Validation of genes involved in the Wnt, Notch and BMP signaling pathways and early differentially expressed genes at PNW 1. (A) Twenty differentially expressed genes from the microarray were validated by RT-PCR using Gapdh as a reference gene. The time point that showed the greatest relative change in the microarray was selected for RT-PCR. (B) RNA was extracted from Pkd1L 3/L 3mice and age-matched control littermates at PNW 1. The RT-PCR and microarray results are compared in the same figure (mean ± SD of triplicate PCR reactions of pooled RNA; n = 3; *, P < 0.05; **, P < 0.01 compared with wild-type mice, by Student's t-test).