While performing a reverse genetic screen with transposon insertion strains, we noticed that genotypes with increased resistance to ethanol sedation in eRING assays also often had strongly pigmented eyes from the mini-w eye color marker in the transposons. We therefore investigated the potential confound of mini-w expression in eRING studies by assessing ethanol sensitivity in three series of fly strains with graded levels of mini-w expression from transposon insertions (Figure S2). Expression of mini-w, which varies greatly in different transposon strains due to well-documented position effects (Hazelrigg et al., 1984; Silicheva et al., 2010), was ranked in our studies by eye color (w+-rank) by a single experimenter blind to genotype. The series of flies we assessed in eRING harbored (i) transposon insertions in three TGFβ receptor (TGFβR) genes (thickveins (tkv), wishful thinking (wit), and baboon (babo)), (ii) transposon insertions in the Akap200 locus, and (iii) several different Gal4 transgenes, all marked with mini-w in the same w1118 genetic background. Expression of mini-w from these transposon insertions strongly correlated with ethanol sensitivity in eRING assays (Figure 1A), but not with internal
