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Karaz S, Courgeon M, Lepetit H, Bruno E, Pannone R, Tarallo A, Thouzé F, Kerner P, Vervoort M, Causeret F, Pierani A, D'Onofrio G. Neuronal fate specification by the Dbx1 transcription factor is linked to the evolutionary acquisition of a novel functional domain. EvoDevo 2016; 7:18. [PMID: 27525057 PMCID: PMC4983035 DOI: 10.1186/s13227-016-0055-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 07/27/2016] [Indexed: 12/18/2022] Open
Abstract
Background Dbx1 is a homeodomain transcription factor involved in neuronal fate specification belonging to a widely conserved family among bilaterians. In mammals, Dbx1 was proposed to act as a transcriptional repressor by interacting with the Groucho corepressors to allow the specification of neurons involved in essential biological functions such as locomotion or breathing. Results Sequence alignments of Dbx1 proteins from different species allowed us to identify two conserved domains related to the Groucho-dependent Engrailed repressor domain (RD), as well as a newly described domain composed of clusterized acidic residues at the C-terminus (Cter) which is present in tetrapods but also several invertebrates. Using a heterologous luciferase assay, we showed that the two putative repressor domains behave as such in a Groucho-dependent manner, whereas the Cter does not bear any intrinsic transcriptional activity. Consistently with in vitro data, we found that both RDs are involved in cell fate specification using in vivo electroporation experiments in the chick spinal cord. Surprisingly, we show that the Cter domain is required for Dbx1 function in vivo, acting as a modulator of its repressive activity and/or imparting specificity. Conclusion Our results strongly suggest that the presence of a Cter domain among tetrapods is essential for Dbx1 to regulate neuronal diversity and, in turn, nervous system complexity. Electronic supplementary material The online version of this article (doi:10.1186/s13227-016-0055-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sonia Karaz
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Maximilien Courgeon
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Hélène Lepetit
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Eugenia Bruno
- Dept. BEOM, Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy
| | - Raimondo Pannone
- Dept. BEOM, Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy
| | - Andrea Tarallo
- Dept. BEOM, Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy
| | - France Thouzé
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Pierre Kerner
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Michel Vervoort
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Frédéric Causeret
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Alessandra Pierani
- Institut Jacques Monod, CNRS UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, 75205 Paris Cedex, France
| | - Giuseppe D'Onofrio
- Dept. BEOM, Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Naples, Italy
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Hanotel J, Bessodes N, Thélie A, Hedderich M, Parain K, Van Driessche B, Brandão KDO, Kricha S, Jorgensen MC, Grapin-Botton A, Serup P, Van Lint C, Perron M, Pieler T, Henningfeld KA, Bellefroid EJ. The Prdm13 histone methyltransferase encoding gene is a Ptf1a-Rbpj downstream target that suppresses glutamatergic and promotes GABAergic neuronal fate in the dorsal neural tube. Dev Biol 2013; 386:340-57. [PMID: 24370451 DOI: 10.1016/j.ydbio.2013.12.024] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 11/19/2013] [Accepted: 12/17/2013] [Indexed: 12/01/2022]
Abstract
The basic helix-loop-helix (bHLH) transcriptional activator Ptf1a determines inhibitory GABAergic over excitatory glutamatergic neuronal cell fate in progenitors of the vertebrate dorsal spinal cord, cerebellum and retina. In an in situ hybridization expression survey of PR domain containing genes encoding putative chromatin-remodeling zinc finger transcription factors in Xenopus embryos, we identified Prdm13 as a histone methyltransferase belonging to the Ptf1a synexpression group. Gain and loss of Ptf1a function analyses in both frog and mice indicates that Prdm13 is positively regulated by Ptf1a and likely constitutes a direct transcriptional target. We also showed that this regulation requires the formation of the Ptf1a-Rbp-j complex. Prdm13 knockdown in Xenopus embryos and in Ptf1a overexpressing ectodermal explants lead to an upregulation of Tlx3/Hox11L2, which specifies a glutamatergic lineage and a reduction of the GABAergic neuronal marker Pax2. It also leads to an upregulation of Prdm13 transcription, suggesting an autonegative regulation. Conversely, in animal caps, Prdm13 blocks the ability of the bHLH factor Neurog2 to activate Tlx3. Additional gain of function experiments in the chick neural tube confirm that Prdm13 suppresses Tlx3(+)/glutamatergic and induces Pax2(+)/GABAergic neuronal fate. Thus, Prdm13 is a novel crucial component of the Ptf1a regulatory pathway that, by modulating the transcriptional activity of bHLH factors such as Neurog2, controls the balance between GABAergic and glutamatergic neuronal fate in the dorsal and caudal part of the vertebrate neural tube.
