Fig. 6. Loss of zygotic Da leads to defects in allocation and patterning of heart
and somatic muscle. (A-F) Wild-type embryos; (G-L) da zygotic mutant
embryos. (A,B,G and H) show somatic muscles in embryos stained for Mhc. (G) An
example of more muscle in da zygotic mutant embryos: Lateral muscles
were duplicated as compared to wild-type. (H) Example of muscle loss. Muscle
VT1 is absent is some abdominal segments (white arrowhead), but is present in
others (black arrowhead). VT1 loss can be tied to loss of founder gene
expression. da embryos lack S59 (slouch) expression in the
cluster, which gives rise to this muscle (cluster I). Despite losses in S59
cluster I staining in many segments, not all VT1 muscles are absent. We
attribute this effect to low levels of S59 expression and/or expression of
other factors that allow formation of this muscle (J; arrowhead). (I) Ectopic
Eve expression in the anterior region of the mesodermal segment (arrowhead)
suggests a role for da in the allocation of somatic mesoderm.
Zfh1-positive pericardial and cardial cells and Fas III-expressing visceral
muscle progenitors were present in normal positions in the majority of
analyzed embryos (K,L), however absence of some Zfh1-positive cells can be
observed in some mutant embryos (arrowhead, K).
