Polychaetoid is required to restrict segregation of sensory organ precursors from proneural clusters in Drosophila.

Reduction of wild-type activity of the polychaetoid (pyd) gene results in formation of extra mechanosensory bristles on the head and notum of adult Drosophila. Loss of pyd function results in decreased ability to restrict sensory organ precursor (SOP) formation to a single cell per proneural cluster. Although the initial proneural cluster pattern of achaete expression is not altered in pyd mutants, extra cells within proneural clusters express the high levels of achaete characteristic of SOPs. This observation suggests that pyd+ functions as a negative regulator of achaete-scute complex expression within the proneural cluster. Synergistic interactions between pyd and Notch, Delta and extramacrochaetae mutations support this model. We also demonstrate that pyd is required for normal eye development.