PDGFRA and Huntington disease: As validation, in a separate set of FFPE samples from PM brain of HD donors and controls (see methods), we combined fluorescent RNAScope in situ hybridisation probes (detailed in methods) for the shared upregulated HSP70 co-chaperone BAG3 with ITGAM, labelling microglia (Fig. 6A, B) or PDGFRA, labelling OPCs (Fig. 6C, D).