TCF7L2 Silencing Reprograms the 4D Nucleome of Colorectal Cancer Cells

Abstract

Canonical Wnt signaling is crucial for intestinal homeostasis as the major Wnt signaling effector in the intestines, TCF4, is required for stem cell maintenance. The capability of TCF4 to maintain the stem cell phenotype is contingent upon {beta}-catenin, a potent transcriptional activator which interacts with histone acetyltransferases and chromatin remodeling complexes. In colorectal cancer, mutations result in high levels of nuclear {beta}-catenin causing aberrant cell growth. Here, we used RNAi to explore the influence of TCF4 on chromatin structure (Hi-C) and gene expression (RNA sequencing) across a 72-hour time series in colorectal cancer. We found that TCF4 reduction results in a disproportionate upregulation of gene expression genome-wide, including a powerful induction of SOX2. Hi-C analysis revealed a general increase in chromatin compaction across the entire time series, though this did not influence gene expression. Analysis of local chromosome organization demonstrated a TAD boundary loss which influenced the expression of a cluster of CEACAM genes on chromosome 19. Four-dimensional nucleome (4DN) analysis, which integrates structural (Hi-C) and functional (RNA sequencing) data, identified EMT and E2F as the two most deregulated pathways and LUM, TMPO, and AURKA as highly influential genes in these networks. Results from gene expression, chromatin structure, and centrality analyses were then integrated to generate a list of candidate transcription factors for reprogramming of colorectal cancer cells to a vulnerable state. The top ranked transcription factor in our analysis was c-JUN, an oncoprotein known to interact with TCF4 and {beta}-catenin.