Because of the marked similarities in signal expression patterns between human IPAH and our PAH model animal prepared by S. chartarum, there were only 3 signal transduction pathways extracted that were uniquely affected in human IPAH PA in higher hierarchical pathways, namely, upregulation of the Wnt/PCP pathway and the succeeding Ras homolog gene family, member A/Rho-associated, coiled-coil–containing protein kinase (RhoA/ROCK) pathway, and down-regulation of the TGFβ pathway. The gene discussed is TGFB1; the disease is pulmonary arterial hypertension.