COL4A4 and persistent truncus arteriosus: At the 3-week timepoint we identified structural changes in TAC mice treated with 29P; however, 6-weeks post-TAC, there was no difference to percentage fibrosis in the left ventricle, TWOMBLI-assessed number of fibrosis branchpoints (Supplementary Fig. 5A and B) or Col4a3 and Col4a4 transcripts between Veh- and 29P-treated TAC mice (Supplementary Fig. 5C).