Adult flies carrying Syn2^NIG.4905R under the control of Scer\GAL4^GMR.PS exhibit abnormal eye morphology and are rough in appearance. When the copy number of Syn2^NIG.4905R is increased to two, the abnormality becomes more extensive, with many ommatidia lacking their regular hexagonal shape and bristles missing.

Adult flies carrying Syn2^NIG.4905R under the control of Scer\GAL4^pnr-MD237 exhibit cleft nota.

Eye imaginal discs expressing Syn2^NIG.4905R under the control of Scer\GAL4^GMR.PS show a significant increase in cell death signals posterior to the morphogenetic furrow in cells other than R-cells. The retinal depth of Scer\GAL4^GMR.PS>Syn2^NIG.4905R flies is significantly reduced compared to controls, indicating a requirement for Syn2 during the period of five-fold elongation of retinal cells. In contrast to the regular arrangement of ommatidial cells observed in wild-type flies, profound changes are noted in Scer\GAL4^GMR.PS>Syn2^NIG.4905R flies. Scer\GAL4^GMR.PS>Syn2^NIG.4905R flies raised at 25[o]C do not exhibit the rough-eye phenotype of those flies at 28[o]C. However, they significantly exhibit an increase in cell death and lack of retinal elongation compared to control flies. Rhabdomere trapezoidal organisation is disrupted, with the number of rhabdomere per ommatidium increasing up to 12. Rhabdomeres also show an abnormal morphology; they become enlarged and frequently split into two. Rhabdomeric microvilli exhibit a wild-type arrangement while F-actin accumulation at the apical surface is affected.

Adult flies carrying Syn2^NIG.4905R under the control of Scer\GAL4^Act5C.PU, Scer\GAL4^ey.PH, Scer\GAL4^rho.PL, Scer\GAL4^wg.PM, Scer\GAL4^e22c, Scer\GAL4^Bx-MS1096, Scer\GAL4^Dll-md23, Scer\GAL4^elav.PLu, Scer\GAL4^sd-SG29.1, Scer\GAL4^tey-5053A, Scer\GAL4^69B, Scer\GAL4^48Y, Scer\GAL4^Hml.PG or Scer\GAL4^Cg.PA exhibit no phenotypic defects.