Fig. 7. A model for the progression of proneural wave. Schematic horizontal sections as in (Fig. 1C, Fig. 2G). JAK/STAT signaling is activated in the NE cells and its activation is high in the lateral and low in the medial side of NE. As the NE cells proliferate, Upd-expressing NE cells move laterally, and so does the activation of the JAK/STAT signaling. Medial NE cells freed from negative regulation of JAK/STAT signaling express L(1)sc and proneural wave moves laterally.