SOX2 regulates foregut squamous epithelial homeostasis and is lost during Barrett's esophagus development.

Esophageal adenocarcinoma (EA) is increasingly prevalent and is thought to arise from Barrett's esophagus (BE), a metaplastic condition in which chronic acid and bile reflux transforms the esophageal squamous epithelium into a gastric-intestinal glandular mucosa. The molecular determinants driving this metaplasia are poorly understood. We developed a human BE organoid biobank that recapitulates BE's molecular heterogeneity. Bulk and single-cell transcriptomics, supported by patient tissue analysis, revealed that BE differentiation reflects a balance between SOX2 (foregut/esophageal) and CDX2 (hindgut/intestinal) transcription factors. Using squamous-specific inducible Sox2 knockout (Krt5CreER/+; Sox2∆/∆; ROSA26tdTomato/+) mice, we observed increased basal proliferation, reduced squamous differentiation, and expanded metaplastic glands at the squamocolumnar junction, some tracing back to Krt5-expressing cells. CUT&RUN analysis showed SOX2 bound and promoted differentiation-associated (e.g., Krt13) and repressed proliferation-associated (e.g., Mki67) targets. Thus, SOX2 is critical for foregut squamous epithelial differentiation and its decreased expression is likely an initiating step in progression to BE and thence to EA.