title: Dose-dependent nuclear β-catenin response segregates endomesoderm along the sea star primary axis.
abstract: In many invertebrates, the nuclearization of β-catenin at one pole of the embryo initiates endomesoderm specification. An intriguing possibility is that a gradient of nuclear β-catenin (nβ-catenin), similar to that operating in vertebrate neural tube patterning, functions to distinguish cell fates in invertebrates. To test this hypothesis, we determined the function of nβ-catenin during the early development of the sea star, which undergoes a basal deuterostomal mode of embryogenesis. We show that low levels of nβ-catenin activity initiate bra, which is expressed in the future posterior endoderm-fated territory; intermediate levels are required for expression of foxa and gata4/5/6, which are later restricted to the endoderm; and activation of ets1 and erg in the mesoderm-fated territory requires the highest nβ-catenin activity. Transcription factors acting downstream of high nβ-catenin segregate the endoderm/mesoderm boundary, which is further reinforced by Delta/Notch signaling. Significantly, therefore, in sea stars, endomesoderm segregation arises through transcriptional responses to levels of nβ-catenin activity. Here, we describe the first empirical evidence of a dose-dependent response to a dynamic spatiotemporal nβ-catenin activity that patterns cell fates along the primary axis in an invertebrate.
authors.affiliation: Department of Biological Sciences, Carnegie Mellon University, 4400 5th Ave, Pittsburgh, PA 15213, USA.
authors.forename: Brenna S
authors.initials: BS
authors.lastname: McCauley
authors.affiliation: Department of Biological Sciences, Carnegie Mellon University, 4400 5th Ave, Pittsburgh, PA 15213, USA.
authors.forename: Eda
authors.initials: E
authors.lastname: Akyar
authors.affiliation: Department of Biological Sciences, Carnegie Mellon University, 4400 5th Ave, Pittsburgh, PA 15213, USA.
authors.forename: H Rosa
authors.initials: HR
authors.lastname: Saad
authors.affiliation: Department of Biological Sciences, Carnegie Mellon University, 4400 5th Ave, Pittsburgh, PA 15213, USA veronica@cmu.edu.
authors.forename: Veronica F
authors.initials: VF
authors.lastname: Hinman
mesh_terms: D000818:Animals; D036703:Blastula / Q000187:drug effects / Q000378:metabolism; D019521:Body Patterning / Q000187:drug effects / Q000235:genetics; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000378:metabolism; D004707:Endoderm / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks; D051543:Hepatocyte Nuclear Factor 3-gamma / Q000378:metabolism; D018021:Lithium Chloride / Q000494:pharmacology; D008648:Mesoderm / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism; D008954:Models, Biological; D051880:Receptors, Notch / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013215:Starfish / Q000196:embryology / Q000235:genetics; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D051880:Receptors, Notch; D051176:beta Catenin; D051543:Hepatocyte Nuclear Factor 3-gamma; D018021:Lithium Chloride
keywords: Echinoderm; Endomesoderm; Gene regulatory network; Nuclear β-catenin; Patiria