Differential regulation of eye specification in Drosophila by Polycomb Group epigenetic repressors.

During metazoan development, chromatin plasticity and genetic regulation are tightly connected to establish proper tissue fate and patterning. Drosophila imaginal discs are excellent models to study these processes as both genetic and mechanical injury can redirect their fate during regeneration. Reducing expression of Polycomb (Pc) results in the ectopic activation of the wing selector gene vestigial (vg) which in turn interacts with its DNA-binding partner Scalloped (Sd) - this forces the eye to transform into a wing. Reductions of other Polycomb Group members alone do not phenocopy this transformation. However, knocking down Sex comb on midleg (Scm) or Scm-related gene containing four mbt domains (Sfmbt) alongside the Pax6 gene twin of eyeless (toy) enables the eye-to-wing transformation. Using high throughput sequencing we show that toy-Sfmbt and toy-Scm knockdowns alter expression of both wing selector and Hox genes. These findings provide new insights into how the fate of the eye is specified.