Alteration of wing size through over-expression of scribbler isoforms.

Scribbler was identified as a genetic modifier of the Drosophila tumor suppressor gene Merlin. Loss of Merlin results in hyperplasia in a number of different epithelial tissues including the wing and eye imaginal discs, however loss of scribbler does not. The lack of an overt proliferation sbb phenotype has complicated the mechanistic link between sbb and Merlin. Scribbler encodes two novel transcriptional repressors which function in numerous processes including axon guidance and pattern formation within the wing. While the two sbb isoforms have some redundant functions over-expression of two sbb isoforms within the wing show distinct and opposite effects. Over-expression of the smaller SbbA isoform results in a larger wing, while over-expression of larger SbbB isoform results in a smaller wing with defects in venation. Co-expression of sbb isoforms ameliorates the effects of expression of either isoform alone, suggesting that a balance between the express of each scribbler isoform is required to ensure proper size of the wing.