Fig. 2. Allele-specific expression in ES and TS cells. RT-PCR was used to analyse the allele-specific expression of genes within the Kcnq1 domain in undifferentiated C57BL/6J (B6)xM.m. castaneus (Ca) ES and TS cells. Maternal (M) and paternal (P) alleles were distinguished using RFLP or deletion/insertion polymorphisms described in the Materials and methods. The non-coding RNA Kcnq1ot1 is labelled in black, ubiquitously imprinted genes are labelled in green and placental specific imprinted genes are labelled in purple. For each gene, a representative sample is shown with its corresponding reverse transcriptase-negative control. Phlda2, Cdkn1c and Kcnq1ot1 exhibit monoallelic expression, and Tssc4 and Osbpl5 show biallelic expression in both cell types. Cd81 shows expression from both alleles although there is a bias towards the maternal allele. We corrected for primer bias by densitometry and normalisation to a mix of 50% B6 cDNA and 50% Cast cDNA. The parental ratio of Cd81 in ES cells is 1:1, whereas TS cells show a ratio of 3.5:1.