Molecular and DNA methylation analysis of Peg10 and Xist gene in sheep.

Peg10 is a maternally imprinted gene located in the imprinted domain of human chromosome 7q21 and mouse proximal chromosome 6. It is predominantly expressed in, and participates in the formation of, the placenta. Moreover, Peg10 is overexpressed in hepatocellular carcinoma, and is involved in hepatocarcinogenesis. The large noncoding RNA Xist has been shown to direct the female mammalian X chromatosome dosage compensation pathway. In the present study, we obtained partial cDNA sequences of sheep Peg10 and Xist. mRNA expression analysis in nine organs showed that they were universally expressed in two-day old lambs. The mRNA expression profile of Peg10 showed similar tissue specificity to pig, but was different compared with human and mouse. We concluded that the Peg10 mRNA expression profile was species specific. However, there was little difference in Xist expression between nine tissues of female lambs. Using bisulfite sequencing, we revealed that the first exon of Xist was either completely methylated or completely unmethylated, indicating that the newly obtained fragment of Xist was also differentially methylated in sheep as the DMR of Peg10. We did not find tissue specific DNA methylation of Xist, consistent with the Xist mRNA expression profile.