Fig. 4. Regulation of hb within the thoracic NB2-4T lineage. Embryos are double labelled for the NB2-4T lineage marker Eg (magenta) and Hb (green). NB2-4T-derived cells are outlined; midline is towards the left. Insets show Eg expression separately. (A-C) Wild type. At early stage 11 NB2-4T has divided once to give rise to the Hb⁺ GMC2-4Ta (A). At early stage 12 the NB has generated three GMCs, two of them are the first-born Hb⁺ GMC2-4Ta and GMC2-4Tb (B, arrowheads). At stage 14, four neurons are Hb⁺, which are the progeny of the two first born GMCs (C, arrowheads). (D-F) svp^e22. Hb expression is not downregulated after the second mitosis (E), resulting in up to eight Hb⁺ neurons (F, arrowheads). (G-I) pros^C7. Hb is initially expressed in the first and second born GMCs (H, arrowheads), but the expression is often not maintained in one GMC (most likely GMC2-4Tb), resulting in only two Hb⁺ neurons at stage 14 (I, arrowheads). (J) Scheme of early NB2-4T lineage development with markers used in our analysis. Scale bar: 20 µm.