lille, France
- University of Lille, 59045 Lille, France
| | - Henriette van Praag
- Neuroplasticity and Behavior Unit, Laboratory of Neurosciences, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224, USA
| | - Silvia De Marchis
- Dipartimento di Scienze della Vita e Biologia dei Sistemi and Neuroscience Institute Cavalieri Ottolenghi, University of Torino, 10100 Torino, Italy
| | - Geert M. J. Ramakers
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
| | - R. Jeroen Pasterkamp
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands
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van Erp S, van den Heuvel DMA, Fujita Y, Robinson RA, Hellemons AJCGM, Adolfs Y, Van Battum EY, Blokhuis AM, Kuijpers M, Demmers JAA, Hedman H, Hoogenraad CC, Siebold C, Yamashita T, Pasterkamp RJ. Lrig2 Negatively Regulates Ectodomain Shedding of Axon Guidance Receptors by ADAM Proteases. Dev Cell 2015; 35:537-552. [PMID: 26651291 DOI: 10.1016/j.devcel.2015.11.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 10/02/2015] [Accepted: 11/09/2015] [Indexed: 12/11/2022]
Abstract
Many guidance receptors are proteolytically cleaved by membrane-associated metalloproteases of the ADAM family, leading to the shedding of their ectodomains. Ectodomain shedding is crucial for receptor signaling and function, but how this process is controlled in neurons remains poorly understood. Here, we show that the transmembrane protein Lrig2 negatively regulates ADAM-mediated guidance receptor proteolysis in neurons. Lrig2 binds Neogenin, a receptor for repulsive guidance molecules (RGMs), and prevents premature Neogenin shedding by ADAM17 (TACE). RGMa reduces Lrig2-Neogenin interactions, providing ADAM17 access to Neogenin and allowing this protease to induce ectodomain shedding. Regulation of ADAM17-mediated Neogenin cleavage by Lrig2 is required for neurite growth inhibition by RGMa in vitro and for cortical neuron migration in vivo. Furthermore, knockdown of Lrig2 significantly improves CNS axon regeneration. Together, our data identify a unique ligand-gated mechanism to control receptor shedding by ADAMs and reveal functions for Lrigs in neuron migration and regenerative failure.
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Affiliation(s)
- Susan van Erp
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands
| | - Dianne M A van den Heuvel
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands
| | - Yuki Fujita
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University 2-2, Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Ross A Robinson
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Anita J C G M Hellemons
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands
| | - Youri Adolfs
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands
| | - Eljo Y Van Battum
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands
| | - Anna M Blokhuis
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands
| | - Marijn Kuijpers
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Jeroen A A Demmers
- Proteomics Centre and Department of Cell Biology, Erasmus University Medical Centre, Dr Molewaterplein 50, 3015 GE Rotterdam, the Netherlands
| | - Håkan Hedman
- Oncology Research Laboratory, Department of Radiation Sciences, Umeå University, 90187 Umeå, Sweden
| | - Casper C Hoogenraad
- Cell Biology, Faculty of Science, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Christian Siebold
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Toshihide Yamashita
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University 2-2, Yamadaoka, Suita, Osaka 565-0871, Japan
| | - R Jeroen Pasterkamp
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584 CG Utrecht, the Netherlands.
