Transcription Factor–Guided Demethylation Defines Lineage and Cross-Lineage Epigenetic Regulation
** Lecture will be given in English**
Abstract:
Cell-type–specific DNA hypomethylation constitutes a fundamental epigenetic hallmark of cellular identity and plays a central role in regulating lineage-appropriate transcriptional programs. Recent studies indicate that transcription factors, particularly pioneer factors, are required for the establishment of these hypomethylated regions, with DNA demethylation enzymes such as TET proteins contributing to this process. However, the molecular mechanisms by which transcription factors selectively target genomic loci and recruit demethylation machinery remain incompletely understood. Elucidating these mechanisms is essential for defining how epigenetic landscapes are established and maintained during cell-fate specification .
To address this question, we investigated the pioneer factor FOXA2, a key regulator of endodermal differentiation, by generating a fusion protein linking FOXA2 to the catalytic domain of TET1 and ectopically expressing it in fibroblasts. Genome-wide DNA methylation profiling revealed an approximately 20% reduction in methylation levels at FOXA2 binding sites. Following withdrawal of FOXA2 expression, partial remethylation was observed; however, a subset of loci retained reduced methylation, consistent with the establishment of epigenetic memory. In addition to canonical FOXA2 targets, demethylation was detected at additional genomic regions, including sites corresponding to FOXA2 occupancy in alternative cellular lineages. Comparable patterns were observed upon expression of other transcription factors, including HNF1α and OCT4 .
These findings demonstrate that transcription factors can drive locus-specific and partially stable DNA demethylation at their binding sites, while also engaging lower-affinity sites across lineage contexts. This strategy provides a conceptual and technological framework for targeted epigenome editing to enhance lineage specification and differentiation protocols.