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Affiliation(s)
- Julie Hanotel
- Laboratory of Developmental Genetics, Université Libre de Bruxelles (ULB), Institute of Molecular Biology and Medicine, and ULB Neuroscience Institute, B-6041 Gosselies, Belgium
| | - Nathalie Bessodes
- Laboratory of Developmental Genetics, Université Libre de Bruxelles (ULB), Institute of Molecular Biology and Medicine, and ULB Neuroscience Institute, B-6041 Gosselies, Belgium
| | - Aurore Thélie
- Laboratory of Developmental Genetics, Université Libre de Bruxelles (ULB), Institute of Molecular Biology and Medicine, and ULB Neuroscience Institute, B-6041 Gosselies, Belgium
| | - Marie Hedderich
- Department of Developmental Biochemistry, Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University of Goettingen, 37077 Goettingen, Germany
| | - Karine Parain
- UPR CNRS 3294 Neurobiology and Development, Université Paris Sud, 91405 Orsay Cedex, France
| | - Benoit Van Driessche
- Laboratory of Molecular Virology, Université Libre de Bruxelles (ULB), Institute of Molecular Biology and Medicine, B-6041 Gosselies, Belgium
| | - Karina De Oliveira Brandão
- Laboratory of Developmental Genetics, Université Libre de Bruxelles (ULB), Institute of Molecular Biology and Medicine, and ULB Neuroscience Institute, B-6041 Gosselies, Belgium
| | - Sadia Kricha
- Laboratory of Developmental Genetics, Université Libre de Bruxelles (ULB), Institute of Molecular Biology and Medicine, and ULB Neuroscience Institute, B-6041 Gosselies, Belgium
| | - Mette C Jorgensen
- DanStem, University of Copenhagen, 3B Blegdamsvej, DK-2200 Copenhagen N, Denmark
| | - Anne Grapin-Botton
- DanStem, University of Copenhagen, 3B Blegdamsvej, DK-2200 Copenhagen N, Denmark
| | - Palle Serup
- DanStem, University of Copenhagen, 3B Blegdamsvej, DK-2200 Copenhagen N, Denmark
| | - Carine Van Lint
- Laboratory of Molecular Virology, Université Libre de Bruxelles (ULB), Institute of Molecular Biology and Medicine, B-6041 Gosselies, Belgium
| | - Muriel Perron
- UPR CNRS 3294 Neurobiology and Development, Université Paris Sud, 91405 Orsay Cedex, France
| | - Tomas Pieler
- Department of Developmental Biochemistry, Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University of Goettingen, 37077 Goettingen, Germany
| | - Kristine A Henningfeld
- Department of Developmental Biochemistry, Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), University of Goettingen, 37077 Goettingen, Germany
| | - Eric J Bellefroid
- Laboratory of Developmental Genetics, Université Libre de Bruxelles (ULB), Institute of Molecular Biology and Medicine, and ULB Neuroscience Institute, B-6041 Gosselies, Belgium.
