Gdnf−/− newborn (P0) mice display ∼80% renal agenesis and ∼20% severe renal hypodysplasia [1]–[3] (n = 28) (Figure 1A and 1B) (for statistical purposes, we count each of the two potential kidneys as a separate sample [22]). Here, GDNF is linked to renal agenesis.