The RNAscope fluorescent in situ hybridisation, which allows specific identification and quantification of single transcripts28, showed a marked reduction in the endothelial KLF2 mRNA and increased expression of Notch4 and ETS-1 mRNA in the remodelled vasculature of IPAH patients, compared with healthy lungs (n = 6 per group) (Fig. 7a–e). The gene discussed is NOTCH4; the disease is idiopathic pulmonary arterial hypertension.