Fig. 2. pnr and ush are required for myocardial and pericardial cell formation. (A-L) tin expression. (A-D) Mid-stage 11. (A) Wild-type embryo expressing tin segmentally in two clusters of cells. The dorsal clusters (arrow) correspond to the cardiac precursors and the lateral clusters (arrowhead) correspond to visceral mesoderm. (B) pnr mutant embryo exhibiting normal tin expression only in the lateral clusters (arrowhead), but not in dorsal clusters (arrow). (C) ush mutant expressing tin normally. (D) Histogram of tin expression in the heart progenitors of pnr and ush mutants at mid-stage 11. (E-H) Late-stage 11. (E) Wild-type embryos expressing tin in the cardiac mesoderm. (F) pnr and (G) ush mutants exhibiting a reduction in tin expression (arrow). (H) Histogram of tin expression in the heart progenitors of pnr and ush mutants at late-stage 11. (I-L) Stage 13 embryos. (J) pnr and (K) ush mutants exhibiting reduced tin expression (arrow). (L) Histogram of tin expression in the heart progenitors of pnr and ush mutants at stage 13. (M-P) Late stage 11 embryos stained for Eve. (M) Wild-type embryo expressing Eve in 11 clusters of cells. (N) In pnr mutants, the number of Eve cells is reduced (arrow). (O) In ush mutants, Eve stained cardiac clusters are indistinguishable from wild type. (P) Histogram of Eve expression in late stage 11 pnr and ush mutants. (Q-T) Stage 13 embryos stained for Eve (red) and Lbe (green). (Q) Wild-type embryo. (R) pnr mutant embryo exhibiting dramatically reduced Lbe staining and moderately reduced Eve staining (arrow). (S) ush mutant embryo exhibiting near normal amounts of Lbe and Eve staining, although the segmental pattern is perturbed (compounded by defects in germ band retraction). (T) Histogram of Lbe expression in stage 13 pnr and ush mutants. (U-X) Stage 13 embryos expressing svp RNA in the cardiac mesoderm (indicated by arrows). (U) Wild type. (V) pnr and (W) ush mutant embryos exhibiting severely reduced svp expression in the heart. (X) Histogram of svp expression in stage 13 pnr and ush mutants. (Y₁-Z) Dorsal view of stage 16 embryos stained for the late pericardial cell marker Pericardin (Yarnitzky and Volk, 1995; Chartier et al., 2002). pnr, ush and raw mutants do not complete dorsal closure. (Y₁) Wild type. (Y₂) pnr and (Y₃) ush mutants exhibiting a severe decrease in pericardial cells (arrowheads). (Y₄) Histogram of Pericardin expression in stage 16 pnr and ush mutants. (Z) Dorsal open raw mutant exhibiting an excess in pericardial cell staining.