The Xenopus homolog of Drosophila Suppressor of Hairless mediates Notch signaling during primary neurogenesis.
The X-Notch-1 receptor, and its putative ligand, X-Delta-1, are thought to mediate an inhibitory cell-cell interaction, called lateral inhibition, that limits the number of primary neurons that form in Xenopus embryos. The expression of Xenopus ESR-1, a gene related to Drosophila Enhancer of split, appears to be induced by Notch signaling during this process. To determine how the activation of X-Notch-1 induces ESR-1 expression and regulates primary neurogenesis, we isolated the Xenopus homolog of Suppressor of Hairless (X-Su(H)), a component of the Notch signaling pathway in Drosophila. Using animal cap assays, we show that X-Su(H) induces ESR-1 expression, perhaps directly, when modified by the addition of ankyrin repeats. Using a DNA binding mutant of X-Su(H), we show that X-Su(H) activity is required for induction of ESR-1. Finally, expression of the DNA binding mutant in embryos leads to a neurogenic phenotype as well as increased expression of both X-Delta-1 and XNGNR1, a proneural gene expressed during primary neurogenesis. These results suggest that activation of X-Su(H) is a key step in the Notch signaling pathway during primary neurogenesis in Xenopus embryos.
Wettstein
D A
DA
Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037-1099, USA.
Turner
D L
DL
Kintner
C
C
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004330:Drosophila / Q000196:embryology* / Q000235:genetics; D029721:Drosophila Proteins; D007301:Insect Hormones / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009420:Nervous System / Q000196:embryology*; D011485:Protein Binding; D051880:Receptors, Notch; D012091:Repetitive Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics*; D014981:Xenopus / Q000196:embryology* / Q000235:genetics
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D007301:Insect Hormones; D008565:Membrane Proteins; D051880:Receptors, Notch; D012097:Repressor Proteins; C084530:E(spl)mdelta-HLH protein, Drosophila; C497759:N protein, Drosophila; C088731:Su(H) protein, Drosophila