The Wilms tumor genes wt1a and wt1b control different steps during formation of the zebrafish pronephros

Abstract

The Wilms tumor protein WT1 is an essential factor for kidney development. In humans, mutations in WT1 lead to Wilms tumor, a pediatric kidney cancer as well as to developmental anomalies concerning the urogenital tract. Inactivation of Wt1 in mice causes multiple organ defects most notably agenesis of the kidneys. In zebrafish, two paralogous wt1 genes exist, wt1a and wt1b. The wt1 genes are expressed in a similar and overlapping but not identical pattern. Here, we have examined the role of both wt1 genes in early kidney development employing a transgenic line with pronephros specific GFP expression and morpholino knockdown experiments. Inactivation of wt1a led to failure of glomerular differentiation and morphogenesis resulting in a rapidly expanding general body edema. In contrast, knockdown of wt1b was compatible with early glomerular development. After 48 h, however, wt1b morphant embryos developed cysts in the region of the glomeruli and tubules and subsequent pericardial edema at 4 days post-fertilization. Thus, our data suggest different functions for wt1a and wt1b in zebrafish nephrogenesis. While wt1a has a more fundamental and early role in pronephros development and is essential for the formation of glomerular structures, wt1b functions at later stages of nephrogenesis.

Renin expression in developing zebrafish is associated with angiogenesis and requires the Notch pathway and endothelium

“…Renin-expressing cells are also in contact with Wilms tumor 1b-expressing glomerular primordial cells (Fig. 1, F and G) (3,56), as also shown by Laing et al (43) and Hoshijima and Hirose (24) with podocin and ren ISHs.…”

“…Fish (Danio rerio) were maintained at 28.5°C, as previously described by Westerfield (75). Established lines used included WIK, casper (76), cloche (clo m39 ) (70), mindbomb (mib ta52b ) (30), Tg(kdrl:GFP) (10), Tg(kdrl:mCherry) (58), and Tg(wt1b:GFP) (56), where GFP is green fluorescent protein. Embryos were staged according to Kimmel et al (33) and anesthetized with 40 g/ml tricaine methanesulfonate.…”

Integration of Cistromic and Transcriptomic Analyses Identifies Nphs2, Mafb, and Magi2 as Wilms’ Tumor 1 Target Genes in Podocyte Differentiation and Maintenance

“…The injection of antisense morpholinos against nphs2, 37 mafba, and magi2 resulted in severe pericardial edema ( Figure 5, K-M), which is similar to what is seen in wt1a/b morphants. 39 To visualize potential glomerular defects in nphs2, mafba, and magi2 knockdown zebrafish embryos, we extended our experiments to the transgenic zebrafish line wt1b::GFP, which expresses GFP in the developing glomerulus and pronephric tubule. 39 At 48 hours postfertilization, the nphs2, mafba, and magi2 morphants displayed significant pronephros defects, which were visible as glomerular cysts ( Figure 5, N-U).…”

A Novel Wilms Tumor 1 (WT1) Target Gene Negatively Regulates the WNT Signaling Pathway

“…The experiment was repeated three to four times. For the analysis of zebrafish kidney, we used the wt1b::GFP transgenic zebrafish line with pronephros-specific green fluorescent protein expression (22). Embryos were raised at 28.5°C and staged according to Kimmel et al (23).…”

“…Given such high evolutionary conservation, we examined whether zebrafish wid might function in kidney development. To this end, we utilized a transgenic zebrafish expressing green fluorescent protein under the zebrafish wt1b promoter, wt1b::GFP (22), which expresses green fluorescent protein in the glomerulus and the pronephric tubule of developing pronephros. A splice antisense MO directed against the first splice acceptor site of wid (supplemental Fig.…”