Mutation of twins encoding a regulator of protein phosphatase 2A leads to pattern duplication in Drosophila imaginal discs.

The Drosophila gene twins was identified through a P-element-induced mutation that caused overgrowth in posterior regions of the wing imaginal disc. Analyses using position-specific markers showed that the inactivation of this locus induced the formation of extra wing blade anlagen in the posterior compartment of the disc. The duplication was mirror symmetrical, and the line of the symmetry did not correspond to any of the known compartment borders. We isolated the twins gene and found that it encoded one of the regulatory subunits of protein phosphatase 2A (PP2A). These results suggest a novel aspect of physiological roles of protein dephosphorylation; that is, the control of PP2A activity is crucial for specification of tissue patterns.