Figure 4. VAB-10 antibodies recognize regions of epidermis-muscle contact. Confocal projections of embryos stained with antibodies against VAB-10A (4F2: A, C, and E; MH5: B and D) or VAB-10B (K22: F, G, I, and J; K32: H, K, and L), and with the mAbs MH46 (recognizes myotactin at the basal epidermal membrane in regions of muscle contact; A, F, and I), NE8/4C6 (K, muscle-specific), or MH27 (D, adherens junction-specific; staining with mAbs is in red). (A and F) Early wild-type comma embryos; VAB-10A and VAB-10B staining is detected at the basal (b) and apical (a) membranes as further shown in optical cross sections along the apico-basal axis at the level of arrows (3x insets surrounded by a dotted line). (B and C) Wild-type embryo revealing three muscle-epidermis contact areas. (D and E)
vab-10(
h1356) embryo (arrow) and a neighboring heterozygous sibling (right); the VAB-10A signal is absent in the
h1356 mutant embryo even at a stage when muscles are not yet functional (MH27 staining reveals that fusion between dorsal epidermal cells (dots), which normally precedes the first muscle contraction, did not occur yet; arrowheads show two areas of muscle contact in the control). (G and H) Wild-type embryos revealing two muscle-epidermis contact areas, the pharynx and the intestine (arrowhead). (I and J)
vab-10B(
mc44) embryo (arrow) and a neighboring heterozygous sibling (bottom); there is a very faint residual staining with K22 antibodies. (K) Z-optical projection through the entire stack of images for the embryo in H at the level of the white bar; VAB-10B is found above muscles (in red) and in the intestine (arrowhead). (L)
vab-10B(
mc44) embryo (arrow) and a neighboring heterozygous sibling (bottom); there is essentially no staining with K32 antibodies. Bars, 10 um.