In a rat model of PAH, the protein expression of IRE1α, p‐IRE1α, and XBP1s was significantly greater in the lung tissues of rats with PAH than in those without PAH,115, 116, 117, 118, 119 and knocking down XBP1s ameliorated PAH in rats.115, 116. The gene discussed is ERN1; the disease is pulmonary arterial hypertension.