Loss of <i>fatp</i> induces adult-onset progressive degeneration of PRs.

<p>(A–G) Consequences of <i>fatp</i> knockdown by RNA interference on PR viability. (A, B, C) Visualization of PRs using a cornea-neutralization method for 1-, 15- and 21-day-old PRs expressing <i>lacZ</i> as a control. (D, E, F) PRs expressing the <i>fatp</i>-interfering RNA and (G) PR quantification. Whereas all PRs were present in control retina and <i>fatp</i>-knocked-down retina at day one (A, D), there were significant PR losses at days 15 and 21 in <i>fatp</i>-knocked-down retina (B vs E, C vs F, t-test, n≥6). (H) Time-course analysis of <i>fatp^k10307</i> mutant mosaic retina using the Tomato/GFP-FLP/FRT method and (I) quantification. All outer PRs (R1–R6) expressed GFP (green). FLP-mediated mitotic mutant clones were visualized by the absence of rh1-tdTomato (red). Clones of the same eye were visualized in the same fly at day one, four, eight and fourteen after hatching. (H) All PRs were present at day one (scale bar = 10 µm). (H′) From day four, mutant PRs (in green) started to disappear. (H″ and H′″) Losses of mutant PRs were significant at day eight and day fourteen (paired t-test, n = 3). (I) Quantified results are expressed as mean ± SD. (J) Analysis of a control 15-day-old mosaic retina using the Tomato/GFP-FLP/FRT method. All PRs are present. (K–N) Rescue of <i>fatp^k10307</i>-mutant PRs by re-expression of wild-type <i>fatp</i>. (K) Tomato/GFP-FLP/FRT visualization of 10- to 14-day-old control, (L) <i>fatp^{k10307/k10307}</i> and (M) <i>fatp^{k10307/k10307}+rh1>fatp</i> mosaic retinas and (N) quantification (t-test, n> = 5). In the control (K), all PRs were present. In <i>fatp</i> mutant mosaic retina (L), 70% of the mutant PRs were lost. In these retinas, mutant PRs were rescued by re-expression of <i>fatp</i> under the control of the <i>rh1</i> promoter (M).