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3
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Posnien N, Koniszewski NDB, Hein HJ, Bucher G. Candidate gene screen in the red flour beetle Tribolium reveals six3 as ancient regulator of anterior median head and central complex development. PLoS Genet 2011; 7:e1002416. [PMID: 22216011 PMCID: PMC3245309 DOI: 10.1371/journal.pgen.1002416] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 10/13/2011] [Indexed: 11/19/2022] Open
Abstract
Several highly conserved genes play a role in anterior neural plate patterning of vertebrates and in head and brain patterning of insects. However, head involution in Drosophila has impeded a systematic identification of genes required for insect head formation. Therefore, we use the red flour beetle Tribolium castaneum in order to comprehensively test the function of orthologs of vertebrate neural plate patterning genes for a function in insect head development. RNAi analysis reveals that most of these genes are indeed required for insect head capsule patterning, and we also identified several genes that had not been implicated in this process before. Furthermore, we show that Tc-six3/optix acts upstream of Tc-wingless, Tc-orthodenticle1, and Tc-eyeless to control anterior median development. Finally, we demonstrate that Tc-six3/optix is the first gene known to be required for the embryonic formation of the central complex, a midline-spanning brain part connected to the neuroendocrine pars intercerebralis. These functions are very likely conserved among bilaterians since vertebrate six3 is required for neuroendocrine and median brain development with certain mutations leading to holoprosencephaly.
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Affiliation(s)
- Nico Posnien
- Center for Molecular Physiology of the Brain (CMPB), Göttingen Center of Molecular Biology, Caspari-Haus, Georg-August-University Göttingen, Göttingen, Germany
- School of Life Sciences, Oxford Brookes University, Oxford, United Kingdom
| | - Nikolaus Dieter Bernhard Koniszewski
- Center for Molecular Physiology of the Brain (CMPB), Göttingen Center of Molecular Biology, Caspari-Haus, Georg-August-University Göttingen, Göttingen, Germany
| | | | - Gregor Bucher
- Center for Molecular Physiology of the Brain (CMPB), Göttingen Center of Molecular Biology, Caspari-Haus, Georg-August-University Göttingen, Göttingen, Germany
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4
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Ma P, Zhao S, Zeng W, Yang Q, Li C, Lv X, Zhou Q, Mao B. Xenopus Dbx2 is involved in primary neurogenesis and early neural plate patterning. Biochem Biophys Res Commun 2011; 412:170-4. [PMID: 21806971 DOI: 10.1016/j.bbrc.2011.07.068] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 07/18/2011] [Indexed: 12/19/2022]
Abstract
The evolutionarily conserved Dbx homeodomain-containing proteins play important roles in the development of vertebrate central nervous system. In mouse, Dbx and Nkx6 have been suggested to be cross-repressive partners involved in the patterning of ventral neural tube. Here, we have isolated Xenopus Dbx2 and studied its developmental expression and function during neural development. Like XDbx1, from mid-neurula stage on, XDbx2 is expressed in stripes between the primary motoneurons and interneurons. At the tailbud stages, it is detected in the middle region of the neural tube. XDbx2 acts as a transcriptional repressor in vitro and over-expression of XDbx2 inhibits primary neurogenesis in Xenopus embryos. Over-expression of XDbx genes represses the expression of XNkx6.2 and vise versa. Knockdown of either XDbx1, XDbx2 or both by specific morpholinos induces lateral expansion of XNkx6.2 expression domains. These data reveal conserved roles for Dbx in primary neurogenesis and dorsoventral neural patterning in Xenopus.
