TP53 and cardiac hypertrophy: By contrast, all the Mdm4+/T454M p53+/Δ31 compound heterozygotes died in less than 3 months and exhibited intense skin hyperpigmentation, short stature, cardiac hypertrophy, testicular hypoplasia, bone marrow failure, and short telomeres, again indicating that the Mdm4T454M mutant is extremely sensitive to variations in p53 signaling [41].