Suppression subtractive hybridization analysis of gene expression during late kidney development identifies the developmentally regulated gene rPEA3.

BACKGROUND

While early kidney development has been studied exhaustively, the later stages of nephrogenesis that occur after birth in the rodent are relatively poorly understood. To gain insight into this process, we detected the alterations in gene expression in rat kidney at two postnatal stages, P0 (0 day after birth), the time at which nephrogensis is still active, and P21 (21 days after birth), when nephrogenesis is complete.

METHODS

Sprague-Dawley rats were mated, and appearance of a vaginal plug was designated as E0. Kidneys were dissected from embryos at E13, E15, E17 and E19, and from postnatal days P0, P7, P14, P21 and adult rats. Suppression subtractive hybridization (SSH) analysis was performed and highly expressed genes were evaluated as molecular markers by real-time reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization, immunofluorescence, and Western blot.

RESULTS

Several differentially expressed genes were identified, including rPEA3, a member of the PEA3 subfamily of Ets domain transcription factors. Real time RT-PCR analysis revealed that rPEA3 exhibited dynamic developmental regulation, with high levels of expression from embryonic day E15 until birth, and declining levels thereafter. By in situ hybridization, rPEA3 mRNA was detected in the ureteric bud (UB) and surrounding metanephric mesenchyme of the kidneys from E15 until birth, but was undetectable in mature kidneys. Double-immunofluorescence staining showed that both rPEA3 and WT1 expressed in the condensed mesenchymal cells at E15 and E17; and later from E19 to P7, both expressed in the epithelial cells of ureteric bud and their branches.

CONCLUSIONS

These studies provide compelling evidence that SSH is an effective method for identifying genes that are regulated during renal development, and suggest that the newly identified gene rPEA3 may play an important role in kidney development and differentiation.