|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
|
Fig. 2. Developmental profile of scaffold axon outgrowth, glial migration and
retinal innervation. Wg expression commences in the mid-1st instar larval
stage in a pair of domains in the outer anlagen, preceding retinal innervation
by several days. Scaffold axon fascicle elaboration was visualized by
wg-lacZ expression (blue in A-E or white in A'-E'). Glia
were visualized by anti-Repo staining (red in all panels). Neuronal cell
bodies and neuropiles were visualized by anti-HRP staining (green in A-E).
Above each optic lobe image, which shows a different time point (youngest at
left in A), is a schematic diagram indicating the state of ommatidial
development in terms of the number of ommatidial columns. The developing optic
lobe is outlined in white in A-E and yellow in A'-E'. (A,A')
An early 2nd instar stage specimen, lacking any retinal innervation (0
columns), in which the two Wg domains contain a small number of cells. A small
island of Repo-positive glia are observed in the prospective photoreceptor
axon target region (arrowhead). Scaffold axon fascicles are not detected.
(B,B') A mid-2nd instar specimen, a time point just prior to ommatidial
development. The anlage have grown in size, but scaffold axon tracts are not
yet detectable. (C,C') A late 2nd instar specimen in which one
ommatidial column is detected in the retina, and a small amount of retinal
innervation has occurred. The medulla neuropile has just begun formation.
Scaffold axon fascicles are clearly visible emanating from the Wg domains and
extending towards the neuropile (green arrowheads in C'). There is an
increase in glia number within the neuropile region at this time point (yellow
arrowhead). (D,D') An early 3rd instar stage animal in which three
columns of developing ommatidia were present in the retina. Scaffold axon
fascicles begin to elaborate an architecture reminiscent of the late third
instar (compare with Fig. 1C),
in which tracts for medulla neuropile glia and lobula neuropile glia are
distinguishable (green arrowheads in D'). Considerably more glia are
visible in the neuropile region (yellow arrowhead in D') in the focal
plane shown. (E,E') A mid-3rd instar stage specimen in which seven
columns of ommatidia were detected in the retina. Scaffold axon fascicles for
MNG glial migration are indicated (green arrowheads in E').
|
