Extended Data Figure 8. Screen for pathways that promote differentiation of parietal cells in fundic hGOs.

a, To test for growth factors/small molecules capable of inducing parietal cell differentiation, hFGOs were exposed for two days (30–32) to the indicated agonist or antagonist and then analyzed at day 34. In a screening experiment of different pathways, only MEK inhibition with PD03 was found to robustly induce expression of ATP4A/B. b, Reduction or removal of EGF from the culture medium was not sufficient to reproduce the effect of MEK inhibition. c, The ability of PD03/BMP4 to induce parietal cell development was exclusive to fundic hGOs, as antral hGOs did not express fundic markers in response to PD03/BMP4. d, Exposure to PD03/BMP4 rapidly increased expression of ATP4A and ATP4B in fundic hGOs. e, Induction of parietal cell generation with PD03/BMP4 did not significantly impact the differentiation of chief cells (PGA5 and PGC) and endocrine cells (CHGA). f, The manipulations at each stage of the hFGO differentiation protocol was required for robust parietal cell differentiation, as removal of any single step led to loss of ATP4A/B expression. Error bars represent s.d. (a–c) and s.e.m. (d–f).