Cluster 3 in both control and PAH were characterized by decreased expression of genes in cell-cycle and cell proliferation pathways, including cenpf, cdc25b, cenpw (centromere protein W), pclaf 9 (pcna clamp associated factor), and cdkn3 (cyclin dependent kinase inhibitor 3). The gene discussed is CDKN3; the disease is pulmonary arterial hypertension.