Biology subjects

Ghezzi, V.

Publications and source records attributed to Ghezzi, V..

2 recordsLinked to original sources

bioRxiv2023

The Developmental Transcription Factor TBX3 Physically Engages with the Wnt/β-catenin Transcriptional Complex in Human Colorectal Cancer Cells to Regulate Metastasis Genes

Wnt signaling orchestrates gene expression in a plethora of processes during development and adult cell homeostasis via the action of nuclear {beta}-catenin. Furthermore, neoplasia of the colorectal epithelium begins with aberrant Wnt/{beta}-catenin signaling. Yet, little is known about how {beta}-catenin generates context-specific transcriptional outcomes. We have previously identified the developmental transcription factor TBX3 as a tissue-specific component of the Wnt/{beta}-catenin nuclear complex during mouse forelimb development. In this study, we show that TBX3 is present and functionally active in human colorectal cancers. TBX3s genomic binding pattern suggests a regulatory role that broadly coincides with that of Wnt/{beta}-catenin. Moreover, proteomics proximity labelling indicated that, during Wnt pathway activation, TBX3 is vicinal to several protein partners, including the transcription factors TCF/LEF and chromatin remodeling complexes which are usually found at Wnt responsive elements. Sequence and structure analysis revealed that TBX3 possesses an exposed Asp-Pro-Phe (NPF) motif predicted by AlphaFold2 Multimer to mediate direct interactions with several Wnt-activated TBX3 partners. Deletion of NPF abrogates TBX3 proximity to these partners and its ability to modulate Wnt-dependent transcription. TBX3 emerges as a key modulator of the oncogenic activity of Wnt/{beta}-catenin in colorectal cancer, and its mechanism of action exposes a novel druggable protein-interaction surface.

developmental biology↗

bioRxiv2023

Single-cell response to Wnt activation in human embryonic stem cells reveals uncoupling of Wnt target gene expression

Wnt signaling drives nuclear translocation of {beta}-catenin and its subsequent association with the DNA-bound TCF/LEF transcription factors, which dictate target gene specificity by recognizing Wnt responsive elements across the genome. {beta}-catenin target genes are therefore thought to be collectively activated upon Wnt pathway stimulation. However, this appears in contrast with the non-overlapping patterns of Wnt target gene expression in several contexts, including early mammalian embryogenesis. Here we followed Wnt target gene expression in human embryonic stem cells after Wnt pathway stimulation at a single-cell resolution. Cells changed gene expression program over time consistent with three key developmental events: i) loss of pluripotency, ii) induction of Wnt target genes, and iii) mesoderm specification. Contrary to our expectation, not all cells displayed equal amplitude of Wnt target gene activation; rather, they distributed in a continuum from strong to weak responders when ranked based on the expression of the target AXIN2. Moreover, high AXIN2 did not always correspond to elevated expression of other Wnt targets, which were activated in different proportions in individual cells. This uncoupling of Wnt target gene expression, which was also identified in single colorectal cancer cells with hyper-activated Wnt signaling, underlines the necessity to identify additional mechanisms that explain the heterogeneity of the Wnt/{beta}-catenin-mediated transcriptional outputs in single cells.

developmental biology↗