The expression pattern of the EcollacZ^CaBP1-12A8 enhancer trap resembles that of the 1.6 kb CaBP1 transcript. In syncytial blastoderm embryos, the reporter is detected at the poles. At cellular blastoderm, this expression is replaced by wide stripes. After gastrulation, EcollacZ is detected in the ventral midline precursors, and the posterior head. Midline expression continues through the rest of embryogenesis, in clusters of cells in each CNS segment. Some, but not all of these clusters correspond to VUM neurons. During germ band extension, weak dorsoventral stripes of expression are also seen.