Genetic Modifiers of MeCP2 Figure 4. Novel genetic modifiers of the MeCP2 eye phenotype. A–B. MeCP2 expression by GMR-Gal4 at 30uC causes severe disorganization of the ommatidia and interommatidial bristles compared to controls. C–H. This phenotype is alleviated when combined with loss-of-function mutants in Asx, corto, osa, pbl, Scm, or overexpression of trc. I. In contrast, the loss-of-function trx allele enhances the external eye phenotype. J–L. When MeCP2 is driven by GMR-Gal4 at 27.5uC, the mild eye phenotype of MeCP2 is enhanced when combined with overexpression of Scm. M–R. Even though the MeCP2 flies do not show an eye phenotype at 25uC (N), when combined with either overexpression of osa (O) or pbl (Q), a strongly disrupted phenotype results that causes a loss of interommatidial bristles and, in the case of pbl, a reduction in the number of ommatidia. When osa and pbl are overexpressed alone, they have very mild phenotypes (P, R). Genotypes: A, GMR-Gal4/+. B, GMR-Gal4:UAS-MeCP2FLM119-2M/+. C, GMR- Gal4:UAS-MeCP2FLM119-2M/AsxXF23. D, GMR-Gal4:UAS-MeCP2FLM119-2M/+; cortoc03244/+. E, GMR-Gal4:UAS-MeCP2FLM119-2M/+; osa00090/+. F, GMR-Gal4: PLoS Genetics | www.plosgenetics.org 7 September 2008 | Volume 4 | Issue 9 | e1000179