Relative comparison of the individual Genechip results. E18WT1 was used as a template for finding chips with a similar expression profile, using GeneSpring software. All samples were subjected to the correlation comparison. The result shows that the similarity of expression profiles to embryonic day (E)18 Nfia+/+ is as follows: postnatal day (P)16 Nfia+/+ < P16 Nfia-/- < E18 Nfia-/- < E18 Nfia+/+. The E18 Nfia+/+ expression profile exhibited greater correlation to the expression profile of P16 Nfia-/- than to that for P16 Nfia+/+. KO, knockout (Nfia-/-); WT, wild-type (Nfia+/+).