Fig. 6. JAK/STAT signal negatively regulates the progression of proneural wave. (A-A'') Loss of Stat92E function lead to earlier progression of proneural wave and NB development. Stat92E^85C9 clones were shown by the absence of GFP (blue). (A') Enlarged view of square in A. Clones were circled by yellow lines. Broken white line indicates border between NE and NB. White arrows show earlier (more lateral) expression of Dpn (magenta) and L(1)sc (green). L(1)sc was ectopically expressed in the M(3)^w124/+ cells next to the clones (white arrowheads). (A'') Projection of XX stacking confocal planes including A. Yellow arrows show earlier expression of Dpn (magenta) and L(1)sc (green). (B,B') Ase (magenta) was expressed in more lateral cells and ectopic neurons (Elav, blue) were observed associated with the Stat92E⁶³⁴⁶ clones. The clones are shown by the absence of GFP (green) in B and yellow line in B'. (C-C'') JAK/STAT signal regulates the number of lamina neurons and medulla NBs. Stat92E^85C9 clones are shown by the absence of GFP (green; circled by a yellow line in C'). (C'') Projection of XX stacking confocal planes including C. In and around the Stat92E^85C9 clone, putative lamina cells [marked by Dac (blue)] were replaced by medulla NBs [marked by Dpn (magenta)], so that the lamina region was reduced in contrast to the normal optic lobe (arrow in C'', compare with Fig. 1D or Fig. 5C). (D,D') L(1)sc (green) and Dpn (magenta) remained more medial; nearby cells expressing hop^Tum-l are marked by the expression of GFP (blue) or arrowhead in D'. (E,E') Expression of Arm (blue) remained in the hop^Tum-l-expressing clone. Clones were marked by the expression of GFP (green) and NBs by Dpn (magenta). (F,F') L(1)sc (green) and Dpn (magenta) remained more medial; nearby cells expressing upd are marked by the expression of GFP (blue) or arrowhead in F'. (G,G') Expression of Arm (blue) remained near the upd-expressing clone marked by GFP (green). NBs were marked by Dpn (magenta). (H) Summary of loss-of-function and gain-of-function mutation of the JAK/STAT signal. Proneural wave extends more medially with elevated JAK/STAT signaling and laterally with decreased signaling. Clones are within the black lines. NBs (magenta), L(1)sc-expressing cells (green) and NE cells (blue) are shown. (I) A model for the ordered formation of NBs in medulla development. JAK/STAT signaling negatively regulates the progression of the proneural wave, which induces NB formation and hence regulates the number of medulla NBs.