Fig. 2
From: Molecular causes of congenital anomalies of the kidney and urinary tract (CAKUT)
Illustration of ureteric budding, ureteric branching, initiation of nephron formation, and the extra cellular matrix (ECM) interface between UB and MM. a Ureteric budding from the nephric duct (“ND”) requires active GDNF/RET/GFRA1 signaling between the ureteric bud (“UB”) and the metanephric mesenchyme (“MM”). b Branching of the ureteric bud (“UB”) tip covered by cap mesenchyme (“CM,” yellow) containing nephron progenitor cells (“NPC”). c Subpopulations of NPC leave the cap mesenchyme niche, form peritubular aggregates (“PTA,” green), and undergo mesenchymal-epithelial transition to form renal vesicles (“RV,” orange) that will develop further into nephrons (not shown). d Illustration of the UB-cap mesenchyme (“CM”)-interface with the “Fraser Complex”-associated extra cellular matrix (ECM). FRAS1 and FREM2 (secreted from the UB) and FREM1 and nephronectin (expressed in the MM/CM) assemble in the extracellular space and bind to the Integrin a8/ß1 receptor located in cells derived from the MM