Repression of Pax-2 by WT1 during normal kidney development

Area of Science:

• Developmental biology
• Molecular genetics
• Cancer research

Background:

• Pax-2 is a developmental gene critical for kidney morphogenesis, activated early and repressed in mature kidney cells.
• Persistent Pax-2 expression is noted in various kidney tumors, but its regulatory signals in development are unclear.
• Wilms tumor suppressor protein (WT1) is implicated in kidney development and cancer.

Purpose of the Study:

• To investigate the signals regulating the transient expression of Pax-2 during kidney development.
• To determine the relationship between Pax-2 and WT1 expression patterns in the developing kidney.
• To elucidate the mechanism by which WT1 might regulate Pax-2 transcription.

Main Methods:

• Examined spatial and temporal expression of Pax-2 and WT1 using specific antibodies in developing mouse kidneys.
• Performed DNAseI footprinting to assess WT1 binding to Pax-2 regulatory elements.
• Utilized co-transfection assays with CAT reporter constructs to evaluate WT1-dependent transcriptional repression of Pax-2.

Main Results:

• Increased WT1 protein levels correlated with decreased Pax-2 gene expression in visceral glomerular epithelium precursor cells.
• WT1 demonstrated direct binding to high-affinity sites within the Pax-2 5' untranslated leader sequence.
• WT1 mediated transcriptional repression of Pax-2, both through its native regulatory sequences and when inserted into a heterologous promoter system.

Conclusions:

• Pax-2 is identified as a likely direct transcriptional target of WT1.
• A direct regulatory link exists between the developmental gene Pax-2 and the tumor suppressor gene WT1.
• This interaction suggests a mechanism involving WT1 in controlling Pax-2 expression in both normal kidney development and tumorigenesis.