Abstract 1423: Transcription induced by the POU6F2-encoded RPF-1 and genome-wide screening of promoter occupancy unveil a potential regulatory role in kidney embryogenesis
Authors: Fiorino Antonio , Gamba Beatrice , Bucci Gabriele , Manenti Giacomo , Radice Paolo , Perotti Daniela 
Published: August 2012

Abstract
Wilms Tumor (WT, or nephroblastoma), a tumor of embryonic origin, is the most frequent genitourinary tumor in childhood. Current view of this malignancy point out to a common origin with the fetal developing kidney. Undifferentiated mesenchymal cell types and differentiated immature structures are in fact present in WTs, whose gene expression tend to overlap with the early nephrogenesis transcriptome. Remarkably, several factors guiding the development of kidney are overexpressed in WT specimens. WT is also characterized by alterations at several genomic loci and 20% patients exhibit LOH at chr7p. We were able to identify the smallest overlapping region at 7p14 encoding the POU6F2 gene, of the POU family of transcription factors regulating developmental and biological processes. Moreover, expression of POU6F2 mouse homolog was shown during nephrogenesis. These finding may be indicative of a role for this gene in kidney development, and since perturbation of this process contribute to WT, we addressed whether the Retina-derived POU domain Factor-1 (RPF-1, product of POU6F2) is a bonafide transcription factor participating in the transcriptional program that drive nephrogenesis. By addressing RPF-1 protein-DNA interaction we could confirm functional interaction with consensus octamers for POU proteins. Following its induction in human embryo kidney (HEK293) stable transfectants, the pattern of transcriptional targets regulated was evaluated and about 750 genes showed significant modulation (p&lt;0.01) by its expression. Further, genome-wide localization of RPF-1 bound promoter regions via ChIP-chip enabled identification of loci in approximately 1,700 genes. Overlapping with the transcriptome showed a set of 367 genes directly modulated through its expression. Motif analysis at their loci indicated the presence of degenerate POU octameric sequences in &gt;80% genes, suggesting for RPF-1 a low specificity in its binding to DNA. Top biological processes emerging from functional annotation analysis of direct transcriptional targets included kidney, metanephron, tube and ureteric bud development, primary germ layer formation, cell fate commitment, and neurogenesis as well. Axonal guidance, ephrin signalling, and transcription were top canonical functions clustered by gene ontology. Accordingly, regulators of nephrogenesis, such as EYA1, PDGFD, SLIT2 and ROBO2, myogenic differentiator MEF2C, neurite regulator MAP2, and GATA2 stem cell differentiator, are all regulated through promoter featuring closely spaced octamers. Overall, our results suggest a direct implication of RPF-1 into the transcriptional program guiding kidney development, and perturbation of its function during embryogenesis may contribute to the development of nephroblastoma.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1423. doi:1538-7445.AM2012-1423