Optical insulation of the unit eyes (ommatidia) is an important prerequisite of precise
sight with compound eyes. Separation of the ommatidia is ensured by pigment cells
that organize into a hexagonal lattice in the Drosophila eye, forming thin walls between
the facets. Cell adhesion, mediated by apically and latero-basally located junctional
complexes, is crucial for stable attachment of these cells to each other and the basal
lamina. Whereas former studies have focused on the formation and remodelling of the
cellular connections at the apical region, here, we report a specific alteration of
the lateral adhesion of the lattice cells, leaving the apical junctions largely unaffected.
We found that DAAM and FRL, two formin-type cytoskeleton regulatory proteins, play
redundant roles in lateral adhesion of the interommatidial cells and patterning of
the retinal floor. We show that formin-dependent cortical actin assembly is crucial
for latero-basal sealing of the ommatidial lattice. We expect that the investigation
of these previously unreported eye phenotypes will pave the way toward a better understanding
of the three-dimensional aspects of compound eye development.
