Fig. 1. Ubiquitous expression of mouse and Drosophila Tsh genes provokes identical homeotic transformations in the Drosophila embryo. (A) Ubiquitous mouse Tsh1 and ectopic Tsh proteins expressed by the 69B-Gal4 driver in wild-type embryos accumulate in the nucleus of epidermal cells. Confocal section through the nucleus of the epidermis of the head/thorax region of stage 12-13 69B>tsh and 69B>Tsh1 embryos. The localization of Tsh proteins is shown in green and the nuclei are stained by propidium iodide (red). (B) Comparison of the mouse Tsh proteins level upon ectopic expression in 69B>Tsh Drosophila embryos by western blot analysis with an anti-c-Myc antibody. Two independent transgenic lines are shown for mouse Tsh1, 2 and 3. Mod expression levels serve as a loading control. (C) Wild-type larval cuticle (dark field, left) and close-up (phase contrast, right) of the trunk-head region showing the T1 segment and its beard (b). (D) Ectopic tsh expression with the epidermal 69B-Gal4 driver (69B>tsh) at 18°C showing the homeotic transformation of the labial head segment into the first thoracic segment. Arrows indicate the beard in the ectopic T1 segment, most visible on phase contrast pictures. Head involution is affected and most of the head skeleton is deleted; compare with C. (E-G) Labial to T1 homeosis induced by the three Tsh genes. (E) 69B>Tsh1, (F) 69B>Tsh2 and (G) 69B>Tsh3 cuticles of larvae raised at 29°C. All the Tsh-expressing larvae are affected. Arrowheads indicate ectopic denticles resulting from the transformation of more anterior head segments into trunk (shown for tsh and Tsh1, similar result for Tsh2 and Tsh3 but out of focus, data not shown). Anterior is towards the left and dorsal on the top. T1, T1 thoracic segment.