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. Author manuscript; available in PMC: 2014 Sep 1.
Published in final edited form as: Wiley Interdiscip Rev Dev Biol. 2013 Feb 11;2(5):701–721. doi: 10.1002/wdev.111

Figure 2. The proneural-neurogenic gene network controls NB patterning.

Figure 2

(A) Lateral view of Drosophila embryo prior to NB delamination. Expression of the prepatterning factors which trigger proneural gene expression is indicated by coloring. Along the antero-posterior axis, Vnd, Ind, and Msh are expressed in the medial, intermediate, and lateral column of the neurectoderm, respectively; segment polarity genes and pair rule genes (represented by Ftz and Odd) define transverse domains in each segment. (B) Photograph showing ventral view of medial neurectoderm (mVN: medial column); proneural clusters expressing ac are labeled brown; purple stripes indicate expression of segment polarity gene engrailed (from20). (C) Schematic cross section of neurectoderm, indicating pattern of proneural clusters (purple shading). Rectangle indicates frame shown in panel (E). (D) Artistic rendering of proneural cluster before (top), during (middle), and after NB delamination (bottom; from4). (E) Lateral inhibition within proneural cluster mediated by N, Dl and E(spl) genes. (F) Two-step model of NB specification. Expression of proneural genes defines proneural clusters (top); lateral inhibition in each cluster selects NB (bottom).