Biomedical Engineering Reference
In-Depth Information
Figure 1.1 Hair polarity on the fly wing. A shows the polarity of hairs on the dorsal sur-
face of a wild-type wing. B shows the stereotypic pattern seen on the dorsal surface of
an inturned wing. The blackened area is where the polarity was too variable to draw a
consensus vector. C shows images of wings from two regions (noted in A) of Oregon R,
fz, in, and mwh mutant wings. Note the relative similarity of the polarity patterns. The
downstream genes often show a slightly stronger polarity disruption, but with similar
directionality. D shows an fz clone marked by the cell marker strb (causes short de-
formed and multiplied hairs). E a pk clone marked by sha (causes a loss of hairs) and
FaVang clone marked by sha. Arrows show local hair polarity.
give rise to the cells of the sense organ (
Gho & Schweisguth, 1998; Lu, Usui,
Uemura, Jan, & Jan, 1999
)(
Fig. 1.3B
). On the leg, some bristle sense organs
signal to a neighboring epidermal cell to form a bract (
Fig. 1.3C
). This
involves the EGFR pathway, and this system displays planar polarity as
the bract is routinely proximal to the bristle (
Held, 2002
)(
Fig. 1.3
). Most
leg bristles do not show strongly abnormal polarity in
fz/stan
pathway
mutants but
in those that do the bract
is coordinately positioned
“upsteam” (
Fig. 1.3D
).
2.3. The eye
The third developmental unit that has been extensively studied with respect
to PCP is the ommatidia of the compound eye (
Zheng, Zhang, & Carthew,
1995
). Each ommatidia is comprised of about 20 cells
including
