Fig. 5. Nab is a co-activator of Sqz in embryonic CNS development. (A,B) Ventral (A) and lateral (B) views of stage-17 Drosophila embryos showing nab (red) and sqz (green) expression patterns. (A',B') Magnified views of the segmental pattern showed in A,B. (C,C') Stage-17 embryo stained with antibodies to Ap (red) and Nab (green). Three cells in the ap cluster express nab (C', a magnified view of the T1 segments), one of them showing stronger expression. (D,D') First instar larvae stained for Ap (red), Nab (green) and FMRFa (blue). Only the Tv neuron, detected by anti-FMRFa staining, expresses nab in the ap cluster (D', a magnified view of the T1 segments). (E,E') nab first instar larvae showing expression of ap (red), dimm (green) and FMRFa (blue). More cells occupy the ap cluster (T3 on the right is out of focus), FMRFa expression is mostly lost and is present only in T3, and additional cells express dimm (E', a magnified view of the T1 segments). (F) The larval CNS. The green square indicates the area shown in D and E, the red square the area shown in G and G'. (G,G') Wild-type (G) and nab mutant (G') second instar CNS showing FMRFa expression. In all panels, arrows indicate the first (T1) thoracic segment and arrowheads the second (T2) and third (T3) thoracic segments. (H,I) Averages (x) and s.d. (d) of the number of cells that express ap and dimm (H) and FMRFa (I) in the T1 segments of wild-type, sqz^lacZ and nab^SH143 embryos; n, number of larvae scored; ^*, data from Allan et al. (Allan et al., 2005).