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Fig. 2. Interommatidial cells in pupal eye imaginal discs overexpressing
crbintra or mutant for IrreC-rst are not properly
sorted and surplus cells fail to be eliminated. (A-C) Wild-type; (D)
GMR-Gal4>UAS-crbintra; (E) irreCCT.
Anti-DE-cadherin antibody was used to visualise the plasma membranes. (A) At
the onset of cell sorting (16% p.d.), formation of the primary pigment cells
(1°; blue) around the cone cell quartet (C) is complete. Sorting of the
interommatidial cells (IOC; brown) is in progress. Most ommatidial clusters
are still separated by more than one row of IOCs (arrowheads). (B) At 21%
p.d., cell sorting has been completed. The IOCs (brown) now form single rings
of lattice cells, aligned head-to-tail, separating the ommatidial clusters
from each other. b, bristle. (C) At 42% p.d. all surplus cells have been
eliminated by apoptosis. The remaining cells are now arranged in a regular
hexagonal pattern, in which secondary (2°) and tertiary (3°) pigment
cells, as well as bristles (b), can be distinguished. (D) Discs overexpressing
Crbintra, examined at 42% p.d., after the time at which cell death
occurs in the wild type. Cells are not properly rearranged and not all surplus
cells have been eliminated; occasionally two rows of cells are left between
ommatidial clusters (see also Fig.
5G,H). In several instances an `astral' arrangement of the 2°
and 3° pigment cells can be observed, in which four cells, instead of the
usual three, surround a bristle (arrowheads, compare with C). (E) An
irreC-rstCT retina at 40% p.d. Here, none of the surplus
cells has been eliminated, leaving the ommatidial clusters surrounded by two
or three rows of cells. The arrangement is similar of that seen in discs
overexpressing Crbintra, although the phenotype is stronger,
because the cell sorting is now disrupted in all instances (compare with
D).
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