Induced DNA hypomethylation by Folic Acid Deprivation in Bovine Fibroblast Donor Cells Improves Reprogramming of Somatic Cell Nuclear Transfer Embryos.

ABSTRACT

Aberrant patterns of DNA methylation are consistent events in SCNT derived embryos and mechanistically are believed to be related to abnormal development. While some epigenetic drugs have been used in attempts to improve SCNT efficiency but some concerns remained toward the safety of these drugs on the health of future offspring. Folate is an essential cofactor in one-carbon cycle for conversion of homocysteine to methionine, thereby ensuring supply of SAM, the universal methyl donor for many biological methylation reactions including DNA methylation. Therefore, in vitro DNA hypo-methylation can be induced by folate deprivation and this study aims at deciphering the role of folic acid deprivation in culture medium of BFFs for 6 days on SCNT efficiency. Our data revealed that culture of fibroblast cells in folate- medium containing 0.5% FBS did not alter the cell cycle compared to other groups. Flowcytometric analysis revealed that DNA methylation (5-mC level) in folate deprived cells cultured in 0.5% serum was decreased compared to folate+ group. The result of bisulfite sequencing was in accordance with flowcytometric analysis, which indicated a decrease in DNA methylation of POU5F1 promoter. Gene expression analysis revealed an increase in expression of POU5F1 gene in folate- group. The nuclear area of the cells in folate- group was significantly larger than folate+ group. Induced DNA hypomethylation by folate deprivation in the folate- group significantly improved blastocyst rate compared to the folate+ group. DNA methylation level in POU5F1 promoter and ICR of H19 and IGF2 of SCNT derived embryos in the folate- group was similar to the IVF derived blastocysts. In conclusion, our results proposes a promising "non-chemical" instead of "chemical" approach using inhibitors of epigenetic modifier enzymes for improving mammalian SCNT efficiency for agricultural and biomedical purposes.