June 1, 1996;
Wilms' tumor suppressor gene is involved in the development of disparate kidney forms: evidence from expression in the Xenopus pronephros.
The Wilms'' tumor suppressor gene (WT1
) is required for the formation of the mammalian metanephros, or adult kidney
, and for the normal development of the mesonephros
, the major mammalian embryonic kidney
. In this report the isolation of a Xenopus gene closely related to the mammalian WT1
gene in both sequence and splicing pattern is described. Expression of this gene, xWT1
, is restricted to the developing nephric system until late tadpole
stages, which expression also begins to be observed in the heart
. Within the nephric system, expression is observed in the dorsal portion of the splanchnic lateral
plate in tailbud
embryos, and in the glomus
of early tadpoles. No expression is observed in the pronephric tubules or pronephric duct
. The WT1
gene is therefore expressed in a similar temporal and spatial pattern in the vascularized portion of the amphibian pronephroi and in the mammalian metanephroi, arguing that it probably plays a similar crucial role in the morphogenesis of these very different kidney
forms. The absence of expression in the developing pronephric tubules indicates that xWT1
is not required for the epithelialization of the tubular portion of the pronephros
[+] show captions
wt1 (WT1 transcription factor) gene expression in Xenopus laevis embryo via in situ hybridization, NF stage 24, lateral view, anterior left, dorsal up.
Fig. 3. In situ hybridization of xWt1 to Xenopus embryos. The embryos are not cleared. Except in A and C, which are dorsal views with anterior to the left, all panels are lateral views with anterior to the left. A: Stage 20. The white arrows indicate xWTf specific staining. 6: Stage 23-24 embryo. C: Stage 23-24 embryo dorsal view. D: Stage 27-28 embryo. The white arrow indicates xWt1 staining. E: Stage 30 embryo. F: Enlargement of the pronephric region of panel E (boxed). G: Stage 39
embryo, close-up of the head region. Note the small blue patch of stain behind, and much smaller than the pronephros itself. This corresponds to
the glomus (red arrow). The black arrow indicates heart staining. H: Pronephric tubules of a stage 36-37 tadpole visualized by staining with monoclonal antibody 3G8. Note the difference between the position and shape of the tubules (red arrow, H) and the glomus (red arrow, G).
Fig. 4. A: Transverse section through a stage 28 embryo previously stained for xWt1 expression via in situ hybridization. Note the expression throughout the splanchnic lateral plate adjacent to the pronephric anlage. B: Transverse section through a stage 30-31 embryo previously stained for xWt1 expression via in situ hybridization. Expression is observed in the dorsal aspect of the splanchnic lateral plate. C: Sketch indicating the anatomical features of the section shown in 6.