Fig. 7. Summary diagram of molecular markers expressed in brain NBs at different stages of embryonic development. Colour code indicates the expression of more than 40 different molecular markers (representing 34 different genes as listed) in individual brain NBs. In addition to the markers described in this paper, these maps include the expression of the proneural, segment polarity, DV patterning and glial marker genes, a detailed description of which is given in the accompanying papers (Urbach et al., 2003; Urbach and Technau, 2003). Each brain NB expresses a specific combination of molecular markers. Accordingly, each NB can be uniquely identified at stage 9 (A; st9), stage 10 (B; st10) and stage 11 (C; st11, which is when the entire population of brain NBs is established). Red lines indicate the neuromeric boundaries between the trito- (T) and deutocerebrum (D), and the ocular (Oc-P) and labral protocerebrum (Lr-P). Anterior (a) is towards the top; dorsal (d) is towards the left. CL, clypeolabrum; FG, foregut.