Fig. 5. (A-C) Expression pattern of the proneural gene CsASH1 and the neural HRP antigen after injection of CsDelta2 and CsNotch dsRNA. Light micrographs of flat preparations of the second to fourth opisthosomal segments; anterior is towards the top. (A) At about 180 hours, CsASH1 is expressed in a medial stripe and a patch of cells in the lateral region of the opisthosomal hemisegments (arrows). This pattern is unchanged after injection of GFP dsRNA. (B,C) In embryos injected with CsDelta2 dsRNA (B) and CsNotch dsRNA (C), a strong upregulation of CsASH1 expression can be observed (arrows), while after injection of CsDelta1 only a minor change in the expression pattern is visible (data not shown). (D) The anti-HRP antibody stains the cell processes of the invaginating cells (arrow) in an embryo injected with GFP dsRNA as a control. (E) After injection of CsNotch dsRNA, the HRP antigen is upregulated in the apical cells. A stronger staining (arrow) is visible in the regions where invagination sites normally form (compare with Fig. 3J). (F) Higher magnification of a neuroectodermal region, where no invagination sites have been formed after injection of CsDelta2 dsRNA. Apical located cells are stained with the anti-HRP antibody (arrow). o2-o4, opisthosomal segments 2 to 4. Scale bars: in A, 100 µm for A-C; inD, 50 µm for D,E; in F, 20 µm for F.

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