Biomedical Engineering Reference
In-Depth Information
A
B
T cell
LIN-44
P2
MOM-2
MES-1
EMS
Hypodermal
Neural
Endoderm
MES-1
-
MES-1
+
LIN-44
MOM-2
+
MOM-2
-
EMS
Neural
Hypodermal
Endoderm
Figure 3.3 Wnts function as polarity cues. (A) The EMS polarity is controlled by the MES-1
and MOM-2/Wnt signals from the P2 cell. When isolated wild-type EMS is combined with
two P2 cell mutants of mes-1 or mom-2, endoderm produced from an EMS daughter pro-
duced on the sidewithmes-1 P2was attached. (B) The T-cell polarity is controlled by LIN-44
fromits posterior neighbor cell.WhenLIN-44 is expressedon theanterior sideof the T cell in
lin-44 mutants, the T-cell polarity is nearly completely reversed.
production from the EMS daughter contacting with
mom-2-
positive P2
lacking
mes-1
, showing that
mom-2
rather than
mes-1
functions as a polarity
cue. Postembryonic T-cell polarity is controlled by
lin-44
/Wnt that is
expressed in hypodermal cells just posterior to the T cell (
Fig. 3.3
B). Ectopic
expression of
lin-44
anterior to the T cell in the absence of endogenous
lin-44
function causes strong reversal of the T-cell polarity. These observa-
tions show that Wnt signals determine the orientation of cell polarity at least
when Wnts are produced close to the polarizing cells.
6. COORDINATION OF SPINDLE ORIENTATION BY
MOM-2/Wnt
In terms of global cell polarization, at least spindle orientation in
embryonic cells was shown to be coordinated by the Wnt signal from the
P2 blastomere or its descendants that positions at the posterior end of embryos
(
Bischoff & Schnabel, 2006
). The progeny of isolated AB cell daughters