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Affiliation(s)
- Pengcheng Ma
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, China
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5
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Winterbottom EF, Ramsbottom SA, Isaacs HV. Gsx transcription factors repress Iroquois gene expression. Dev Dyn 2011; 240:1422-9. [DOI: 10.1002/dvdy.22648] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/27/2011] [Indexed: 11/10/2022] Open
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6
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Morona R, Ferran JL, Puelles L, González A. Embryonic genoarchitecture of the pretectum in Xenopus laevis: A conserved pattern in tetrapods. J Comp Neurol 2011; 519:1024-50. [DOI: 10.1002/cne.22548] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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7
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Dichmann DS, Harland RM. Nkx6 genes pattern the frog neural plate and Nkx6.1 is necessary for motoneuron axon projection. Dev Biol 2010; 349:378-86. [PMID: 21035438 DOI: 10.1016/j.ydbio.2010.10.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 10/20/2010] [Accepted: 10/20/2010] [Indexed: 12/28/2022]
Abstract
Neuronal subtypes originate from an undifferentiated neural epithelium that is progressively divided into progenitor domains by homeodomain transcription factors such as members of the Nkx family. Here we report the functional analysis of Nkx6.1 and Nkx6.2 in Xenopus. While Nkx6.2 is expressed early in a large region of the medial neural plate, Nkx6.1 is restricted to a region overlapping with the region of motor neuron formation. By mRNA injection we show that both can inhibit primary neurogenesis as well as expression of intermediate neural plate markers. However, they do not form auto-regulatory loops and fail to induce ectopic motor neurons as they do in the chick. Using morpholino-mediated knockdown in Xenopus laevis and Xenopus tropicalis we show that Nkx6.1 knockdown results in paralyzed tadpoles. Using DiI labeling and immunohistochemistry we show that the underlying mechanism is a failure of spinal motor neurons to extend axons to their targets. Analysis of neural pattern reveals that ventral Lhx3+ and Pax2+ interneurons are dependent on Nkx6.1 function, but overall neural patterning is not. This study illustrates that while important aspects of Nkx6 gene function are conserved in vertebrate neural patterning, others are not.
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Affiliation(s)
- Darwin S Dichmann
- Department of Molecular & Cell Biology, Center for Integrative Genomics, University of California, Berkeley, 571 Life Sciences Addition, #3200, Berkeley, CA 94720-3200, USA
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8
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Winterbottom EF, Illes JC, Faas L, Isaacs HV. Conserved and novel roles for the Gsh2 transcription factor in primary neurogenesis. Development 2010; 137:2623-31. [DOI: 10.1242/dev.047159] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The Gsx genes encode members of the ParaHox family of homeodomain transcription factors, which are expressed in the developing central nervous system in members of all major groups of bilaterians. The Gsx genes in Xenopus show similar patterns of expression to their mammalian homologues during late development. However, they are also expressed from early neurula stages in an intermediate region of the open neural plate where primary interneurons form. The Gsx homologue in the protostome Drosophila is expressed in a corresponding intermediate region of the embryonic neuroectoderm, and is essential for the correct specification of the neuroblasts that arise from it, suggesting that Gsx genes may have played a role in intermediate neural specification in the last common bilaterian ancestor. Here, we show that manipulation of Gsx function disrupts the differentiation of primary interneurons. We demonstrate that, despite their similar expression patterns, the uni-directional system of interactions between homeodomain transcription factors from the Msx, Nkx and Gsx families in the Drosophila neuroectoderm is not conserved between their homologues in the Xenopus open neural plate. Finally, we report the identification of Dbx1 as a direct target of Gsh2-mediated transcriptional repression, and show that a series of cross-repressive interactions, reminiscent of those that exist in the amniote neural tube, act between Gsx, Dbx and Nkx transcription factors to pattern the medial aspect of the central nervous system at open neural plate stages in Xenopus.
