This suggests that one of the following is true: (a) the mutations do not result in nonsense-mediate mRNA decay, but are not translated; (b) the mutations do not result in nonsense-mediate mRNA decay, are translated, but produce non-functional proteins; or (c) there is neomorph function to MAP3K1 mutations in breast cancer that our studies do not recapitulate, which would require more in-depth knock-in mutation studies. This evidence concerns the gene MAP3K1 and breast cancer.