Immunohistochemical Staining Protocol

Immunohistochemistry staining was performed as previously described^{10 (link)}. Briefly, paraffin-embedded sections were deparaffinized and rehydrated, followed by antigen retrieval as described in the ‘Immunofluorescence’ section. After the sections had cooled down to RT, they were penetrated with 0.4% Triton X-100 and incubated with 3% H₂O₂ for 20 min for the inactivation of endogenous peroxidase. The sections were then blocked with 5% donkey serum in PBS for 1 h and incubated with primary antibodies at 4 °C overnight. The sections were then incubated with horseradish peroxidase-conjugated secondary antibodies for 1 h at RT, followed by colorimetric detection using DAB and counterstaining with haematoxylin. Finally, the sections were dehydrated before being mounted in neutral resinous mounting medium. Images were captured using an Olympus VS200 system. The antibodies used are listed in Supplementary Table 8.