GATA3-extension mutants rewire lineage identity in luminal breast cancer

A new study reveals that a specific mutation in the GATA3 gene, known as eGATA3, can alter the identity of cells in luminal breast cancer. GATA3 is a crucial transcription factor that regulates the identity of luminal epithelial cells in breast cancer. While most mutations in GATA3 disrupt one of its zinc finger DNA-binding domains, eGATA3 retains both domains.

This suggests that eGATA3 may have unique effects on transcriptional regulation and cancer outcomes. To investigate this, researchers combined data from patient tumors, cell lines, and single-cell multiomics to analyze how eGATA3 impacts gene expression and chromatin structure. They discovered that eGATA3 is linked to worse patient outcomes and changes the way luminal genes are turned on and off.

Specifically, eGATA3 maintains its binding to DNA but shifts its focus to different types of regulatory elements. It loses binding at areas rich in AP-1 motifs and gains binding at FOX-associated enhancers. This redistribution of GATA3 binding coupled with changes in chromatin accessibility reshapes the regulatory landscape of luminal cells.

Crucially, these changes do not result in a complete change of cell identity but rather a reorganization that allows cells to maintain some luminal characteristics while losing others. The findings suggest that eGATA3 represents a distinct type of GATA3 mutation that promotes flexibility in cell fate decisions rather than a complete loss of identity.