MERTK and neoplasm: In sections of SMG organoids, we observed the expression patterns of alpha smooth muscle actin (α-SMA), Na–K-Cl cotransporter-1 (NKCC1), cytokeratin 18 (CK18) and aquaporin 5 (AQP5)23–26, and in the sections of human brain tumor biopsies, we assayed for the tumor-specific markers epidermal growth factor receptor (EGFR), c-Mer proto oncogene tyrosine kinase, and oligodendrocyte transcription factor 2 (Olig2)27,28.