Gene imprinting and X chromosome inactivation pattern in parthenogenetic embryonic stem cell.

Objective:To investigate the difference of X chromosome inactivation and imprinted gene expression status between the parthenogenetic human embryonic stem cells (phESC) and hESC derived from fertilized embryos. Methods: ①Relative quantitative real-time PCR was used to detect the paternally imprinted gene IGF2R and maternally imprinted gene SNRPN, IGF2 expression levels ② XIST methylation and histone H3 lysine 27 trimethylation (H3K27me3) were used to detected the X chromosome inactivation (XCI) status between the phESC and hESC. Results: ①maternally imprinted gene SNRPN, IGF2 were not expressed in phESC while the paternally imprinted gene IGF2R was expressed with more than 2 fold levels compared to the normal hESCs. ② No expression of XIST gene was detected at passage 35, which indicated that XCI was not initiated in phESC at early passages. After long-term culture, epigenetic status of these cells changed, XIST gene expression could be detected at passage 55 and the expression level was increased after differentiation. ③ DNA methylation status of promoter of XIST and positive H3K27me3 results also confirmed that phESC was initiated XCI. Conclusion:Variation XCI status suggested further investigation is necessary to clarify the epigenetic in phESC in order to ensure the safety of those cells for regenerative medicine.