Consequently, we cannot exclude the possibility that the site of transgene insertion rather than the RNAi effect itself caused the observed modification on the polyQ-induced REP. In our screen, the plethora of individual RNAi lines and the high number of candidates prevented us to test for potential off-target and/or genetic background effects. Apart of these drawbacks, using RNAi libraries has certain R428 advantages to screen for modifiers of polyQinduced induced toxicity. For example, previous screens on modifiers of polyQ-induced REPs utilized P-element gene disruption or EP-element-driven overexpression/silencing of genes. Although these screens provided valuable insights in the mechanisms of polyQ-induced toxicity, a drawback of P/EPelement-based screens is the limited amount of available elements and the unknown/low number of targeted genes. In agreement with previous reports, our analysis on polyQ aggregation of selected candidates revealed a dissociation of toxicity and aggregation. We found that only a minor portion of analyzed suppressors had a significant effect on polyQ aggregation. More precisely, suppressors caused either a reduction or an increase of aggregated polyQ species compared to control, as visualized by filter retardation assay. We are aware that the filter retardation assay might not perfectly reflect actual aggregate load. According to the pore size of the membrane, we might not be able to detect aggregates with a diameter smaller than the pore. In addition, we might pellet extremely high molecular weight aggregates by centrifugation steps in sample preparation and thus deplete these aggregate species from our analysis. In case of the analyzed enhancers, there was no clear trend towards increased aggregation. In contrast, almost all analyzed enhancers displayed a slightly reduced aggregate load. However, the high degree of retina cell loss observed for enhancers might bias the actual aggregate load due to a reduction in the absolute number of polyQ-expressing cells present at the time of analysis. In summary, our findings nevertheless imply absence of correlation between toxicity and aggregation. This was at least partially unexpected as previous analyses implicated such a correlation and convincingly proved this assumption with a wide range of experimental approaches. A smaller sample number in previous reports might account for the discrepancy compared to our analysis. The computational analysis of our candidate gene set highlights the broad range of molecular functions that might affect polyQmediated toxicity. The network-based approach utilizes subtle phenotypic changes of some candidates to tie links between strong candidate genes. While not all subtle candidates may be ‘true’, a good proportion actually does make sense in the light of the network- and Gene Ontology analysis. A future challenge will be the identification and assessment of the most important functional categories that might moderate polyQ-induced toxicity. Previously, we utilized the zebrafish model to separate the maternal and embryonic requirement vitamin E deficiency. We reported that a-tocopherol-deficient fish spawn and produce viable eggs, but within days the embryos and larvae display developmental impairment and increased risk of mortality, establishing a critical embryonic need for a-tocopherol. Zebrafish nutrients are derived solely from the yolk sac for the initial 4–5 days post fertilization.