Sensitivity of proneural genes to lateral inhibition affects the pattern of primary neurons in Xenopus embryos.
We have compared the roles of XASH-3 and NeuroD, two basic helix-loop-helix transcription factors, in the formation of primary neurons in early Xenopus embryos. When ectopically expressed in Xenopus embryos, XASH-3 and NeuroD induce ectopic primary neurons in very different spatial patterns. We show that the pattern of primary neurons induced by XASH-3 and NeuroD can be accounted for by a difference in their sensitivity to inhibitory interactions mediated by the neurogenic genes, X-Delta-1 and X-Notch-1. Both NeuroD and XASH-3 promote the expression of the inhibitory ligand, X-Delta-1. However, XASH-3 appears to be sensitive to the inhibitory effects of X-Delta-1 while NeuroD is much less so. Consequently only a subset of cells that ectopically express XASH-3 eventually form neurons, giving a scattered pattern, while the ectopic expression of NeuroD leads to a relatively dense pattern of ectopic neurons. We propose that differences in the sensitivity of XASH-3 and NeuroD to lateral inhibition play an important role during their respective roles in neuronal determination and differentiation.
Chitnis
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The Salk Institute for Biological Studies, San Diego, CA 92186-5800, USA.
Kintner
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C
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D002454:Cell Differentiation / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D005809:Genes, Regulator / Q000502:physiology; D018257:Helix-Loop-Helix Motifs / Q000235:genetics*; D017403:In Situ Hybridization; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009420:Nervous System / Q000166:cytology / Q000196:embryology*; D009474:Neurons / Q000502:physiology; D012313:RNA / Q000235:genetics / Q000494:pharmacology; D013234:Stem Cells; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014981:Xenopus / Q000196:embryology* / Q000235:genetics
D051792:Basic Helix-Loop-Helix Proteins; D009419:Nerve Tissue Proteins; D012313:RNA; D014157:Transcription Factors; C093564:Neurogenic differentiation factor 1