Glycogen synthase kinase-3 regulates DNA methylation near genes implicated in bipolar disorder

Colleen Marie Bartman, The College of Wooster

Abstract

Glycogen synthase kinase-3 (Gsk-3) functions as a regulator in many important cellular processes such as embryonic stem cell differentiation (Doble et. al., 2007), neural progenitor differentiation (Kim et. al., 2009), Wnt signaling (Doble et. al., 2007), and insulin signaling via phosphatidylinositol 3-kinase (PI3K) (Kockeritz et. al., 2006). Thus, altered Gsk-3 activity may contribute to diseases such as diabetes, Alzheimer disease, schizophrenia, and bipolar disorder (BPD). However, the precise mechanism by which altered Gsk-3 activity impacts these diseases is unknown. Understanding the effects of Gsk-3 inhibition on DNA methylation may shed light on the etiology of BPD and lead to better diagnostic tools and drug targets. Recently, Gsk-3 activity has been correlated with altered DNA methylation (Popkie et. al., 2010). To explore this further, we investigated the effect of Gsk-3 inhibition on DNA methylation in human embryonic stem (ES) cells and human neural stem (NS) cells. We hypothesized that inhibition of Gsk-3 would result in a reduction of DNA methylation. Illumina Next-Generation Sequencing Technology (Illumina, Inc. San Diego) and subsequent bioinformatic tools were used to identify Gsk-3-dependent differentially methylated regions (DMRs) and associated protein-coding genes. Molecular cloning and capillary sequencing was used to validate the DMRs suggested by Illumina data. We found a statistically significant correlation between ES cell Gsk-3-dependent DMRs and genes implicated in BPD. Capillary sequencing verified the location of two out of the eight ES and NS cell Gsk-3-dependent DMRs selected for validation. The close proximity of the DMRs to protein-coding genes may imply transcriptional regulation of the genes implicated in BPD.