Several proteins have been suggested as the causative circulating factors responsible for the occurrence of primary FSGS or recurrence of disease after kidney transplantation, including cardiotrophin-like cytokine-1 (CLC-1)11, vasodilator-stimulated phosphoprotein (VASP)12, anti-CD40 antibodies13 and soluble urokinase-type plasminogen activator receptor (suPAR)14. The gene discussed is VASP; the disease is focal segmental glomerulosclerosis.