Isolated Ter119-positive fetal liver cells from three to five E14.5 embryos of the same genotype were combined, and total RNA was extracted using TRIzol reagent (Life Technologies) with two additional ethanol precipitations.  Microarray analyses were performed using Affymetrix Mouse Genome 430 2.0 array GeneChips (Affymetrix). Up- and down-regulated genes were selected based on P values of <0.05 and fold changes of >1.5 or -1.5 as assessed by ANOVA using Partek Pro software (Partek). To determine specific pathways, gene pathway analysis was obtained using the statistically significant gene list (P<0.05) represented on the chip.