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Burbach JPH, Hellemons AJCGM, Grant P, Pant HC. The homeodomain transcription factor Phox2 in the stellate ganglion of the squid Loligo pealei. Biol Open 2015; 4:954-60. [PMID: 26116657 PMCID: PMC4542286 DOI: 10.1242/bio.012476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Homeodomain transcription factors regulate development of embryos and cellular physiology in adult systems. Paired-type homeodomain genes constitute a subclass that has been particularly implicated in establishment of neuronal identity in the mammalian nervous system. We isolated fragments of eight homeodomain genes of this subclass expressed in the stellate ganglion of the North Atlantic long finned squid Loligo pealei (lp) [Note: Loligo pealei has been officially renamed Doryteuthis pealei. For reasons of uniformity and clarity Loligo pealei (lp) is used here]. Of the most abundant ones, we cloned a full length cDNA which encoded the squid ortholog of the paired-type homeodomain proteins Phox2a/b. The homology of lpPhox2 to invertebrate and mammalian Phox2 was limited to the homeodomain. In contrast to mouse Phox2b, lpPhox2 was unable to transactivate the dopamine beta-hydroxylase (DBH) promoter in a heterologous mammalian transfection system. In vivo, lpPhox2 was expressed in the developing stellate ganglion of stage 27 squid embryos and continued to be expressed in the adult stellate neurons where expression was confined to the giant fiber lobe containing the neurons that form the giant axons. The expression of lpPhox was similarly timed and distributed as the Fmrf gene. Furthermore, the Fmrf upstream region contained putative Phox2a/b binding sites. These results suggest a role of lpPhox2 in the developmental specification of neuronal identity and regulation of neurons of the squid giant axon.
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Affiliation(s)
- J. Peter H. Burbach
- Brain Center Rudolf Magnus, Department of Translational Neuroscience, University Medical Center Utrecht, Utrecht University, Utrecht 3584CG, The Netherlands
- Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Anita J. C. G. M. Hellemons
- Brain Center Rudolf Magnus, Department of Translational Neuroscience, University Medical Center Utrecht, Utrecht University, Utrecht 3584CG, The Netherlands
- Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Philip Grant
- Marine Biological Laboratory, Woods Hole, MA 02543, USA
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
| | - Harish C. Pant
- Marine Biological Laboratory, Woods Hole, MA 02543, USA
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA
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Burbach JPH, Grant P, Hellemons AJCGM, Degiorgis JA, Li KW, Pant HC. Differential expression of the FMRF gene in adult and hatchling stellate ganglia of the squid Loligo pealei. Biol Open 2014; 3:50-8. [PMID: 24326188 PMCID: PMC3892160 DOI: 10.1242/bio.20136890] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The giant fiber system of the squid Loligo pealei mediates the escape response and is an important neurobiological model. Here, we identified an abundant transcript in the stellate ganglion (SG) that encodes a FMRFamide precursor, and characterized FMRFamide and FI/LRF-amide peptides. To determine whether FMRFamide plays a role in the adult and hatchling giant fiber system, we studied the expression of the Fmrf gene and FMRFamide peptides. In stage 29 embryos and stage 30 hatchlings, Ffmr transcripts and FMRFamide peptide were low to undetectable in the SG, in contrast to groups of neurons intensely expressing the Fmrf gene in several brain lobes, including those that innervate the SG. In the adult SG the Fmrf gene was highly expressed, but the FMRFamide peptide was in low abundance. Intense staining for FMRFamide in the adult SG was confined to microneurons and fibers in the neuropil and to small fibers surrounding giant axons in stellar nerves. This shows that the Fmrf gene in the SG is strongly regulated post-hatching, and suggests that the FMRFamide precursor is incompletely processed in the adult SG. The data suggest that the SG only employs the Fmrf gene post-hatching and restricts the biosynthesis of FMRFamide, demonstrating that this peptide is not a major transmitter of the giant fiber system. This contrasts with brain lobes that engage FMRFamide embryonically as a regulatory peptide in multiple neuronal systems, including the afferent fibers that innervate the SG. The biological significance of these mechanisms may be to generate diversity within Fmrf-expressing systems in cephalopods.
