PERM1 and persistent truncus arteriosus: At 4 weeks post-TAC, ejection fraction and fractional shortening were both significantly decreased in mluse hearts (Fig 2A, S1 Table), and the protein levels of the 100 kDa and 90 kDa Perm1 isoforms were decreased to 24.4 ± 5.9% and 10.3 ± 2.0%, respectively, compared to in the sham heart (Fig 2B and 2C).