Profiling Of Potential Ppar Target Genes In Mouse Aorta

Diminished activity of the transcription factor PPAR gamma (PPARγ) has been suggested to play a role in hypertension and vascular dysfunction. The downstream actions of PPARγ, like other transcription factors, depend on binding to a specific DNA sequence and then activating/repressing transcription of target genes. We recently demonstrated using microarray analysis that chronic activation of a PPARγ agonist elicits changes in numerous pathways (181 genes) in mouse aorta. To prioritize this list of genes so that experimental efforts are directed toward the best candidates, we used a computational approach to screen the regions upstream of 142 of these genes for binding sites for PPARγ and for two transcription factors regulated by PPARγ, hypoxia-inducible factor 1 (HIF), and BHLHB2. All upstream sequences (5 kb) were downloaded from Ensembl. We found numerous binding sites for PPARγ (117), HIF (490), and BHLHB2 (105). Because sequences that are highly conserved among different species are likely to be enriched for biological important sequences, we then obtained local alignments across human and mouse species. This allowed us to reduce the number of potential binding sites (and target genes) to less than 10 (PPRE=2, HIF=6, and BHLHB2=1). These high priority candidate PPARγ target genes include frizzled 4 (FZD4), BHLHB2, clusterin, and secreted frizzled related protein 2 (Sfrp2). Recent studies in human patients have provided evidence that lack of FZD4, a member of the Wnt-signaling pathway, impairs normal retinal vascularization. BHLHB2 is a basic helix-loop-helix (bHLH) transcription factor and has been suggested to be involved in the control of proliferation and/or differentiation of several cells including nerve cells, fibroblasts and chondrocytes. Clusterins are molecular chaperones that prevent the amorphous aggregation and precipitation of target proteins under stress conditions and may be involved in Alzheimer's, Creutzfeldt-Jakob and Parkinson's diseases. Sfrp2 has been reported to