Abstract
TET1-mediated active DNA demethylation is required for endogenous retrovirus (ERV) enhancer activation during human ES differentiation into definitive endoderm (DE) cells. Here we present a protocol for siRNA-mediated TET1 knockdown during this process to decipher TET1's role in ERV activation and DE differentiation. We describe steps for inducing ES into DE cells. We then detail steps for knocking down TET1 during differentiation and for examining the effects of TET1 knockdown on LTR6B methylation, cell morphology, and gene expression. For complete details on the use and execution of this protocol, please refer to Wu et al. (2022).1.