Figure 7

Preferential expression of the maternal allele of Tnfrh1 in fetal liver from CAST × BL/6 reciprocal crosses. A, Analysis of the MboII RFLP, in which the BL/6 allele is undigested and the CAST allele yields two fragments. There is a strong maternal allele bias in placenta, and a weaker but still obvious parent-of-origin dependent biases in fetal liver. This imprinting effect is superimposed on a non-imprinted bias for higher expression of the BL/6 allele. The allelic bias in placenta reflects expression from maternal cells, but the bias in fetal liver reflects parental imprinting. Similar results were obtained with multiple aliquots of cDNA (not shown). B=BL/6, C=CAST. (Note that only the internal comparisons of alleles in single PCR reactions are valid; the stronger band obtained from the CAST maternal kidney should not be compared to that from the BL/6 maternal kidney for intensity of expression, since these were separate RT-PCR reactions). B, Direct sequencing of RT-PCR products. This shows an allelic expression bias that depends on the direction of the cross, consistent with the RFLP results.