Figure 4. VAB-2/EFN-1 Is Expressed in Neurons Adjacent to VAB-1-Expressing Cells. Confocal images of VAB-2/EFN-1 expression from the juIs53 [
vab-2/efn-1(+)] transgene, visualized using anti-VAB-2/EFN-1 antibodies (green); epidermal adherens junctions were visualized using the MH27 monoclonal antibody (red); VAB-1::GFP expression in (D)-(F) visualized with anti-GFP antibodies (blue). Bar, 10 μm (A, B, D-H), 20 μm (C).(A and B) Ventrolateral and ventral views of early enclosure. During epidermal enclosure VAB-2/EFN-1 is expressed in many neurons in the anterior and in several in the tail. Based on double staining with the epidermal markers MH27 and LIN-26, VAB-2/EFN-1 is not expressed in epidermal cells or precursors. Leading epidermal cells (arrows) appear to migrate directly over VAB-2/EFN-1-expressing neurons.(C) Late embryo, 3-fold stage; the nerve ring (arrowed), head neurons, and dorsal and ventral nerve cords express VAB-2/EFN-1. Strong expression is also seen in the metacorpus, isthmus, and valve regions of the pharynx.(D) Triple label immunofluorescence (confocal section) showing VAB-2/EFN-1 (green), VAB-1::GFP (blue), and MH27 (red). Lateral view during early enclosure; leading edges of epidermal cells are arrowed.(E and F) VAB-2/EFN-1 and VAB-1::GFP expression after leading cells have met at the ventral midline (arrow). Ventral views; (E) is a confocal section showing only VAB-2/EFN-1 and VAB-1::GFP channels; (F) is a confocal projection of the ventral half of the embryo in all three channels. VAB-1::GFP and VAB-2/EFN-1 expressing cells form distinct, adjacent populations.(G and H) VAB-2/EFN-1 expression in
vab-1(
e2) mutant embryos. VAB-2/EFN-1-expressing cells become more spread out, compare brackets showing extent of VAB-2/EFN-1 staining in (A) and (B) versus (G) and (H). Spreading of VAB-2/EFN-1-expressing cells was seen in 70% (135/192) of
vab-1(
e2) embryos. Mild spreading was seen in 33% (12/36) of control juIs53 embryos.