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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.
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