Homozygous mice harbouring Noonan syndrome mutations for either Kras V14I (Hernández-Porras et al., 2014) or Sos1 E846K (Chen et al., 2010) mutation display pathological features similar to Noonan syndrome patients generally in homozygous background and pathologies strength develops in a gene dosage-dependent manner. Here, SOS1 is linked to Noonan syndrome.