title: Establishment of mesodermal gene expression patterns in early Xenopus embryos: the role of repression.
abstract: In Xenopus, activin-like signals are able to induce and pattern mesoderm in a concentration-dependent manner. Previous experiments demonstrated that discrete gene expression patterns can be formed in animal cap explants as a response to graded activin signals. We analyzed the spatiotemporal appearance of goosecoid (gsc), chordin (chd), and Xbrachyury (Xbra) mRNAs in whole Xenopus embryos ectopically expressing activin or BVg1. To discriminate between direct transcriptional regulation and indirect, protein synthesis-dependent effects of ectopic signals, we combined overexpression studies and cycloheximide treatment. Our experiments revealed long-range signaling of activin/BVg1, but the expression patterns of gsc, chd, and Xbra in response to activin/BVg1 indicated that repressors are essential to establish the proper expression of these genes. Analysis of endogenous gsc, chd, and Xbra transcript distribution in embryos treated with cycloheximide supported this concept. We, therefore, conclude that inhibition is fundamental during early embryonic patterning.
authors.affiliation: Fakultät für Mathematik und Naturwissenschaften, Fachrichtung Biologie/Studiengang Molekulare Biotechnologie, Technische Universität Dresden, Dresden, Germany. thomas.kurth2@mailbox.tu-dresden.de <thomas.kurth2@mailbox.tu-dresden.de>
authors.forename: Thomas
authors.initials: T
authors.lastname: Kurth
authors.forename: Stefan
authors.initials: S
authors.lastname: Meissner
authors.forename: Simona
authors.initials: S
authors.lastname: Schäckel
authors.forename: Herbert
authors.initials: H
authors.lastname: Steinbeisser
mesh_terms: D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D004625:Embryo, Nonmammalian / Q000196:embryology* / Q000378:metabolism*; D005775:Gastrula / Q000187:drug effects / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000235:genetics*; D020868:Gene Silencing / Q000187:drug effects; D008648:Mesoderm / Q000187:drug effects / Q000378:metabolism*; D010641:Phenotype; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics* / Q000378:metabolism
chemical_list: D016212:Transforming Growth Factor beta; D029867:Xenopus Proteins; D003513:Cycloheximide