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Affiliation(s)
| | - Jean C. Illes
- Area 11, Department of Biology, University of York, York YO10 5YW, UK
| | - Laura Faas
- Area 11, Department of Biology, University of York, York YO10 5YW, UK
| | - Harry V. Isaacs
- Area 11, Department of Biology, University of York, York YO10 5YW, UK
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9
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Nieber F, Pieler T, Henningfeld KA. Comparative expression analysis of the neurogenins in Xenopus tropicalis and Xenopus laevis. Dev Dyn 2009; 238:451-8. [DOI: 10.1002/dvdy.21845] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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10
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Gribble SL, Nikolaus OB, Dorsky RI. Regulation and function of Dbx genes in the zebrafish spinal cord. Dev Dyn 2008; 236:3472-83. [PMID: 17994542 DOI: 10.1002/dvdy.21367] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Dbx homeodomain proteins are important for spinal cord dorsal/ventral patterning and the production of multiple spinal cord cell types. We have examined the regulation and function of Dbx genes in the zebrafish. We report that Hedgehog signaling is not required for the induction or maintenance of these genes; in the absence of Hedgehog signaling, dbx1a/1b/2 are expanded ventrally with concomitant increases in postmitotic neurons that differentiate from this domain. Also, we find that retinoic acid signaling is not required for the induction of Dbx expression. Furthermore, we are the first to report that knockdown of Dbx1 function causes a dorsal expansion of nkx6.2, which is thought to be the cross-repressive partner of Dbx1 in mouse. Our data confirm that the dbx1a/1b/2 domain in zebrafish spinal cord development behaves similarly to amniotes, while extending knowledge of Dbx1 function in spinal cord patterning.
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Affiliation(s)
- Suzanna L Gribble
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah 84132-3401, USA
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11
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Talikka M, Stefani G, Brivanlou AH, Zimmerman K. Characterization of Xenopus Phox2a and Phox2b defines expression domains within the embryonic nervous system and early heart field. Gene Expr Patterns 2005; 4:601-7. [PMID: 15261839 DOI: 10.1016/j.modgep.2004.01.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2003] [Revised: 01/12/2004] [Accepted: 01/16/2004] [Indexed: 11/25/2022]
Abstract
The closely related homeodomain containing genes, Phox2a and Phox2b, are essential for neuronal specification and differentiation within discrete subsets of neurons during vertebrate embryogenesis. We have isolated Xenopus Phox2 homologs, termed Xphox2a and Xphox2b, and characterized their expression during early development. In addition, we have characterized a Phox2a splice variant, termed Xphox2a.2, which lacks homeo- and C-terminal protein coding domains. Xphox2a, Xphox2a.2 and Xphox2b transcripts are expressed in dynamic temporal and regional patterns during nervous system development. The expression of Xphox2a and Xphox2b is only partially overlapping and includes cranial motor and interneuron populations as well as peripheral sympathetic and cranial ganglion neurons, sites linked to Phox2 expression in other species. In addition, we have identified an early domain of Xphox2a and subsequent Xphox2b expression in ventral regions of the embryo, within the developing heart field. XPhox2 expression within this domain is preceded by the gastrula-stage expression of the proneural basic helix-loop-helix transcription factor, Xash1, pointing to a new region of action for this group transcription factors during vertebrate development.
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Affiliation(s)
- Marja Talikka
- Laboratory of Developmental Neurobiology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
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12
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Bally-Cuif L, Hammerschmidt M. Induction and patterning of neuronal development, and its connection to cell cycle control. Curr Opin Neurobiol 2003; 13:16-25. [PMID: 12593978 DOI: 10.1016/s0959-4388(03)00015-1] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Nervous tissue is derived from early embryonic ectoderm, which also gives rise to epidermal derivatives such as skin. The progression from naive ectoderm to differentiated postmitotic neurons involves multiple steps, two of which are crucial in shaping the final neurogenesis pattern. First, is the identification of the neural plate by the process of neural induction. Second, is the selection of a restricted number of sites within the neural plate where neurogenesis, the process leading to final differentiation of neural precursors, is initiated. Recent findings point to the existence of positive inducers of the neural state, whereas, neurogenesis initiation sites appear to be largely defined by inhibition. However, both neural induction and the initiation of neurogenesis appear to be connected to cell cycle control systems that govern whether stem cell maintenance and cell proliferation, or cell specification and differentiation, take place.
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Affiliation(s)
- Laure Bally-Cuif
- Zebrafish Neurogenetics Junior Research Group, Institute of Virology, Technical University-Munich, Trogerstrasse 4b, D-81675, Munich, Germany.
