Extended Data Fig. 10: Schematic summary of the normal and metastatic leptomeningeal niche.

In the normal leptomeninges, meningeal fibroblasts are present and associate with meningeal blood vessels. In the presence of medulloblastoma (MB) metastatic tumour cells, secreted platelet-derived growth factor (PDGFA) ligands in the local microenvironment chemotactically recruit meningeal fibroblasts. Meningeal fibroblasts are reprogrammed to become MB-MAFs, expressing distinct transcriptomes and secretomes, including bone morphogenetic proteins 4 and 7 (BMP4/7). Active BMP and PDGF signalling further enhance both the colonization of the leptomeninges by MB cells as well as promoting the growth of established metastases.