In contrast to whole blood cDNA, when we used an equivalent amount of cDNA from ARPKD URECs, we were able to obtain amplification of the target region of PKHD1 by RT-PCR, indicating that the low expression levels of PKHD1 in the blood (Table 2) may render the amplification by RT-PCR of the corresponding cDNA inefficient (Additional Figure 1). Here, PKHD1 is linked to autosomal recessive polycystic kidney disease.