Overexpression of oc^hs.PR for 20 minutes at stage 7-8 leads to a dramatic transformation of the nervous system; suppression of the ventral nerve cord is often seen. Severe disruption of the peripheral nervous system in the trunk region is also seen, suggesting general segmentation defects in the posterior part of the embryo. The anterior nervous structures are often present or enhanced in many cases.

Ectopic expression of oc^hs.PR using a 45 minute heat shock between 2.5 and 5.5 hours after egg laying causes severe disruption of the head skeleton, with a mass of scleral tissue frequently forming in place of a defined head skeleton. The major plate of the maxillary sense organ is often reduced in size and has fewer papillae than in control heat-shocked embryos, and the number of cirri are reduced. The antennal sense organ is sometimes duplicated, the dorsolateral papilla is generally not lost, and ectopic dorsomedial papillae are often seen.

Overexpression of oc^hs.PR in a wild-type background at stage 7-8 by a continuous heat shock of over 20 minutes at 37^oC results in the production of transformed or ectopic central nervous system structures in virtually all embryos. These include neuralised embryos, dramatically increased brain lobes and ectopic head ganglionic structures, as well as fused and enlarged ventral ganglia. These transformations are much less pronounced if the heat shock is carried out at stage 9-10, and are not seen if the heat shock is carried out later than stage 12.

Ectopic expression between 92 and 94 hours AEL allows almost complete rescue of the oc¹ mutant phenotype, longer heat shocks are required to rescue more medial head structures. Ectopic expression of P{hsp70-otd.R} between 92 and 94 hours AEL allows significant restoration of the en ocellar spot in at least 10% of discs.