RAF1 and Noonan syndrome: In Noonan syndrome, gain-of-function mutations in PTPN11 (12q24.13), NRAS (1p13.2), SOS1 (2p22.1), RAF1 (3p25.2), BRAF (7q34), KRAS (12p12.1), and MAP2K1 (15q22.31) genes may activate the Ras-Raf-MEK-ERK signaling pathway (20, 81–84).