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Affiliation(s)
- J Peter H Burbach
- Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, 3584CG Utrecht, The Netherlands
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Kolk SM, Gunput RAF, Tran TS, van den Heuvel DMA, Prasad AA, Hellemons AJCGM, Adolfs Y, Ginty DD, Kolodkin AL, Burbach JPH, Smidt MP, Pasterkamp RJ. Semaphorin 3F is a bifunctional guidance cue for dopaminergic axons and controls their fasciculation, channeling, rostral growth, and intracortical targeting. J Neurosci 2009; 29:12542-57. [PMID: 19812329 PMCID: PMC3097132 DOI: 10.1523/jneurosci.2521-09.2009] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2009] [Revised: 08/10/2009] [Accepted: 09/01/2009] [Indexed: 01/22/2023] Open
Abstract
Dopaminergic neurons in the mesodiencephalon (mdDA neurons) make precise synaptic connections with targets in the forebrain via the mesostriatal, mesolimbic, and mesoprefrontal pathways. Because of the functional importance of these remarkably complex ascending axon pathways and their implication in human disease, the mechanisms underlying the development of these connections are of considerable interest. Despite extensive in vitro studies, the molecular determinants that ensure the perfect formation of these pathways in vivo remain mostly unknown. Here, we determine the embryonic origin and ontogeny of the mouse mesoprefrontal pathway and use these data to reveal an unexpected requirement for semaphorin 3F (Sema3F) and its receptor neuropilin-2 (Npn-2) during mdDA pathway development using tissue culture approaches and analysis of sema3F(-/-), npn-2(-/-), and npn-2(-/-);TH-Cre mice. We show that Sema3F is a bifunctional guidance cue for mdDA axons, some of which have the remarkable ability to regulate their responsiveness to Sema3F as they develop. During early developmental stages, Sema3F chemorepulsion controls previously uncharacterized aspects of mdDA pathway development through both Npn-2-dependent (axon fasciculation and channeling) and Npn-2-independent (rostral growth) mechanisms. Later on, chemoattraction mediated by Sema3F and Npn-2 is required to orient mdDA axon projections in the cortical plate of the medial prefrontal cortex. This latter finding demonstrates that regulation of axon orientation in the target field occurs by chemoattractive mechanisms, and this is likely to also apply to other neural systems. In all, this study provides a framework for additional dissection of the molecular basis of mdDA pathway development and disease.
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Affiliation(s)
- Sharon M. Kolk
- Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands, and
| | - Rou-Afza F. Gunput
- Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands, and
| | - Tracy S. Tran
- The Solomon H. Snyder Department of Neuroscience and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Dianne M. A. van den Heuvel
- Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands, and
| | - Asheeta A. Prasad
- Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands, and
| | - Anita J. C. G. M. Hellemons
- Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands, and
| | - Youri Adolfs
- Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands, and
| | - David D. Ginty
- The Solomon H. Snyder Department of Neuroscience and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Alex L. Kolodkin
- The Solomon H. Snyder Department of Neuroscience and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - J. Peter H. Burbach
- Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands, and
| | - Marten P. Smidt
- Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands, and
| | - R. Jeroen Pasterkamp
- Department of Neuroscience and Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, 3584 CG Utrecht, The Netherlands, and
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Smidt MP, Smits SM, Bouwmeester H, Hamers FPT, van der Linden AJA, Hellemons AJCGM, Graw J, Burbach JPH. Early developmental failure of substantia nigra dopamine neurons in mice lacking the homeodomain gene Pitx3. Development 2004; 131:1145-55. [PMID: 14973278 DOI: 10.1242/dev.01022] [Citation(s) in RCA: 245] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The mesencephalic dopamine (mesDA) system is involved in the control of movement and behavior. The expression of Pitx3 in the brain is restricted to the mesDA system and the gene is induced relatively late, at E11.5, a time when tyrosine hydroxylase (Th) gene expression is initiated. We show here that, in the Pitx3-deficient aphakia (ak) mouse mutant, the mesDA system is malformed. Owing to the developmental failure of mesDA neurons in the lateral field of the midbrain, mesDA neurons are not found in the SNc and the projections to the caudate putamen are selectively lost. However, Pitx3 is expressed in all mesDA neurons in control animals. Therefore, mesDA neurons react specifically to the loss of Pitx3. Defects of motor control where not seen in the ak mice, suggesting that other neuronal systems compensate for the absence of the nigrostriatal pathway. However, an overall lower activity was observed. The results suggest that Pitx3 is specifically required for the formation of the SNc subfield at the onset of dopaminergic neuron differentiation.
