Fig. 3. Shot associates with E-cadherin and is required for adherens junction development in selected cell types. Anterior, leftwards; dorsal, upwards. E-cadherin, red; Shot, green. (A-C) Dorsal trunk tracheal cells in a stage 14 wild-type embryo form adherens junctions associated with Shot. (A) E-cadherin forms a web of junctions that gird the apical surfaces of tracheal cells, joined at segment boundaries (arrowhead). Scale bar: 10 µm in A-C. (B) Shot concentrates at adherens junctions. (C) Merge of A and B. (D-F) Lateral chordotonal (lch) neurons form highly organized adherens junctions with support cells. (D) In a stage 15 wild-type embryo, E-cadherin clusters in two rows of adherens junctions (arrowheads) formed by support cells contacting chordotonal dendrites. The arrow indicates neuronal cell bodies, which do not express E-cadherin. Scale bar: 10 µm in D-L. (E) Shot colocalizes with E-cadherin in the dorsalmost set of adherens junctions associated with lch neurons. (F) Merge of D and E. (G-I) Shot does not appreciably colocalize with epidermal adherens junctions. (G) Cadherin distribution at the dorsal midline (long arrow) of a stage 15 wild-type embryo. This section is taken 1 µm below the section where most E-cadherin is observed, and 1 mm above where most Shot can be detected. (H) Shot distribution in the same optical section. Shot is relatively diffuse, except in spots where it colocalizes with E-cadherin (short arrows). (I) Merge of G and H. E-cadherin and Shot overlap weakly. (J-L) E-cadherin and Shot distribution in shot³ null mutant embryos. (J) Cells in the dorsal tracheal trunk of a stage 14 shot³ mutant embryo. The branches fail to fuse at the segment boundary (arrowhead), and Shot is absent in all cells. E-cadherin appears normal in tracheal cells other than fusion cells. (K) E-cadherin contacts with chordotonal neurons in a stage 15 shot³ mutant embryo are abnormally organized and shaped. (L) E-cadherin contacts between epidermal cells appear normal at the dorsal midline (long arrow) in a stage 15 shot³ mutant embryo, including stereotyped spots where it colocalizes with E-cadherin (short arrows).

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