Fig. 1: Morphological and molecular comparison of chick and mouse tracheal-esophageal separation (TES), a model system for studying epithelial splitting.

a Schematic of TES. The airway (purple) and the esophagus (green) form through foregut splitting. The inset shows the cross-section of the foregut at the level of TES along the dashed line. The inset was created in BioRender. Yan, R. (2025) https://BioRender.com/cdwttt9. b Whole mount immunofluorescence of E-cadherin (CDH1) of chick and mouse foreguts during TES. Images show lateral views from the right. The red and blue line segments indicate the lengths of the undivided foregut and the trachea. c Quantification of the lengths of the undivided foregut (red) and the trachea (blue) during TES from whole mount images. N = 4 biological replicates for each stage. Data are presented as mean ± standard deviation (SD). d Immunofluorescence of SOX2 and NKX2-1 in transverse sections of the chick and mouse foreguts during TES. e Quantification of SOX2 intensity along the dorsal-ventral axis (N = 6 biological replicates). Data are presented as mean ± SD. f, g Immunofluorescence of cleaved Caspase 3 (CC3) (f) and phospho-Histone H3 (pHH3) (g) in transverse sections of chick and mouse TES. Arrows point to the tracheal-esophageal septum. h Immunofluorescence of phospho-MLC2 (pMLC) in serial transverse sections of chick and mouse foreguts, from the anterior undivided foregut through the posterior separated foregut. i Quantification of the apical-basal ratio of pMLC intensity in the dorsal, medial, and ventral foregut epithelium (N = 7 biological replicates for each species). Data are presented as mean ± SD. Scale bars: 100 µm (b), 50 µm (d, f–h). Double arrows indicate the dorsal-ventral axes for tilted samples.