title: Molecular patterning along the sea urchin animal-vegetal axis.
abstract: The molecular regulatory mechanisms underlying primary axis formation during sea urchin development have recently been identified. Two opposing maternally inherited systems, one animalizing and one vegetalizing, set up the animal-vegetal (A-V) axis. The vegetal system relies in part on the Wnt-beta-catenin-Tcf/Lef signaling pathway and the animal system is based on a cohort of animalizing transcription factors that includes members of the Ets and Sox classes. The two systems autonomously define three zones of cell-type specification along the A-V axis. The vegetalmost zone gives rise to the skeletogenic mesenchyme lineage; the animalmost zone gives rise to ectoderm; and the zone in which the two systems overlap generates endoderm, secondary mesenchyme, and ectoderm. Patterning along the A-V also depends on cellular interactions involving Wnt, Notch, and BMP signaling. We discuss how these systems impact the formation of the second axis, the oral-aboral axis; how they connect to later developmental events; and how they lead to cell-type-specific gene expression via cis-regulatory networks associated with transcriptional control regions. We also discuss how these systems may confer on the embryo its spectacular regulatory capacity to replace missing parts.
authors.affiliation: Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Bruce P
authors.initials: BP
authors.lastname: Brandhorst
authors.forename: William H
authors.initials: WH
authors.lastname: Klein
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000502:physiology*; D002454:Cell Differentiation / Q000235:genetics*; D019070:Cell Lineage / Q000235:genetics*; D016764:Cell Polarity / Q000235:genetics; D004627:Embryonic Induction / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D005855:Germ Layers / Q000166:cytology / Q000378:metabolism*; D012617:Sea Urchins / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics
chemical_list: D014157:Transcription Factors