TY - JOUR
T1 - cis-Regulatory inputs of the wnt8 gene in the sea urchin endomesoderm network
AU - Minokawa, Takuya
AU - Wikramanayake, Athula H.
AU - Davidson, Eric H.
N1 - Funding Information:
This study was supported by the Lucille P. Markey Charitable Trust, and by NIH Grant HD37105 and DOE Grant DE-FG02-03ER63584. TM is very grateful to Chiou-Hwa Yuh, C. Titus Brown, and Roger Revilla-i-Domingo for their technical advice and useful discussions, and to Miki Yun for sequencing. TM received a travel grant (Sasakawa Grants for Science Fellows) from the Japan Science Society. Work in AHW's lab is supported by the National Science Foundation. AHW acknowledges the contributions of Jing Chen in the initial isolation of the Spwnt8 genomic clones.
PY - 2005/12/15
Y1 - 2005/12/15
N2 - Expression of the wnt8 gene is the key transcriptional motivator of an intercellular signaling loop which drives endomesoderm specification forward early in sea urchin embryogenesis. This gene was predicted by network perturbation analysis to be activated by inputs from the blimp1/krox gene, itself expressed zygotically in the endomesoderm during cleavage; and by a Tcf1/β-catenin input. The implication is that zygotic expression of wnt8 is stimulated in neighboring cells by its own gene product, since reception of the Wnt8 ligand causes β-catenin nuclearization. Here, the modular cis-regulatory system of the wnt8 gene of Strongylocentrotus purpuratus was characterized functionally, and shown to respond to blockade of both Blimp1/Krox and Tcf1/β-catenin inputs just as does the endogenous gene. The genomic target sites for these factors were demonstrated by mutation in one of the cis-regulatory modules. The Tcf1/β-catenin and Blimp1/Krox inputs are both necessary for normal endomesodermal expression mediated by this cis-regulatory module; thus, the genomic regulatory code underlying the predicted signaling loop thus resides in the wnt8 cis-regulatory sequence. In a second regulatory region, which initiates expression in micromere and macromere descendant cells early in cleavage, Tcf1 sites act to repress ectopic transcription in prospective ectoderm cells.
AB - Expression of the wnt8 gene is the key transcriptional motivator of an intercellular signaling loop which drives endomesoderm specification forward early in sea urchin embryogenesis. This gene was predicted by network perturbation analysis to be activated by inputs from the blimp1/krox gene, itself expressed zygotically in the endomesoderm during cleavage; and by a Tcf1/β-catenin input. The implication is that zygotic expression of wnt8 is stimulated in neighboring cells by its own gene product, since reception of the Wnt8 ligand causes β-catenin nuclearization. Here, the modular cis-regulatory system of the wnt8 gene of Strongylocentrotus purpuratus was characterized functionally, and shown to respond to blockade of both Blimp1/Krox and Tcf1/β-catenin inputs just as does the endogenous gene. The genomic target sites for these factors were demonstrated by mutation in one of the cis-regulatory modules. The Tcf1/β-catenin and Blimp1/Krox inputs are both necessary for normal endomesodermal expression mediated by this cis-regulatory module; thus, the genomic regulatory code underlying the predicted signaling loop thus resides in the wnt8 cis-regulatory sequence. In a second regulatory region, which initiates expression in micromere and macromere descendant cells early in cleavage, Tcf1 sites act to repress ectopic transcription in prospective ectoderm cells.
KW - Gene network
KW - Sea urchin embryo
KW - cis-regulation
KW - wnt8
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U2 - 10.1016/j.ydbio.2005.09.047
DO - 10.1016/j.ydbio.2005.09.047
M3 - Article
C2 - 16289024
AN - SCOPUS:29044443236
VL - 288
SP - 545
EP - 558
JO - Developmental Biology
JF - Developmental Biology
SN - 0012-1606
IS - 2
ER -