(A–I) Hematoxylin and eosin-stained sections of P0 kidneys from control (A–C), heterozygous (D–F) and Six2PRR−/− (G–I) mice demonstrate reduced kidney size, lack of well-defined nephrogenic zone, thin cortex with apparent reduction in nephron number, presence of cysts (Cy) in the cortex and medulla in Six2PRR−/− mutants. (A,D,G) scale bar= 100 µm; numbers- kidney length. (J,K) Bar graphs demonstrate a decrease in total nephron number (J) and in number of all nephron generation stages (K) Six2PRR−/− mutants compared to controls.