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Affiliation(s)
- Marten P Smidt
- Rudolf Magnus Institute of Neuroscience, Department of Pharmacology and Anatomy, University Medical Center, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
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Kromkamp M, Uylings HBM, Smidt MP, Hellemons AJCGM, Burbach JPH, Kahn RS. Decreased thalamic expression of the homeobox gene DLX1 in psychosis. Arch Gen Psychiatry 2003; 60:869-74. [PMID: 12963668 DOI: 10.1001/archpsyc.60.9.869] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
CONTEXT A shared vulnerability to develop psychosis can be related to abnormalities in thalamic circuits in schizophrenia and bipolar disorder and could be a genetic link between these disorders. Homeobox genes involved in development and differentiation of the brain could play an important role in these disorders. OBJECTIVE To determine whether patients with schizophrenia and bipolar disorder have different thalamic expression patterns of 2 homeobox genes, DLX1 and SHOX2 (alias OG12X or SHOT) compared with psychiatric and nonpsychiatric control subjects. DESIGN Postmortem sections containing the thalamic mediodorsal nucleus were subjected to in situ hybridization with mouse Dlx1 and human SHOX2 RNA probes. The number of both DLX1- and SHOX2-positive neurons relative to Nissl-stained neurons was estimated in systematic randomly sampled volume probes. Patients Fifteen patients with schizophrenia, 15 with bipolar disorder with or without history of psychosis, 15 with major depressive disorder, and 15 nonpsychiatric controls from the Stanley Foundation Brain Bank. MAIN OUTCOME MEASURE Relative numbers of DLX1- and SHOX2-positive neurons in patients with schizophrenia and bipolar disorder with history of psychosis compared with psychiatric and nonpsychiatric controls. RESULTS Patients with a history of psychosis showed significantly decreased relative numbers of DLX1-positive neurons compared with patients without history of psychosis and nonpsychiatric controls (P =.02), whereas no differences could be found in relative numbers of SHOX2-positive neurons (P>.15). Results were obtained blind to diagnosis, symptoms, or any other variable except hemisphere. CONCLUSION Decreased thalamic expression of DLX1 in schizophrenia and bipolar disorder with psychosis suggests shared genetic deficits in expression of this homeobox gene.
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Affiliation(s)
- Marjan Kromkamp
- Department of Pharmacology, Rudolf Magnus Institute for Neurosciences, University Medical Center, Utrecht, The Netherlands
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van der Zwaag B, Hellemons AJCGM, Leenders WPJ, Burbach JPH, Brunner HG, Padberg GW, Van Bokhoven H. PLEXIN-D1, a novel plexin family member, is expressed in vascular endothelium and the central nervous system during mouse embryogenesis. Dev Dyn 2002; 225:336-43. [PMID: 12412018 DOI: 10.1002/dvdy.10159] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The genetic defect in Möbius syndrome 2 (MBS2, MIM 601471), a dominantly inherited disorder characterised by paralysis of the facial nerve, is situated at chromosome 3q21-q22. We characterised the cDNA and predicted protein, and examined the expression pattern during mouse embryogenesis of a positional candidate gene, PLEXIN-D1 (PLXND1). The cDNA for PLXND1 is 7095 base pairs in length, coding for a predicted protein of 1925 amino acids. The protein features all known domains of plexin family members, with the exception of the third Met-related sequence. Northern analysis revealed a very low expression of PLXND1 in adult mouse and adult human tissues. To investigate the expression of PlxnD1 during embryogenesis, RNA in situ hybridisation was performed on mouse embryos from various stages. This investigation revealed expression of PlxnD1 in cells from the central nervous system (CNS) and in vascular endothelium. Early expression in the CNS is located in the ganglia, cortical plate of the cortex, and striatum. At later embryologic stages, neural expression was also seen in the external granular layer of the cerebellum and several nerve nuclei. The expression in the vascular system resides solely in the endothelial cells of developing blood vessels. Based on our results, we suggest that this expression of a member of the plexin family in vascular endothelium could point toward a role in embryonic vasculogenesis.
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Affiliation(s)
- Bert van der Zwaag
- Department of Neurology, University Medical Centre Nijmegen, Nijmegen, The Netherlands
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