The pax genes are a family of transcription factors that are active in specific tissues during early embryonic development. Pax family members possess a DNA-binding domain encoded by the paired box. Because paired domain containing genes encode transcription factors, they are capable of executing a genetic program. Several pax genes have also been associated with developmental mutations including: pax-3, which is associated with Waardenburg syndrome, pax-6, which is associated with Aniridia, and pax-2, which is associated with Wilms tumor. During embryogenesis, Pax-2 is expressed in the developing kidney. In particular, the pax-2 gene is expressed in condensing metanephric mesenchyme and in early epithelial structures derived from mesenchyme; however, pax-2 mRNA and protein levels are rapidly down regulated as the tubular epithelium matures. Although Pax-2 is down regulated during renal epithelium maturation, Pax-2 expression persists in the undifferentiated epithelium of Wilms' tumors. Persistent expression of Pax-2 in Wilms' tumors occurs frequently and correlates with the proliferation of poorly differentiated epithelial cells in these tumors. Interestingly, expression of the Wilms' tumor suppresser protein, WT1, coincides with down-regulation of the pax-2 gene; thus, suggesting that WT1 can directly repress pax-2 transcription.
optic disc coloboma; paired box gene 2; paired box homeotic gene 2; Paired box protein Pax-2