title: Morphogen rules: design principles of gradient-mediated embryo patterning.
abstract: The Drosophila blastoderm and the vertebrate neural tube are archetypal examples of morphogen-patterned tissues that create precise spatial patterns of different cell types. In both tissues, pattern formation is dependent on molecular gradients that emanate from opposite poles. Despite distinct evolutionary origins and differences in time scales, cell biology and molecular players, both tissues exhibit striking similarities in the regulatory systems that establish gene expression patterns that foreshadow the arrangement of cell types. First, signaling gradients establish initial conditions that polarize the tissue, but there is no strict correspondence between specific morphogen thresholds and boundary positions. Second, gradients initiate transcriptional networks that integrate broadly distributed activators and localized repressors to generate patterns of gene expression. Third, the correct positioning of boundaries depends on the temporal and spatial dynamics of the transcriptional networks. These similarities reveal design principles that are likely to be broadly applicable to morphogen-patterned tissues.
authors.affiliation: The Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK james.briscoe@crick.ac.uk sjs1@nyu.edu.
authors.forename: James
authors.initials: J
authors.lastname: Briscoe
authors.affiliation: Department of Biology, New York University, 100 Washington Square East, New York, NY 10003, USA james.briscoe@crick.ac.uk sjs1@nyu.edu.
authors.forename: Stephen
authors.initials: S
authors.lastname: Small
mesh_terms: D000818:Animals; D001756:Blastoderm / Q000502:physiology; D019521:Body Patterning; D004331:Drosophila melanogaster / Q000196:embryology*; D004625:Embryo, Nonmammalian / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks; D008962:Models, Theoretical; D054259:Neural Tube / Q000196:embryology; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D014157:Transcription Factors
keywords: Bicoid; Drosophila blastoderm; Gene regulatory network; Morphogen interpretation; Sonic hedgehog; Vertebrate neural tube