Disruption of Vegfr1 in the endocardium results in the precocious and abnormal coronary plexuses.

A–H, Wholemount Pecam1 immunostainings of E11.5 hearts show the newly formed coronary plexuses in the ventricles. Note greatly increased formation of these primitive vessels by the R1 CKO hearts (B, D, F, H) compared to the control hearts (A, C, E, G). I, Statistic analysis showing the increase is significant. n = 7 hearts for each group, *pJ–O, Immunostained frontal sections of E11.5 ventricles with Pecam1 antibodies showing that the precocious coronary plexuses (red staining) in the R1 CKO ventricles are dilated and resemble the primitive blood islands (K, M, O; indicated by arrowheads and asterisks), which are not present in the control hearts (J, L, N). Dash lines and schematic diagrams showing these early-formed abnormal coronary plexuses within the myocardium of the R1 CKO hearts. ep, epicardium; myo, myocardium; oft, outflow track; lv/rv, left/right ventricle; tb, trabeculae; scale bar = 50 µm.