Figure 6.

Ectopic Hoxd13 expression and concurrent phenotypic alterations. (A) Hoxd13 expression in wild-type (left) and TgHb1 (right) 10.5-d.p.c. fetuses. Expression patterns were identical to each other in limb buds. In addition, the signal was restricted to the posterior part of the trunk for both wild-type and TgHb1 embryos. However, expression in the latter embryo was slightly anteriorized (arrows). (B) Adult skeletal preparations showed that all animals carrying the relocated transgene (TgHb1) displayed five lumbar vertebrae (left), instead of the six found among control littermates (right). (C) Expression of Hoxd13 in 11.5-d.p.c. fetuses carrying the relocated Hoxd9/lacZ transgene, either in the presence (TgHd9neo+, left) or in the absence (TgHd9, right) of the PGK-neo selection cassette. No obvious ectopic Hoxd13 expression was detected in the left fetus, which showed signals in the tip of developing limb buds and in the emerging genital eminence. After excision of the neo cassette, however, strong expression was de tected throughout the posterior part, including in somitic (black arrow) and intermediate (white arrow) mesoderm. This latter domain included the metanephric blastema, as verified by histological sections (not shown). (D) Dissected urogenital system of newborn animals carrying the Hoxd9/lacZ transgene relocated upstream Hoxd13, with (left) or without (right) the PGK-neo selection cassette. In the absence of the neo gene, kidneys were not formed (arrows), whereas truncated ureteres of variable lengths could be observed at the expected position.