Drosophila homeodomain protein dHb9 directs neuronal fate via crossrepressive and cell-nonautonomous mechanisms.
Here we present the identification and characterization of dHb9, the Drosophila homolog of vertebrate Hb9, which encodes a factor central to motorneuron (MN) development. We show that dHb9 regulates neuronal fate by restricting expression of Lim3 and Even-skipped (Eve), two homeodomain (HD) proteins required for development of distinct neuronal classes. Also, dHb9 and Lim3 are activated independently of each other in a virtually identical population of ventrally and laterally projecting MNs. Surprisingly, dHb9 represses Lim3 cell nonautonomously in a subset of dorsally projecting MNs, revealing a novel role for intercellular signaling in the establishment of neuronal fate in Drosophila. Lastly, we provide evidence that dHb9 and Eve regulate each other's expression through Groucho-dependent crossrepression. This mutually antagonistic relationship bears similarity to the crossrepressive relationships between pairs of HD proteins that pattern the vertebrate neural tube.
Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, USA.
Heather T
HT
Broihier
James B
JB
Skeath
D000818:Animals; D001426:Bacterial Proteins; D051792:Basic Helix-Loop-Helix Proteins; D002450:Cell Communication / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D019070:Cell Lineage / Q000235:genetics*; D002633:Chemotaxis / Q000235:genetics; D002828:Choristoma / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology* / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D020439:Growth Cones / Q000378:metabolism / Q000648:ultrastructure; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009420:Nervous System / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C052837:eve protein, Drosophila; C490005:exex protein, Drosophila; C091023:gro protein, Drosophila