Figure 1. Early stages of renal vasculature development.

(a) Cellular compartments in the early metanephric kidney (modified from Sequeira-Lopez et al.⁵). (b) Provisional place of CD146⁺ precursors within the lineage hierarchy of the renal vasculature. Black arrows indicate current evidence, green arrow indicates a novel discovery by Holt et al.,⁷ dashed black arrows indicate lineage relationships that remain to be studied. Red dashed arrow indicates a suggested link that requires further experimentation. Specific factors characteristic of arterial, venous, capillary, and lymphatic ECs are not depicted for clarity. cadherin, calcium-dependent adhesion; CD, cluster of differentiation; c-Kit, tyrosine kinase receptor; EC, endothelial cell; Flk1, fetal liver kinase; Foxd1, Forkhead transcription factor; SCL, stem cell leukemia transcription factor; Six2, sine oculis-related homeobox gene 2; Tie1, tyrosine kinase with Ig-like and EGF-like domains 1; VE, vascular endothelial; UB, ureteric bud.