Fig. 4. Hemiadherens junctions are defective in embryos lacking the glide complex. (A) Schematic representation of an attachment site at late stage 16. Actin microfilaments and microtubules (MTs) are present in muscle fibres and in tendon cells, respectively, and are connected to hemiadherens junctions (HAJs). Attachment between muscle and tendon cell is formed by the adhesion of HAJs to extracellular matrix components (visualised by an electron-dense material) (modified from Subramanian et al., 2003). (B,C) Electron microscopy analysis of muscle attachment site in wild-type (B) and glide-glide2 late-stage 16 to early-stage-17 embryos (C). M and TC indicate the muscle fibre and the tendon cell, respectively. (C) Note that the electron-dense material is absent in the mutant and that muscle fibre and tendon cell membranes can be easily identified instead of being tightly interdigitated as in the wild type (B). (D-I) Anti-myosin (green) and anti-ßPS integrin (red) co-labelling reveal muscle attachment site organisation in stage-17 embryos of the following genotypes: (D-F) wild-type (WT), (G-I) glide-glide2 embryos. All panels show ventral views, anterior to the top. ßPS integrin accumulates at the ends of wild-type muscles. (G-I) Note the weak accumulation at the position of normal sites (arrowhead in G) and the ectopic accumulation at muscle terminals abutting each other at the ventral midline (arrow in G). Ventral midline is indicated by dashed line in F,I. Scale bars: 1 µm in B,C; 50 µm in D-I.