According to Marsboom et al. [33], HIF-1 activation caused mitochondrial fission in human models of pulmonary arterial hypertension (PAH) by phosphorylation of DRP1 at serine 616 via cyclin B1/CDK1-dependent inhibition, whereas in normal pulmonary smooth muscle cells (PASMC), DRP1-mediated fission was caused by HIF-1 activation by cobalt chloride (CoCl2) or desferrioxamine. The gene discussed is CDK1; the disease is pulmonary arterial hypertension.