Table 1 compares selected findings in these mice and in the other 4 strains of Kras knock-in mice reported to date (6, 9, 25, 29, 40, 47). KrasLSL-P34R/+ and KrasLSL-T58I/+ mice are valuable models for performing preclinical studies of MEK inhibitors and other potential therapies for reversing or preventing severe and life-threatening complications in patients with RASopathy. Indeed, 2 young children with severe hypertrophic cardiomyopathy were recently reported who improved after receiving a MEK inhibitor (48). The gene discussed is KRAS; the disease is hypertrophic cardiomyopathy.