Fig. 4.

Tup expression requires the presence of early cardiac transcription factors and depends on wg and dpp signaling. (A-D) Tup expression is initiated in the cell clusters in Drosophila tin³⁴⁶ mutants (arrowheads in B) but is not maintained at later stages (compare C with D). (E) Myocardial Tup and Dmef2 expression is absent in Df(3L)DocA mutants. Since Doc mutants have been shown to also lack pericardial cells, the remaining Tup-expressing cells (green) are unlikely to be cardiac-related cells. (F) pnr^VX6 mutants also show a dramatic reduction in myocardial Tup- and Dmef2-expressing cells. (G,H) Tup expression at stage 13/14 depends on Wg (G) and Dpp (H) signaling. Arrowheads in all images point to Dmef2/Tup co-expressing cells, which appear yellow in the merged optical sections. Asterisks are placed in the region of the myocardial cell row, which has defects to various degrees in all mutants shown.