Loss of imprinting at the Igf2r imprinted gene cluster in placenta in the absence of Smchd1 . ( A ) The Igf2r imprinted gene cluster shows imprinting in the placenta, where genes expressed from the paternal allele are shown in blue and those expressed from the maternal allele are in red. CpG islands are represented by circles on the line and where these represent an ICR (large circle) the methylation status is indicated (M inside the filled circle for the methylated allele or unfilled circle for the unmethylated allele). ( B ) In Smchd1+/+ F1 (C57Bl6/J sire × FVB/n dam) placental expression of both Igf2r and Slc22a3 is predominantly from the maternal FVB/n allele with only a minor proportion from the paternal C57Bl6/J allele, but in Smchd1MommeD1/MommeD1 placentas, expression of Slc22a3 becomes biallelic while expression of Igf2r remains imprinted with predominant expression of the maternal allele. ( C ) The same result is seen in the reciprocal cross F1 (FVB/n sire × C57Bl6/J dam) except here the maternal allele is derived from the C57Bl6/J dam. The genotype and number of replicates are indicated in each case. Statistical analysis was performed using the t test. ** P < 0.01 compared with wildtype. Error bars indicate standard error.