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13
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Talikka M, Perez SE, Zimmerman K. Distinct patterns of downstream target activation are specified by the helix-loop-helix domain of proneural basic helix-loop-helix transcription factors. Dev Biol 2002; 247:137-48. [PMID: 12074558 DOI: 10.1006/dbio.2002.0677] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Both gain- and loss-of-function analyses indicate that proneural basic/helix-loop-helix (bHLH) proteins direct not only general aspects of neuronal differentiation but also specific aspects of neuronal identity within neural progenitors. In order to better understand the function of this family of transcription factors, we have used hormone-inducible fusion constructs to assay temporal patterns of downstream target regulation in response to proneural bHLH overexpression. In these studies, we have compared two distantly related Xenopus proneural bHLH genes, Xash1 and XNgnr1. Our findings indicate that both Xash1 and XNgnr1 induce expression of the general neuronal differentiation marker, N-tubulin, with a similar time course in animal cap progenitor populations. In contrast, these genes each induce distinct patterns of early downstream target expression. Both genes induce expression of the HLH-containing gene, Xcoe2, at early time points, but only XNgnr1 induces early expression of the bHLH genes, Xath3 and XNeuroD. Structure:function analyses indicate that the distinct pattern of XNgnr1-induced downstream target activation is linked to the XNgnr1 HLH domain, demonstrating a novel role for this domain in mediating the differential function of individual members of the proneural bHLH gene family.
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Affiliation(s)
- Marja Talikka
- Laboratory of Developmental Neurobiology, The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
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14
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Chalmers AD, Welchman D, Papalopulu N. Intrinsic differences between the superficial and deep layers of the Xenopus ectoderm control primary neuronal differentiation. Dev Cell 2002; 2:171-82. [PMID: 11832243 DOI: 10.1016/s1534-5807(02)00113-2] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In Xenopus, primary neurons differentiate early, in the deep layer of the neuroectoderm. In contrast, the neural precursors of the superficial layer continue to proliferate. We report that superficial layer precursors differ from deep layer precursors in that they are refractory to the neuronal-promoting activity of bHLH genes, dominant-negative X-Delta-1, FGF-8, or signals from the organizer. In this system, neuronal differentiation is guided by an early established, intrinsic, cell-autonomous difference in the competence of the precursor cells to differentiate. This difference may be controlled in part by ESR6e, a bHLH gene of the Enhancer-of-split family, which is expressed in the superficial layer of the late blastula and when expressed ectopically suppresses primary neurogenesis in the deep layer.
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Affiliation(s)
- Andrew D Chalmers
- Wellcome/CRC Institute, Tennis Court Road, CB2 1QR, Cambridge, United Kingdom
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15
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Pierani A, Moran-Rivard L, Sunshine MJ, Littman DR, Goulding M, Jessell TM. Control of interneuron fate in the developing spinal cord by the progenitor homeodomain protein Dbx1. Neuron 2001; 29:367-84. [PMID: 11239429 DOI: 10.1016/s0896-6273(01)00212-4] [Citation(s) in RCA: 291] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Spinal interneurons help to coordinate motor behavior. During spinal cord development, distinct classes of interneurons are generated from progenitor cells located at different positions within the ventral neural tube. V0 and V1 interneurons derive from adjacent progenitor domains that are distinguished by expression of the homeodomain proteins Dbx1 and Dbx2. The spatially restricted expression of Dbx1 has a critical role in establishing the distinction in V0 and V1 neuronal fate. In Dbx1 mutant mice, neural progenitors fail to generate V0 neurons and instead give rise to interneurons that express many characteristics of V1 neurons-their transcription factor profile, neurotransmitter phenotype, migratory pattern, and aspects of their axonal trajectory. Thus, a single progenitor homeodomain transcription factor coordinates many of the differentiated properties of one class of interneurons generated in the ventral spinal cord.
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Affiliation(s)
- A Pierani
- Howard Hughes Medical Institute, Department of Biochemistry and, Molecular Biophysics, Center for Neurobiology and Behavior, Columbia University, New York, NY 10032, USA
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