Transfection of non-PAH sPASMCs constitutively expressing NOTCH3 ICD with HES5-specific small interfering RNA (HES5 siRNA) resulted in significantly decreased HES-5 expression, with reduced 3[H]leucine incorporation and cellular proliferation compared to non-PAH sPASMCs transfected with a control (scrambled) oligonucleotide [8]. The gene discussed is NOTCH3; the disease is pulmonary arterial hypertension.