Fig. 5. Absence of both maternal and zygotic Da function leads to loss of mesodermal tissues. (A-E) Wild-type embryos; (F-J) da maternal and zygotic mutant embryos. The somatic musculature failed to form in da holonull embryos. Most somatic muscles were missing, although oddly patterned multinucleated fibres were detected (F). Absence of Fas III positive visceral muscle progenitors and Zfh1 positive pericardial and cardial cells was observed in mutant embryos (G,H; arrowheads). Although the mesoderm does migrate, Twist levels were reduced or absent, shown here in stage 8 embryos (J) and in stage 10/11 embryos when subdivision of the mesoderm occurs (I; arrowhead).