Multiple Wnt Signaling Pathways Converge to Or ient the Mitotic Spindle in Early C. elegans Embryos Walston T. et al. Developmental Cell, Vol. 7, 831–841, December, 200
Dec 16, 2015
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
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
Background
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...
dsh-2(or302)
dsh-1(RNAi); dsh-2(or302); mig-5(RNAi)
Defects in Alignment of the EMS and ABar Spindles.
Defects in EMS
KIN-19/CKⅠ localizes to centrosomes and DSH-2 accumulates between P2 and EMS.
microtubule condensed chromosome
~4cell stage 4~6cell stage 6~32cell stage
cytoplasm 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.
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.
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
ABar spindle defects visualized by -tubulin::GFP
dsh-2(RNAi); mig-5(RNAi) wrm-1(RNAi)
TBB-2/ -tubulin::GFP
Three Wnt signaling pathways operate in the Early C. elegans embryos.
G signaling in spindle orientation ??
GSK-3 in spindle orientation ??
Discussion
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
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.
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
Activation of G signaling downstream of Wnt-11/Xfz7 regulates Cdc42 activity.
Penzo-Mendez A et al. Dev Biol, 2003.
During xenopus gastrulation
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
Axin
APC
-cat
-cat-cat
CKⅠ
-cat
-catTcf/Lef
Dvl
RhoA
MEKK, SEK
JNK
PKC
Cdc42
Par-6PKC
Polarity
Cell fate,spindle rotation
Mes-1