Fig. 4. R-cell specification in preclusters in hnt mutants. Eye discs containing clones of hnt tissue are shown. In all cases, the clone is marked by a lack of brown -HNT antibody staining. The location of the furrow together with the direction of the equator is indicated by the arrows. (A) Apical membrane expression of the R8 marker, Boss, visualized by -Boss antibody immunostaining in blue-black. Within the hnt patch, there is always a determined R8 cell, although occasionally there is a lower level of Boss accumulation than normal (red arrowheads). (B,C) Nuclear expression of the rho^PX81 enhancer trap, which labels determined R8, R2 and R5 precursor cells, visualized by -ß-gal antibody staining in blue-black and outlined in pink in the patch or in blue in surrounding wild-type clusters (C). Within the hnt patch, 47% of clusters have one or two non-staining cells, 74% of the clusters have misarrangements of their cells and 79% of the triads show misrotation of the cluster relative to its wild-type counterparts. (D,E) Nuclear expression of Spalt, which labels the R3 and R4 precursor cells, is shown by -Spalt antibody staining in blue-black. The nuclei of the R3 and R4 cells are outlined in blue in wild-type clusters or in yellow in cells in the hnt patch (E). Pale yellow indicates nuclei with reduced -Spalt staining. Inside the hnt patch, 57% of clusters have a non-staining cell, 84% have misarrangements of their cells and 67% show misrotation.