A EcollacZ construct driven by 1.6 kb ofsna upstream sequence is expressed in the precursors and postmitoticneurons of the PNS, but not in the CNS.
A 1.6 kb sna promoterregion drives EcollacZ expression in a narrower band of cells than seen in wildtype sna transcript expression (12 rather than 18 cells). No expression isseen in the poles.
Expression is activated by peak levels of dl protein present in the ventral-most 12 cells of early embryos.