Extended Data Fig. 2: Assembloid generation.

a, Morphology of SRA formation when seeded at a density of 6000 organoids per mL over 10 days in floating collagen I hydrogel culture. Scale bars, 200 μm. b, Bright field images of MRA formation at Fundus, Body, and Antrum over 10 days in floating collagen I hydrogel culture. Scale bars, 200 μm. c, Bright field images of different parts of SRA at day 4 in culture: open section (upper panel), V-shaped fusion point marked by dotted yellow line (middle panel), tabularised section (lower panel). Scale bar, 200 μm. d, Bright field images of different parts of SRA at day 4 in culture showing syncytium formation. Scale bar, 200 μm. e, Immunofluorescence of sectioned gastric SRA showing mucin 6 (MUC6) in green, chromogranin A (CHGA) in red, F-actin (F-ACT) in cyan, and nuclei in blue (Hoechst); or mucin 5AC (MUC5AC) in green, integrin β4 (INT-β4) in red, and nuclei in blue (Hoechst). Scale bars, 50 μm. f, SRA section stained for Nuclei in white (RedDot), and Mucin 5AC (MUC5AC) in magenta (scale bar 50 μm).