Fig. 4. abd-A^MX1 homozygotes show no heart formation. Homozygous abd-A mutants were identified based upon a lack of reactivity to anti-ABDA antibody, or based upon abnormal morphology of the gut, and then stained for expression of the indicated genes. Small arrows bracket the cells that, in wild-type, would form the heart. (A) Anti-MEF2 staining demonstrated a lack of dorsal closure in the mutants. (B) Hand was expressed in the two rows of dorsal vessel cells; however, most cells had a uniform size and shape (compare with Fig. 3B, where the heart cells assumed an unique shape). (C,D) MHC accumulation in the dorsal vessel cells; once again, cell shape and levels of MHC accumulation along the length of the dorsal vessel were uniform. (E) Tina-1 was not expressed in the dorsal vessel (one row of dorsal vessel cells in the presumptive heart forming region is indicated by dv), although expression in the hindgut (hg) was unaffected. Scale bars: 50 µm for A-C,E; 25 µm for D. All micrographs are dorsal views of stage 16 (or equivalent) embryos with anterior towards the left.

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