MAPK3 and Noonan syndrome: While mice heterozygous for the Ptpn11Y279C allele readily recapitulated several hallmark features of Noonan syndrome, including cardiomyocyte hypertrophy, disarray, and fibrosis, in contrast to mice carrying the Raf1L613V allele, ERK1/2 activation was in fact attenuated in Ptpn11Y279C/+ heart tissues both at the basal state and in response to agonist stimulation [43].