24108092

PMC3858462

DP1 GM105378/DP/NCCDPHP CDC HHS/United States
DP1 GM105378/GM/NIGMS NIH HHS/United States
F32 GM105189/GM/NIGMS NIH HHS/United States
F32 GM105189/GM/NIGMS NIH HHS/United States
P30 NS45776/NS/NINDS NIH HHS/United States
P50 HG005550/HG/NHGRI NIH HHS/United States
P50 HG005550/HG/NHGRI NIH HHS/United States
R01 CA169316/CA/NCI NIH HHS/United States
R01 CA169316/CA/NCI NIH HHS/United States
R01 HD045595/HD/NICHD NIH HHS/United States
R01 HD045595/HD/NICHD NIH HHS/United States
R01 HD053808/HD/NICHD NIH HHS/United States
R01 HD053808/HD/NICHD NIH HHS/United States
Howard Hughes Medical Institute/United States

CDC Public Access

Genome-wide studies have defined cell type-specific patterns of DNA methylation that are important for regulating gene expression in both normal development and disease. However, determining the functional significance of specific methylation events remains challenging, owing to the lack of methods for removing such modifications in a targeted manner. Here we describe an approach for efficient targeted demethylation of specific CpGs in human cells using fusions of engineered transcription activator-like effector (TALE) repeat arrays and the TET1 hydroxylase catalytic domain. Using these TALE-TET1 fusions, we demonstrate that modification of critical methylated promoter CpG positions can lead to substantial increases in the expression of endogenous human genes. Our results delineate a strategy for understanding the functional significance of specific CpG methylation marks in the context of endogenous gene loci and validate programmable DNA demethylation reagents with potential utility for research and therapeutic applications.