Biomedical Engineering Reference
In-Depth Information
literature with regard to the mechanism involved in N activation and how
this regulates cell fate (
del Alamo &Mlodzik, 2006; Fanto &Mlodzik, 1999;
Strutt et al., 2002; Weber, Paricio, &Mlodzik, 2000
). Recent data argue that
the Ral GTPase also plays a role in R3//R4 cell fate (
Cho & Fischer, 2011
).
2.4. Other manifestations of PCP
There are several other cell types/structures/tissues where
fz/stan
-based
PCP has been studied. Collier and colleagues discovered that the fly wing
has parallel cuticular ridges and that their orientation is under the control
of the
fz/stan
and
ds/ft
pathways (
Fig. 1.5E-G
)(
Valentine & Collier,
2011
). Interestingly, the ridges are oriented differently in the anterior and
posterior parts of the wing and this appears to be related to differences be-
tween two phases of
fz
signaling that utilize different
pk
isoforms (
Doyle,
Hogan, Lester, & Collier, 2008; Hogan, Valentine, Cox, Doyle, &
Collier, 2011; Valentine & Collier, 2011
). Their data also argue that the
early phase is dependent on
ds/ft
while the latter is not. The lateral side
branches of the arista are another body part where the
fz
pathway has
been found to regulate PCP (
He & Adler, 2002
). The laterals are
produced by polyploid cells and share features of both epidermal hairs and
bristles. As is the case for epidermal hairs, the
fz
pathway controls the
subcellular location for lateral outgrowth although in this cell type the
outgrowth is not juxtaposed to the distal most edge of the cell in wild
type (
He & Adler, 2002
).
The denticles that are part of the larval cuticle also display PCP, and they
have been intensively used as markers of pattern formation in embryonic seg-
ments. In recent years, they have also been used to study PCP (
Donoughe &
DiNardo, 2011; Price, Roberts, McCartney, Jezuit, & Peifer, 2006; Repiso,
Saavedra, Casal, & Lawrence, 2010
). Here, as in the adult abdomen, the
fz/
stan
and
ds/ft
systems appear to function in parallel.
The
fz/stan
pathway, which plays such a key role in PCP, has also been
found to regulate a number of processes that are not always thought of as
being related to PCP. The first of these to be identified was the formation
of the leg joints (
Held et al., 1986
). Mutations in genes such as
fz
give rise to
defective leg joints that often show mirror image symmetry typical of dupli-
cations (
Fig. 1.3E and F
). One often also sees “blebs.” The cellular basis for
this has not been established.
Mutations in genes such as
fz
also lead to occasional defects in wing evag-
ination so that the resulting wing points anteriorly in the pupal case (
Fig. 1.5A
and B
)(
Lee & Adler, 2002
). Such wings end up shorter and deformed,
