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GEO Series: GSE106320

Title: Bighead is a Wnt antagonist secreted by the Xenopus Spemann organizer that promotes Lrp6 endocytosis

Summary

The Xenopus laevis embryo has been subjected to almost saturating screens for molecules specifically expressed in dorsal Spemann organizer tissue. In this study, we performed high-throughput RNA sequencing of ectodermal explants, called animal caps, which normally give rise to epidermis. We analyzed dissociated animal cap cells that, through sustained activation of MAPK, differentiate into neural tissue. We also microinjected mRNAs for Cerberus, Chordin, FGF8, BMP4, Wnt8, and Xnr2, which induce neural or other germ layer differentiations. The searchable database provided here represents a valuable resource for the early vertebrate cell differentiation. These analyses resulted in the identification of a gene present in frog and fish, which we call Bighead. Surprisingly, at gastrula, it was expressed in the Spemann organizer and endoderm, rather than in ectoderm as we expected. Despite the plethora of genes already mined from Spemann organizer tissue, Bighead encodes a secreted protein that proved to be a potent inhibitor of Wnt signaling in a number of embryological and cultured cell signaling assays. Overexpression of Bighead resulted in large head structures very similar to those of the well-known Wnt antagonists Dkk1 and Frzb-1. Knockdown of Bighead with specific antisense morpholinos resulted in embryos with reduced head structures, due to increased Wnt signaling. Bighead protein bound specifically to the Wnt coreceptor lipoprotein receptor-related protein 6 (Lrp6), leading to its removal from the cell surface. Bighead joins two other Wnt antagonists, Dkk1 and Angptl4, which function as Lrp6 endocytosis regulators. These results suggest that endocytosis plays a crucial role in Wnt signaling.


Contributors: Edward De Robertis, Yi Ding, Gabriele Colozza, Eric Sosa, Yuki Moriyama, Samantha Rundle, Lukasz Salwinski

Experiment Type: A genome-wide study of the effects of vavious growth factors and dissociation on animal caps of Xenopus laevis

Experiment Reagents: bmp4, cer1, chrd.1,
fgf8, nodal2, tissue dissociation, wnt8a.


Phenotypes:
Xla Wt + animal cap explant + tissue dissociation + animal cap NF12 (RNA-Seq (RNA))

Article: XB-ART-55302, PubMed

Source: NCBI GEO, Xenbase FTP

Samples: (DEG = Differentially Expressed Genes; GSM = GEO Sample Number)
Sample View GSMs Assay Type
animal cap explant - NF12 GSM2835917  GSM2835921  GSM2835923  GSM2835927  RNA-Seq
Background: Xla.pigmentedNasco
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
explant   NF stage 9 animal cap
Conditions:
Tissue Assay Stages ChIP Antibody
animal cap NF stage 12  
   animal cap explant + bmp4 - NF12 DEG GSM2835919  RNA-Seq
Background: Xla.Outbred
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
mRNA injection bmp4 (Xla) bmp4 (Xla) NF stage 2 (2-cell) blastomere
explant   NF stage 9 animal cap
Conditions:
Tissue Assay Stages ChIP Antibody
animal cap NF stage 12  
   animal cap explant + cer1 - NF12 DEG GSM2835926  RNA-Seq
Background: Xla.Outbred
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
mRNA injection cer1 (Xla) cer1 (Xla) NF stage 2 (2-cell) blastomere
explant   NF stage 9 animal cap
Conditions:
Tissue Assay Stages ChIP Antibody
animal cap NF stage 12  
   animal cap explant + chrd.1 - NF12 DEG GSM2835920  RNA-Seq
Background: Xla.Outbred
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
mRNA injection chrd.1 (Xla) chrd.1 (Xla) NF stage 2 (2-cell) blastomere
explant   NF stage 9 animal cap
Conditions:
Tissue Assay Stages ChIP Antibody
animal cap NF stage 12  
   animal cap explant + nodal2 - NF12 DEG GSM2835929  RNA-Seq
Background: Xla.Outbred
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
mRNA injection nodal2 (Xla) nodal2 (Xla) NF stage 2 (2-cell) blastomere
explant   NF stage 9 animal cap
Conditions:
Tissue Assay Stages ChIP Antibody
animal cap NF stage 12  
   animal cap explant + tissue dissociation - NF12 DEG GSM2835918  GSM2835922  GSM2835924  RNA-Seq
Background: Xla.pigmentedNasco
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
explant   NF stage 9 animal cap
environmental treatment tissue dissociation NF stage 9 animal cap
Conditions:
Tissue Assay Stages ChIP Antibody
animal cap NF stage 12  
   animal cap explant + wnt8a + nodal2 - NF12 DEG GSM2835930  RNA-Seq
Background: Xla.Outbred
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
mRNA injection wnt8a (Xla) wnt8a (Xla) NF stage 2 (2-cell) blastomere
mRNA injection nodal2 (Xla) nodal2 (Xla) NF stage 2 (2-cell) blastomere
explant   NF stage 9 animal cap
Conditions:
Tissue Assay Stages ChIP Antibody
animal cap NF stage 12  
   animal cap explant + wnt8a - NF12 DEG GSM2835925  RNA-Seq
Background: Xla.Outbred
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
mRNA injection wnt8a (Xla) wnt8a (Xla) NF stage 2 (2-cell) blastomere
explant   NF stage 9 animal cap
Conditions:
Tissue Assay Stages ChIP Antibody
animal cap NF stage 12  
   animal cap explant+ fgf8 - NF12 DEG GSM2835928  RNA-Seq
Background: Xla.Outbred
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
mRNA injection fgf8 (Xla) fgf8 (Xla) NF stage 2 (2-cell) blastomere
explant   NF stage 9 animal cap
Conditions:
Tissue Assay Stages ChIP Antibody
animal cap NF stage 12  
dorsal embryo explant - NF12 GSM2835931  RNA-Seq
Background: Xla.pigmentedNasco
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
explant   NF stage 10 dorsal
Conditions:
Tissue Assay Stages ChIP Antibody
dorsal NF stage 12  
ventral embryo explant - NF12 GSM2835932  RNA-Seq
Background: Xla.pigmentedNasco
Manipulations:
Manipulation Type Reagent Target Gene Stage Treatment Area
explant   NF stage 10 ventral
Conditions:
Tissue Assay Stages ChIP Antibody
ventral NF stage 12  
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Xtr   
Xla 

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