Combinatorial signalling controls Neurogenin2 expression at the onset of spinal neurogenesis.
A central issue during embryonic development is to define how different signals cooperate in generating unique cell types. To address this issue, we focused on the function and the regulation of the proneural gene Neurogenin2 (Neurog2) during early mouse spinal neurogenesis. We showed that Neurog2 is first expressed in cells within the neural plate anterior to the node from the 5 somite-stage. The analysis of Neurog2 mutants established a role for this gene in triggering neural differentiation during spinal cord elongation. We identified a 798 base pair enhancer element (Neurog2-798) upstream of the Neurog2 coding sequence that directs the early caudal expression of Neurog2. Embryo culture experiments showed that Retinoic Acid (RA), Sonic hedgehog (Shh) and Fibroblast Growth Factor signals act in concert on this enhancer to control the spatial and temporal induction of Neurog2. We further demonstrated by transgenesis that two RA response elements and a Gli binding site within the Neurog2-798 element are absolutely required for its activity, strongly suggesting that the regulation of Neurog2 early expression by RA and Shh signals is direct. Our data thus support a model where signal integration at the level of a single enhancer constitutes a key mechanism to control the onset of neurogenesis.
Ribes
Vanessa
V
Institut de Génétique et de Biologie Moléculaire et Cellulaire, Inserm U 596, CNRS UMR 7104, Université Louis Pasteur, 1 rue Laurent Friès, Illkirch, BP 10142 F-67400, France.
Stutzmann
Fanny
F
Bianchetti
Laurent
L
Guillemot
François
F
Dollé
Pascal
P
Le Roux
Isabelle
I
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D005346:Fibroblast Growth Factors / Q000378:metabolism; D005697:Galactosides; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D053823:Hedgehog Proteins / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007211:Indoles; D051379:Mice; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009841:Oligonucleotides / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology*; D013116:Spinal Cord / Q000196:embryology*; D014212:Tretinoin / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D005346:Fibroblast Growth Factors; D005697:Galactosides; D053823:Hedgehog Proteins; D007211:Indoles; D009419:Nerve Tissue Proteins; D009841:Oligonucleotides; D014212:Tretinoin; C102938:Neurog2 protein, mouse; C465570:Shh protein, mouse; C044888:5-bromo-4-chloro-3-indolyl beta-galactoside