Enhancer trapexpression is first detected at stage 6 in the procephalic neurectodermand later in the delaminating neuroblasts of the ventral nerve cord. Atlater embryonic stages, the EcollacZ pattern is stated to be the same as thepattern of insc protein which is as follows. In stage 10, expression isdetected in two cells per segment in the lateral epidermis that arethought to be the first two cells that will give rise to the larvalperipheral sense organs. Expression is lost in developing sense organs bythe time of dorsal closure but remains in the CNS until after it hascondensed. In stages 10-13, expression is seen in mesodermal cellspresumed to be muscle precursors and in the posterior midgut primordia.Strong expression is seen at stage 15 in the pharynx, gastric caecae,hindgut, tracheal branches, and Malpighian tubules. In ovaries, enhancertrap expression is observed in nurse cell-associated follicle cells. Instage S9, there is expression in follicle cells covering the anterior partof the oocyte and by stage 10, in the centripetal cells at the borderbetween the nurse cells and the oocyte.