Refinement of gene expression patterns in the early Xenopus embryo.
During blastula and gastrula stages of Xenopus development, cells become progressively and asynchronously committed to a particular germ layer. We have analysed the expression of genes normally expressed in ectoderm, mesoderm or endoderm in individual cells from early and late gastrula embryos, by both in situ hybridization and single-cell RT-PCR. We show that at early gastrula stages, individual cells in the same region may express markers of two or more germ layers, and 'rogue' cells that express a marker outside its canonical domain are also observed at these stages. However, by the late gastrula stage, individual cells express markers that are more characteristic of their position in the embryo, and 'rogue' cells are seen less frequently. These observations exemplify at the gene expression level the observation that cells of the early gastrula are less committed to one germ layer than are cells of the late gastrula embryo. Ectodermal cells induced to form mesendoderm by the addition of Activin respond by activating expression of different mesodermal and endodermal markers in the same cell, recapitulating the response of marginal zone cells in the embryo.
Wardle
Fiona C
FC
Wellcome Trust/Cancer Research UK Gurdon Institute and Department of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QR, UK. f.wardle@gurdon.cam.ac.uk
Smith
James C
JC
D028341:Activins / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects; D004247:DNA / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D004627:Embryonic Induction / Q000187:drug effects; D005775:Gastrula / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D051956:Goosecoid Protein; D006609:High Mobility Group Proteins / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics; D017403:In Situ Hybridization; D011518:Proto-Oncogene Proteins / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D055760:SOXF Transcription Factors; D014157:Transcription Factors / Q000235:genetics; D051153:Wnt Proteins; D029867:Xenopus Proteins / Q000235:genetics; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics*
D004268:DNA-Binding Proteins; D051956:Goosecoid Protein; D006609:High Mobility Group Proteins; D018398:Homeodomain Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D055760:SOXF Transcription Factors; D014157:Transcription Factors; D051153:Wnt Proteins; D029867:Xenopus Proteins; C491602:sox17a protein, Xenopus; D028341:Activins; D004247:DNA