SOX2 is required for foregut squamous epithelial homeostasis and lost during Barrett’s esophagus development

Esophageal adenocarcinoma (EA) is increasingly common. EA is thought to arise from a precursor lesion, Barrett’s esophagus (BE), in which chronic bile and acid reflux from the stomach injures the esophagus and induces the esophageal squamous epithelium to transition to a mixed gastric and intestinal glandular mucosa. The molecular determinants driving this metaplasia are poorly understood. We established a biobank of human patient-derived BE organoids that recapitulated the molecular heterogeneity of BE. Bulk and single-cell transcriptomics, corroborated with analysis of patient tissues, pointed to BE differentiation depending on a balance between two transcription factors that govern foregut versus hindgut embryonic gastrointestinal development: SOX2 (driving esophageal and stomach differentiation) and CDX2 (driving intestinal differentiation). Using squamous-specific inducible Sox2 knockout (Krt5CreER/+; Sox2Δ/Δ;ROSA26LSLTdTomato/+) mice, we found increased basal proliferation and decreased differentiation in the foregut squamous epithelium. Remarkably, Sox2Δ/Δ mice also harbored expanded glands at the squamocolumnar junction, some of which lineage traced to Krt5-expressing cells, indicating metaplasia from squamous epithelium. 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 likely an initiating step in progression to BE and thence to EA.