Intrinsic differences between the superficial and deep layers of the Xenopus ectoderm control primary neuronal differentiation.
In Xenopus, primary neurons differentiate early, in the deep layer of the neuroectoderm. In contrast, the neural precursors of the superficial layer continue to proliferate. We report that superficial layer precursors differ from deep layer precursors in that they are refractory to the neuronal-promoting activity of bHLH genes, dominant-negative X-Delta-1, FGF-8, or signals from the organizer. In this system, neuronal differentiation is guided by an early established, intrinsic, cell-autonomous difference in the competence of the precursor cells to differentiate. This difference may be controlled in part by ESR6e, a bHLH gene of the Enhancer-of-split family, which is expressed in the superficial layer of the late blastula and when expressed ectopically suppresses primary neurogenesis in the deep layer.
Chalmers
Andrew D
AD
Wellcome/CRC Institute, Tennis Court Road, CB2 1QR, Cambridge, United Kingdom.
Welchman
David
D
Papalopulu
Nancy
N
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins; D015415:Biomarkers / Q000032:analysis; D001755:Blastocyst / Q000166:cytology / Q000378:metabolism; D019070:Cell Lineage; D016764:Cell Polarity; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004475:Ectoderm / Q000166:cytology* / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D004627:Embryonic Induction; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000378:metabolism; D005775:Gastrula / Q000166:cytology / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D009024:Morphogenesis; D009420:Nervous System / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014981:Xenopus / Q000196:embryology* / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D015415:Biomarkers; D004268:DNA-Binding Proteins; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; C064045:delta protein