Figure 3. Dependence of Tg expression upon MEF2.

Tg transcription (A, B) and Tg-lacZ expression (C, D) were robust in the dorsal vessel of wild-type (A, C), but absent in Mef2 mutants (B, D). Note that Tg expression in the sub-pharyngeal region was not affected by the absence of MEF2 (insets in A, B). Tg transcripts in A and B were visualized either using fluorescent in situ hybridization and detected by confocal microscopy, or by immunohistochemical staining following in situ hybridization (insets). Tg-lacZ expression was detected in C and D via immunofluorescence for ß-galactosidase protein (green), and the location of the dorsal vessel was demonstrated by immunofluorescence for the pericardial cell marker Pericardin (red). Tg transcription (E, F) and Tg-lacZ expression (G, H) were also detected in either wild-type embryos (E, G) or those in which ectopic Mef2 expression had been induced (F, H). In this experiment, only mild ectopic activation of the target gene was observed in the head regions of embryos (arrows in F and H). Embryos are oriented with anterior to the left. A-D are dorsal views; E-H and insets are sagittal views. Bar, 100μm.