Retinal vascular development in Mrp4-knockout mice. (A) Whole-mount immunostaining for PECAM in retinas from WT, Mrp4+/−, and Mrp4−/− mice at different postnatal stages. (B) Quantification of the vascular parameters at P3, P6, and P14. (C) Quantification of the vascular parameters at P6. N.S., not significant. The data are provided as the mean ± SD.