Methylated DNA Immunoprecipitation (meDIP) was used to pull down regions of methylated genomic DNA from beta and alpha cell lines (MIN6 and alpha-TC1, respectively). Agilent promoter tiling array was used to look for regions of differential methylation around key endocrine cell fate determination genes.

Test hypothesis that key determinants of the alpha cell lineage were methylated and repressed to maintain beta cell lineage stability, and these determinants were derepressed in the beta cells deficient in DNA methylation

To identify methylated alpha cell lineage determinants, genome-wide mapping of DNA methylation patterns at 5' upstream promoter regions was carried out using the methylated DNA immunoprecipitation (MeDIP) method. Methylated CpG-enriched DNA fractions using anti-5-methyl cytosine antibody (Aviva Systems Biology AMM99021) were collected from mouse alpha and beta cell lines (alpha-TC1 and Min6) and hybridized to the Agilent Mouse Promoter Whole Genome ChIP-on chip Set 244K: 014716 and 014717. Screening was done of 5' upstream regulatory regions that showed higher methylation levels in Min6 cells when compared with a-TC1 cells.

Analysis of the methylation profiles of endocrine cell fate determination genes led to the identification of two CpG-rich regions in the 5' regulatory region of Arx that were differentially methylated in Min6 and a-TC1 cells.

Methylation of Arx regulatory regions in beta cells may correlate to its repression in beta cells.

• islet epigenomics: 3918, 4075, 4078, 4114, 4175, 4235, 4395, 4514,