Fig 2: Molecular characterization of arteriole and post-arterial capillary endothelial cells. Exclusive expression of the arterial marker GJA5 by BVs (white arrowheads (A)) and its overlay with HEY1 (B). The expression of ASS1 (C) and S100A4 (D) was restricted to the A and PAC clusters (white arrowheads). (E) Differential localization of ACKR1 and ASS1 discerns arterioles and post-arterial capillaries. Representative confocal images of section (upper) and whole-mount staining (lower) of ERG (green), ASS1 (red) and ACKR1 (white). Scale bars: 100 µm.

Fig 3: Endocardial-specific knockout of Ptbp1 leads to ventricular noncompaction.a Generation of the Ptbp1 endocardial-specific knockout (Nfatc1-Cre;Ptbp1fl/fl) mouse line. Top: schematic diagram showing the generation of the Nfatc1-Cre;Ptbp1fl/fl mouse line. Bottom: qRT-PCR examination of the Ptbp1 mRNA level in endothelial cells isolated from E13.5 Ptbp1fl/fl and Nfatc1-Cre;Ptbp1fl/fl hearts. n = 4 mice per group. b H&E staining showing the trabecular myocardium (TM) and compact myocardium (CM) in E13.5 Ptbp1fl/fl and Nfatc1-Cre;Ptbp1fl/fl heart tissue sections. Scale bars, 100 µm. c, d Representative images and quantification of the TM and CM thickness in E13.5 Ptbp1fl/fl and Nfatc1-Cre;Ptbp1fl/fl hearts. The graph shows the reduced thickness of the CM and increased thickness of the TM in Nfatc1-Cre;Ptbp1fl/fl hearts. n = 5 mice per group. The arrowheads indicate the expression of EMCN in the Nfatc1-Cre;Ptbp1fl/fl hearts. LV left ventricle, RV right ventricle. Scale bars, 100 µm. e Co-immunofluorescence staining of the endocardial cell marker EMCN and the trabecular myocardium marker CX40 in E13.5 Ptbp1fl/fl and Nfatc1-Cre;Ptbp1fl/fl heart sections. Scale bars, 100 µm. The asterisks indicate the expression of CX40 in the Ptbp1fl/fl hearts. The arrows indicate the reduced expression of CX40 in the Nfatc1-Cre;Ptbp1fl/fl hearts. f Immunofluorescence staining of the endomucin (EMCN) (green) in E13.5 Nfatc1-Cre;Ptbp1fl/fl and Ptbp1fl/fl heart sections. Scale bars, 200 µm. The graphs show quantification of the number of endocardial branch points, total area covered by the endocardial network, and total length of the endocardial network of E13.5 Nfatc1-Cre;Ptbp1fl/fl and Ptbp1fl/fl hearts. n = 3 mice per group. The data are presented as the mean ± s.e.m. P values were calculated by unpaired two-tailed t test. Source data are provided as a Source Data file.