Multiple Wnt Signaling Pathways Converge to Orient
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Transcript of Multiple Wnt Signaling Pathways Converge to Orient
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Multiple Wnt Signaling Pathways Converge to Orient
the Mitotic Spindle in Early C. elegans Embryos
Walston T. et al.Developmental Cell, Vol. 7, 831–841, December, 2004
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ABpl
The fate of the EMS daughters is controlledby a Wnt/b-cat pathway.
The orientation of the EMS division is controlled by a different Wnt pathway involving Wnt(MOM-2), Porcupine(Porc;MOM-1), Fz(MOM-5), GSK-3(GSK-3b) and CK1(KIN-19).
A pathway involving MES-1, a receptor tyrosine kinase, and SRC-1, a Src family tyrosine kinase, acts redundantly with Wnt signaling with respect to the fate of EMS daughters and the orientation of the EMS spindle.
mom-1 (Porc), mom-2 (Wnt), mom-5 (Fz), and mom-3 (uncloned), cause spindle alignment defects in the ABar blastomere of the 8-cell embryo.
Background
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Background
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Although many Wnt signaling components have been identified that participate in spin
dle orientation, the role of the Dsh family has not been clearly characterized.
(dsh-1, dsh-2, mig-5)
Loss of function of the CKI homolog, kin-19, causes defects in the fate of EMS daughter
cells. Although the role of CKI in spindle alignment has not been examined, CKI localizes t
o centrosomes and mitotic spindles in vertebrate systems.
The nontranscriptional Wnt spindle alignment pathway requires contact from the C blas
tomere to align the spindle of ABar.
Wnt/b-catenin pathway regulates the timing of spindle rotation in ABar, presumably by
specifying the fate of neighboring blastomeres.
We demonstarate...
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dsh-2(or302)
dsh-1(RNAi); dsh-2(or302); mig-5(RNAi)
Defects in Alignment of the EMS and ABar Spindles.
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Defects in EMS
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KIN-19/CKⅠ localizes to centrosomes and DSH-2 accumulates between P2 and EMS.
microtubule condensed chromosome
~4cell stage 4~6cell stage 6~32cell stagecytoplasm boundary
between P2 and EMS
cortex of all cells
Consistent with P2 signaling to EMS to specify endoderm fate and EMS spindle orientation.
KIN-19 RNAi → does not affect Dsh-2 localization.
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Fz
APCAxin
b-catNEMO
TCFRNA pol.
Positive : Dsh, CK , GSK-3, Src (Dsh background)ⅠNegative : JNK, APC, Axin, b-cat, NEMO, TCF, RNA pol.
Spindle defects in ABar.
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Contact with the C blastomere aligns the spindle in ABar.
Caudalhomolog
laserkilled
Mom-2(Wnt)
Mom-5(Fz) Mom-5(Fz)
canonical non-canonical
C
EMS ABar
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ABar spindle defects visualized by -tubulin::GFP
dsh-2(RNAi); mig-5(RNAi) wrm-1(RNAi)
TBB-2/ -tubulin::GFP
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Three Wnt signaling pathways operate in the Early C. elegans embryos.
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G signaling in spindle orientation ??
GSK-3 in spindle orientation ??
Discussion
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Heterotrimeric G-protein in spindle orientation
G : GPB-1, GPB-2G : GPC-1, GPC-2
Gotta M et al, Nat Cell Biol, 2001.
A P
D
V
ABaABp
P2
EMS
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Heterotrimeric G-protein in spindle orientation
C. elegans has 20G genes. → GOA-1, GPA-16
Conclusion : G signaling, not G, participates spindle orientation in C. elegans.
Gotta M et al, Nat Cell Biol, 2001.
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Cdc42 regulates GSK-3 and APC to control cell polarity.
There is a larger complex containing GSK-3, Par6, PKC.
Scratch-induced cell migration assay : Cdc42, p-GSK-3-cat and APC localize at the leading edge of migrating cell.
Etienne-Manneville S et al. Nature, 2003.
Astrocyte
MTOC : microtubule organizing centre
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Activation of G signaling downstream of Wnt-11/Xfz7 regulates Cdc42 activity.
Penzo-Mendez A et al. Dev Biol, 2003.
During xenopus gastrulation
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Cdc42, p-GSK-3-cat, APC
Leading edge
Dvl-1 ?Dvl-2 ?Dvl-3 ?
Src
Canonical Wnt
Fz
Non-canonical Wnt
FzG
Dvl
GSK-3
AxinAPC
-cat
-cat-cat
CKⅠ
-cat
-catTcf/Lef
Dvl
RhoA
MEKK, SEK
JNK
PKC
Cdc42
Par-6PKC
Polarity
Cell fate,spindle rotation
Mes-1