EcollacZ is expressed in the ventral midline. The EcollacZ expression pattern of this line is in good agreement with wild type sli transcript and protein expression. sli is first detected during gastrulation. At germ band extension, midline mesectodermal cells express sli. During germ band retraction, sli is detected in the 6 midline glial cells derived from the midline neurepithelium. During dorsal closure, sli expression is detected in cardioblasts, walls of the gut, and near the muscle attachment sites in the ectoderm.