Synchronization of Neurogenesis and Motor Neuron Specification by Direct Coupling of bHLH and Homeodomain Transcription Factors

Inductive signaling leads to the coactivation of regulatory pathways for specifying general neuronal traits in parallel with instructions for neuronal subtype specification. Nevertheless, the mechanisms that ensure that these pathways are synchronized have not been defined. To address this, we examined how bHLH proteins Ngn2 and NeuroM controlling neurogenesis functionally converge with LIM-homeodomain (LIM-HD) factors Isl1 and Lhx3 involved in motor neuron subtype specification. We found that Ngn2 and NeuroM transcriptionally synergize with Isl1 and Lhx3 to specify motor neurons in the embryonic spinal cord and in P19 stem cells. The mechanism underlying this cooperativity is based on interactions that directly couple the activity of the bHLH and LIM-HD proteins, mediated by the adaptor protein NLI. This functional link acts to synchronize neuronal subtype specification with neurogenesis.

[1]  A. Teufel,et al.  Functional ablation of the mouse Ldb1 gene results in severe patterning defects during gastrulation , 2003, Development.

[2]  M. Rosenfeld,et al.  A family of LIM domain-associated cofactors confer transcriptional synergism between LIM and Otx homeodomain proteins. , 1997, Genes & development.

[3]  C. Goridis,et al.  The role of Phox2b in synchronizing pan-neuronal and type-specific aspects of neurogenesis. , 2002, Development.

[4]  M. Milán,et al.  Regulation of LIM homeodomain activity in vivo: a tetramer of dLDB and apterous confers activity and capacity for regulation by dLMO. , 1999, Molecular cell.

[5]  David J. Anderson,et al.  The bHLH Transcription Factors OLIG2 and OLIG1 Couple Neuronal and Glial Subtype Specification , 2002, Cell.

[6]  T. Jessell,et al.  Requirement for LIM Homeobox Gene Isl1 in Motor Neuron Generation Reveals a Motor Neuron– Dependent Step in Interneuron Differentiation , 1996, Cell.

[7]  Silvia Arber,et al.  Requirement for the Homeobox Gene Hb9 in the Consolidation of Motor Neuron Identity , 1999, Neuron.

[8]  R. Sauer,et al.  The lambda repressor contains two domains. , 1979, Proceedings of the National Academy of Sciences of the United States of America.

[9]  L. Jurata,et al.  Nuclear LIM interactor, a rhombotin and LIM homeodomain interacting protein, is expressed early in neuronal development. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[10]  W. Harris,et al.  X-ngnr-1 and Xath3 promote ectopic expression of sensory neuron markers in the neurula ectoderm and have distinct inducing properties in the retina. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[11]  T. Jessell,et al.  Coordinate Regulation of Motor Neuron Subtype Identity and Pan-Neuronal Properties by the bHLH Repressor Olig2 , 2001, Neuron.

[12]  Y. Nabeshima,et al.  The Basic Helix-Loop-Helix Factor Olig2 Is Essential for the Development of Motoneuron and Oligodendrocyte Lineages , 2002, Current Biology.

[13]  K. Tomita,et al.  Mammalian achaete–scute and atonal homologs regulate neuronal versus glial fate determination in the central nervous system , 2000, The EMBO journal.

[14]  D. Dorsett,et al.  Chip, a widely expressed chromosomal protein required for segmentation and activity of a remote wing margin enhancer in Drosophila. , 1997, Genes & development.

[15]  Thomas M. Jessell,et al.  Groucho-Mediated Transcriptional Repression Establishes Progenitor Cell Pattern and Neuronal Fate in the Ventral Neural Tube , 2001, Cell.

[16]  T. Jessell,et al.  Progression from Extrinsic to Intrinsic Signaling in Cell Fate Specification A View from the Nervous System , 1999, Cell.

[17]  S. Pfaff,et al.  The Nuclear LIM Domain Interactor NLI Mediates Homo- and Heterodimerization of LIM Domain Transcription Factors* , 1998, The Journal of Biological Chemistry.

[18]  T. Jessell,et al.  Diversity and Pattern in the Developing Spinal Cord , 1996, Science.

[19]  J. Thomas,et al.  Chip and apterous physically interact to form a functional complex during Drosophila development. , 1999, Molecular cell.

[20]  J. Funahashi,et al.  Misexpression of genes in brain vesicles by in ovo electroporation , 2000, Development, growth & differentiation.

[21]  D. Dorsett,et al.  Chip interacts with diverse homeodomain proteins and potentiates bicoid activity in vivo. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[22]  Samuel L. Pfaff,et al.  Cracking the Transcriptional Code for Cell Specification in the Neural Tube , 2001, Cell.

[23]  T. Jessell.  Neuronal specification in the spinal cord: inductive signals and transcriptional codes , 2000, Nature Reviews Genetics.

[24]  T. Jessell,et al.  Topographic organization of embryonic motor neurons defined by expression of LIM homeobox genes , 1994, Cell.

[25]  T. Becker,et al.  Multiple functions of LIM domain-binding CLIM/NLI/Ldb cofactors during zebrafish development , 2002, Mechanisms of Development.

[26]  瀬川 浩.  Functional repression of Islet-2 by disruption of complex with Ldb impairs peripheral axonal outgrowth in embryonic zebrafish , 2002 .

