Human foregut morphogenesis exhibits murine-like molecular patterning but avian-like epithelial architecture

Animal models are indispensable for understanding human development, yet evolutionary relatedness does not ensure developmental similarity at all biological scales. In tracheal-esophageal separation (TES), which splits the embryonic foregut into respiratory and digestive tubes in all tetrapods, genetic mouse models rarely reproduce the predominant human malformation, esophageal atresia with tracheoesophageal fistula (EA/TEF). By comparing human, mouse, and chick foreguts, we uncover a mosaic pattern of developmental conservation. The human foregut resembles the mouse in its molecular patterning, but more closely resembles the chick in its densely pseudostratified epithelial architecture and the greater number of cells comprising the epithelial septum. Live imaging shows that epithelial pseudostratification, which depends on actomyosin contractility, is associated with slower septum resolution. Cross-species single-cell transcriptomics analysis reveals lower expression of a myosin regulatory light chain and N-cadherin, and higher expression of a myosin phosphatase subunit in the mouse foregut epithelium than in the human and chick, suggesting candidate molecular mechanisms of these morphological differences. Induction of ectopic BMP signaling through in vivo electroporation in chick embryos recapitulated an EA/TEF-like malformation. These findings suggest that human foregut morphogenesis combines murine-like patterning and avian-like epithelial organization. The chick embryo thus represents an important complementary model for investigating epithelial mechanisms underlying human foregut malformations.