The aim of this experiment was to use highthroughput chromatin immunoprecipitation followed by hybridization to promoter microarrays to obtain a comprehensive list of sites in the genome that are physically occupied by Pdx1. Chromatin was prepared from Min6 insulinoma cells and immunoprecipitated with Pdx1 or control antiserum. The precipitated chromatin was then purified, amplified and directly sequenced using Illumina technology.

Identify Pdx1 transcriptional targets involved in ER function as part of a larger study to define the role of Pdx1 in compensatory beta cell mass expansion that occurs in the progression to type 2 diabetes in humans.

Microarray expression results were integrated with the results of a ChIP-on-chip experiment of Pdx1 occupancy, also in Min6 cells using Mouse PromoterChip BCBC-5A.

The proximal promoters of ER target genes, Atf4 and Wfs1, were directly occupied by Pdx1. Two evolutionarily-conserved genomic sequences were found within 1.5 kb upstream of the Atf4 transcriptional start site, each of which contain at least one conserved Pdx1 consensus binding motif T(T/A)AT. ChIP assays demonstrated Pdx1 occupancy of both regions in Min6 cells. Occupancy of the Wfs1 promoter by Pdx1 was also confirmed both in Min6 cells and in primary mouse islets.

Pdx1 regulates a broad array of genes involved in diverse functions of the ER, including proper disulfide bond formation, protein folding, and the unfolded protein response. These findings suggest that Pdx1 deficiency leads to a failure of beta cell compensation for insulin resistance at least in part by impairing critical functions of the ER.

• Pdx1: 3975, 3977, 3979, 4474,
• stress and apoptosis in islets/ beta cells: 751, 2000, 2001, 2020, 2021, 2301, 2904, 3244, 3650, 3975, 3977, 3979, 3980,