Neurectodermal expression begins inembryonic stage 5 as discontinuous patches in several segments that laterextend and merge to form stripes the length of the embryo. The expressiondomain corresponds roughly to the dorsal half of the neurectoderm. Fromthis region, 4 S1 neuroblasts of the lateral column delaminate andenhancer trap expression is seen in all of these. This expression istransient and disappears by stage 9. At stage 10, expression is seen inmany dorsal S3-S5 neuroblasts and in their putative neurectodermalproneural clusters. Expression is also seen in some of their immediateprogeny. All are from the dorsal half of the neurogenic ectoderm but notall neuroblasts in this region show expression. Due in part to perdurance,EcollacZ expression is seen in many neurons and glia of stage 16 embryos.Some of these were identified as glial cells including six longitudinalglia, two cell body glia, some channel glia and some exit and peripheralglia.