Ascl1 and Neurog2 form novel complexes and regulate Delta-like3 (Dll3) expression in the neural tube.
Delta-like 3 (Dll3) is a Delta family member expressed broadly in the developing nervous system as neural progenitor cells initiate differentiation. A proximal promoter sequence for Dll3 is conserved across multiple species and is sufficient to direct GFP expression in a Dll3-like pattern in the neural tube of transgenic mice. This promoter contains multiple E-boxes, the consensus binding site for bHLH factors. Dll3 expression and the activity of the Dll3-promoter in the dorsal neural tube depends on the basic helix-loop-helix (bHLH) transcription factors Ascl1 (Mash1) and Neurog2 (Ngn2). Mutations in each E-box identified in the Dll3-promoter allowed distinct enhancer or repressor properties to be assigned to each site individually or in combination. In addition, each E-box has distinct characteristics relative to binding of bHLH factors Ascl1, Neurog1, and Neurog2. Surprisingly, novel Ascl1 containing DNA binding complexes are identified that interact with specific E-box sites within the Dll3-promoter in vitro. These complexes include Ascl1/Ascl1 homodimers and Ascl1/Neurog2 heterodimers, complexes that in some cases require additional undefined factors for efficient DNA binding. Thus, a complex interplay of E-box binding proteins spatially and temporally regulate Dll3 levels during neural tube development.
Henke
R Michael
RM
Department of Neuroscience, UT Southwestern Medical Center, Dallas, TX 75390, USA.
Meredith
David M
DM
Borromeo
Mark D
MD
Savage
Trisha K
TK
Johnson
Jane E
JE
D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000502:physiology*; D001665:Binding Sites; D019281:Dimerization; D024721:E-Box Elements; D018507:Gene Expression Regulation, Developmental; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D054259:Neural Tube / Q000196:embryology / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D011401:Promoter Regions, Genetic; D013234:Stem Cells / Q000502:physiology
D051792:Basic Helix-Loop-Helix Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C499317:Ascl1 protein, mouse; C511877:Dll3 protein, mouse; C102938:Neurog2 protein, mouse