Fig. 2. Early mesodermal expression of tin is sufficient to specify the dorsal mesoderm. Wild-type (left) and tin-null mutant embryos [homozygous for Df(3L)GC14] carrying the transgene tin-AB (right); (A-D) Lateral views; (E-H) Dorsal views. (A,B) Bin protein in visceral muscle progenitors of stage 10 control and tin mutant embryos carrying tin-AB. (C,D) Detection of bkh mRNA (green), Eve (red) and Tin (blue) protein. In late stage 11 control embryos (C), bkh-expressing cardioblasts (white arrowheads) and pericardial progenitors (red arrowhead, bkh⁺Eve⁺) are detected within the Tin domain. In corresponding tin-AB, tin mutant embryos (D), tin-AB-derived Tin has vanished but most bkh- and Eve-expressing cardiac progenitors are formed. (E,F) Staining for Odd, Zfh1 and Eve proteins identifies Odd-(Odd-pc, yellow) and Eve-pericardial cells (Eve-pc, pink) in stage 16 embryos. In the mutant (F), both types of pericardial cells are present, albeit arranged irregularly. The lymph gland (lg) is strongly reduced. (G) Mef2 staining of wild-type embryo at stage 16 (dv, dorsal vessel; sm, somatic musculature). (H) Mef2-expressing cardioblasts are present in tin-AB, tin^-, although at reduced numbers (arrowheads indicate interruptions in the dv, which can occur at variable AP positions).