[27]  David J. Anderson,et al.  Divergent functions of the proneural genes Mash1 and Ngn2 in the specification of neuronal subtype identity. , 2002, Genes & development.

[28]  Samuel L. Pfaff,et al.  LIM Factor Lhx3 Contributes to the Specification of Motor Neuron and Interneuron Identity through Cell-Type-Specific Protein-Protein Interactions , 2002, Cell.

[29]  J. Olson,et al.  Generation of neurons by transient expression of neural bHLH proteins in mammalian cells. , 2000, Development.

[30]  L. Jurata,et al.  Functional analysis of the nuclear LIM domain interactor NLI , 1997, Molecular and cellular biology.

[31]  David J. Anderson,et al.  Identification of neurogenin, a Vertebrate Neuronal Determination Gene , 1996, Cell.

[32]  O. Hobert,et al.  Functions of LIM-homeobox genes. , 2000, Trends in genetics : TIG.

[33]  M. Greenberg,et al.  Neurogenin Promotes Neurogenesis and Inhibits Glial Differentiation by Independent Mechanisms , 2001, Cell.

[34]  T. Jessell,et al.  Specification of Motor Neuron Identity by the MNR2 Homeodomain Protein , 1998, Cell.

[35]  M. Nakafuku,et al.  Combinatorial Roles of Olig2 and Neurogenin2 in the Coordinated Induction of Pan-Neuronal and Subtype-Specific Properties of Motoneurons , 2001, Neuron.

[36]  H. Weintraub,et al.  Expression of achaete-scute homolog 3 in Xenopus embryos converts ectodermal cells to a neural fate. , 1994, Genes & development.

[37]  Tao Sun,et al.  Common Developmental Requirement for Olig Function Indicates a Motor Neuron/Oligodendrocyte Connection , 2002, Cell.

[38]  J. Olson,et al.  Farah, M. H. et al. Generation of neurons by transient expression of neural bHLH proteins in mammalian cells. Development 127, 693-702 , 2000 .

[39]  J. Briscoe,et al.  Specification of neuronal fates in the ventral neural tube , 2001, Current Opinion in Neurobiology.

[40]  John B. Thomas,et al.  Transcriptional mechanisms in the development of motor control , 2000, Current Opinion in Neurobiology.

[41]  T. Jessell,et al.  A Homeodomain Protein Code Specifies Progenitor Cell Identity and Neuronal Fate in the Ventral Neural Tube , 2000, Cell.

[42]  S. Pfaff,et al.  Transcriptional networks regulating neuronal identity in the developing spinal cord , 2001, Nature Neuroscience.

[43]  David J. Anderson,et al.  Two rat homologues of Drosophila achaete-scute specifically expressed in neuronal precursors , 1990, Nature.

[44]  S. Pfaff,et al.  LIM Homeodomain Factors Lhx3 and Lhx4 Assign Subtype Identities for Motor Neurons , 1998, Cell.

[45]  A. Ghysen,et al.  Deconstructing cell determination: proneural genes and neuronal identity , 1999, BioEssays : news and reviews in molecular, cellular and developmental biology.

[46]  François Guillemot,et al.  Crossregulation between Neurogenin2 and Pathways Specifying Neuronal Identity in the Spinal Cord , 2001, Neuron.

[47]  H. Weintraub,et al.  Conversion of Xenopus ectoderm into neurons by NeuroD, a basic helix-loop-helix protein. , 1995, Science.

[48]  V. Hamburger,et al.  A series of normal stages in the development of the chick embryo. 1951. , 2012, Developmental dynamics : an official publication of the American Association of Anatomists.

[49]  François Guillemot,et al.  Proneural genes and the specification of neural cell types , 2002, Nature Reviews Neuroscience.

[50]  S. Pfaff,et al.  Active Suppression of Interneuron Programs within Developing Motor Neurons Revealed by Analysis of Homeodomain Factor HB9 , 1999, Neuron.

[51]  G. Poulin,et al.  Specific Protein-Protein Interaction between Basic Helix-Loop-Helix Transcription Factors and Homeoproteins of the Pitx Family , 2000, Molecular and Cellular Biology.

[52]  P. Heitzler,et al.  Interactions between chip and the achaete/scute-daughterless heterodimers are required for pannier-driven proneural patterning. , 2000, Molecular cell.

[53]  M. Ballivet,et al.  NeuroM, a neural helix-loop-helix transcription factor, defines a new transition stage in neurogenesis. , 1997, Development.

[54]  K. Druey,et al.  A novel human homeobox gene distantly related to proboscipedia is expressed in lymphoid and pancreatic tissues. , 1994, The Journal of biological chemistry.

[55]  J. J. Breen,et al.  Interactions of the LIM-domain-binding factor Ldbl with LIM homeodomain proteins , 1996, Nature.

[56]  N. Schaeren-Wiemers,et al.  A single protocol to detect transcripts of various types and expression levels in neural tissue and cultured cells: in situ hybridization using digoxigenin-labelled cRNA probes , 1993, Histochemistry.

[57]  A. Podtelejnikov,et al.  Ssdp proteins interact with the LIM-domain-binding protein Ldb1 to regulate development , 2002, Proceedings of the National Academy of Sciences of the United States of America.