Figure 8.

Comparison between the expression patterns of the Hoxb1/lacZ transgene in the randomly integrated version and at the three relocated positions (TgHb1, TgHb1^Del3, and TgHb1^Del7, from posterior to anterior, respectively, see Fig. 7). X-gal Staining of 10.5-d.p.c. fetuses are shown from a dorsal-anterior view. Expression in r4 was clearly detected in the TgNb1 (random) embryo (arrow), although absent from the relocated version (TgHb1; see Figs. 2 and 3). Moving the Hoxb1 transgene between Hoxd11 and Hoxd10 (TgHb1^Del3) did not modify this negative regulation as no staining was scored. However, moving the transgene more anteriorly (TgHb1^Del7) resulted in the appearance of a lacZ pattern in the hindbrain that was nevertheless restricted to a domain posterior to the r5/r6 rhombomeric boundary (arrow). Here again, staining in r4 was not observed. (ov) Otic vesicle; (fl) forelimb bud.