Biomedical Engineering Reference
In-Depth Information
A
AB.a
AB.a
B
AB.p
P2
AB.p
C
AB.p
P2
AB.p
D
AB.p
AB.p
AB.p
AB.p
P2
P2
AB.p
AB.p
AB.p
AB.p
E
AB.p
AB.p
AB.p
AB.p
P2
P2
AB.p
AB.p
AB.p
AB.p
Figure 3.4 Coordination of spindle orientation by MOM-2/Wnt. (A) Isolated AB blasto-
mere cultured alone produce embryonic fragments without elongation and with ran-
dom spindle orientation (without the glp-1 signal from P2, AB daughters adopt the
AB.a fate). Embryonic fragments elongated with biased spindle orientation toward
P2 when AB is combined with wild-type P2 (B) but not with mom-2 P2 (C). The elonga-
tion occurs when two ABs were combined followed by laser ablation of the central AB
daughters (D) but not when central AB is from a mom-2 embryo (E).
without P2 cell divides in randomorientation (
Fig. 3.4
A). However, combin-
ing the P2 blastomere with AB causes division orientations of AB descendants
as well as those of P2 to be biased toward P2, resulting in elongation of the
embryonic fragment (
Fig. 3.4
B). This signaling requires MOM-2/Wnt in
P2 and MOM-5/Frizzled in AB daughters (
Fig. 3.4
C). When P2 is combined
with two pairs of AB daughters followed by laser ablation of an AB daughter
