Translating human PPARy binding regions to gene regulation and metabolic disease

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DESCRIPTION (provided by applicant): This application is for Dr. Raymond Soccio to develop his career as an academic physician-scientist focusing on the molecular mechanisms of obesity and type 2 diabetes. The career development plan includes training in genomics, bioinformatics, and computational biology, since a thorough understanding of these burgeoning fields will be essential to the cutting-edge studies proposed. There will be formal mentoring by the sponsor Dr. Mitchell Lazar and a multi-disciplinary mentorship committee of distinguished scientists. The University of Pennsylvania offers a remarkably rich environment, with access to collaborators, educational resources, and facilities that will foster Dr. Soccio's professional development. Research will focus on PPAR , a nuclear receptor transcription factor and the master regulator of fat cell development. PPAR is a target for anti-diabetic drugs and a gene associated with type 2 diabetes in genome-wide association studies (GWAS). Our initial studies used chromatin immunoprecipitation and massively parallel sequencing (ChIP-Seq) to identify the genome-wide binding sites, or cistrome, for PPAR in cultured human adipocytes. We found tens of thousands of binding sites, showing the power of cistromics to yield enormous amounts of unforeseen data, yet only ~10% were retained at corresponding locations in the mouse genome, highlighting the importance of translational investigation of human cells and tissues. Specific Aim 1 is to determine function of the PPAR cistrome, by integrating the binding sites with regulated gene expression and markers of active chromatin. We hypothesize that this may reveal general rules for regulated gene transcription by PPAR. Specific Aim 2 is to determine the PPAR cistrome in human adipose tissue, rather than in cultured adipocytes. We hypothesize that this will reveal additional relevant sites and allow clinically important comparisons. Specifi Aim 3 is to translate the PPAR cistrome to the genetics of human metabolic disease. GWAS indentify single nucleotide polymorphisms (SNPs) associated with disease, but only rarely does the SNP affect protein coding sequence, thus most are believed to affect gene regulatory regions. Since PPAR is linked to diabetes, we hypothesize that variants in PPAR binding sites affecting its target genes could likewise lead to metabolic disease. SNPs will be identified in PPAR sites where one allele has better predicted binding, then interrogated in the imputed datasets for large metabolic GWAS. Thus, cistromics could powerfully complement genetics by revealing novel associations not found in the initial GWAS and by providing the missing mechanistic link between genotype and phenotype. We will assay allelic imbalance in PPAR binding as a first step linking SNP to disease. Given the scope of the datasets, novel genes and pathways will inevitably be discovered in Aims 2 and 3, and further investigation of these will transition Dr. Soccio from the mentored to the independent phase of this 5 year career development award. These studies of the human PPAR cistrome have potentially great translational relevance to the epidemics of diabetes and obesity. . PUBLIC HEALTH RELEVANCE: This proposal focuses on PPAR, which binds DNA to regulate genes important for fat cell metabolism. We have identified tens of thousands of binding sites for PPAR in the human genome, and propose powerful translational studies connecting these to human genetics. Since PPAR is strongly linked to obesity and type 2 diabetes, we hypothesize that its binding sites may reveal novel regulatory mechanisms - and thus new diagnostic and therapeutic targets - in these epidemic diseases.