Fig. 4

Specification of the Ventral Head Muscles Requires Tcf21 Activity

(A–X′) Live images and schematic diagrams of embryos of indicated stages and genotypes carrying the indicated transgenes. In mutants, most muscles expressing tcf21 are absent or severely reduced (A–H, C′, D′, G′, H′). Extraocular muscles (arrows in E–H) and sternohyoideus muscles (asterisks in E–H, G′, H′) do not express tcf21 and are not affected in tcf21 mutant embryos. Arrowheads in (R)–(T) and (V)–(X) indicate the HA, and numbers indicate pPAAs 3–6. Note that the HA is formed incompletely in the tcf21 mutant embryos (V, X, X′). The light green color in (K′) and (L′) marks the nkx2.5+ head muscles. The nkx2.5+ endothelial cells are indicated by dark green. Lateral views (first, third, and fifth column) and ventral views (second, fourth, and sixth column). Sample number of imaged embryos is indicated as a total for the ventral and lateral views.