Abnormal methylation of imprinted genes is commonly observed in the embryos cloned by somatic cell nuclear transfer (SCNT) procedure and is one of the primary reasons for their abnormal development and high mortality. Primordial germ cell 7 (PGC7), a developmentally regulated gene highly expressed in primordial germ cells, maintains the methylation level of imprinted genes by reducing the levels of 5-hydroxy-methylcytosine(5hmC) and increasing the levels of 5-methylcytosine(5 mC) during embryonic development. In this study, we explored the methylation status of H19 differentially methylated regions (DMRs) in the organs of SCNT-cloned goat fetuses. Our results showed abnormal methylation patterns of the imprinted genes in the lungs and placenta of dead cloned goat fetuses than those in normal goat fetuses. The Igf2r DMRs were hypomethylated in the heart, liver, spleen, lungs, kidneys, and placenta of dead cloned goat fetuses compared with normal goat fetuses (P < 0.05). In addition, imprinted gene Igf2r DMRs were hypomethylated in the early-stage SCNT embryos than the IVF embryos. In contrast, imprinted gene Xist DMRs were hypermethylated in SCNT embryos than the IVF embryos. Significantly, the use of PGC7 overexpressing donor cells corrected the abnormal methylation of imprinted genes Igf2r and Xist in SCNT embryos (P < 0.05). Our results suggested that PGC7 plays a vital role in maintaining the methylation of imprinted genes during goat early embryonic development. Moreover, PGC7 overexpression in donor cells may reduce the developmental abnormalities associated with the SCNT embryos, while significantly enhancing both the pregnancy and kids born rates (P < 0.05) thereby increasing SCNT efficiency in livestock.
Keywords: DNA methylation; Goat fetus; Imprinted genes; Primordial germ cell 7; Somatic cell nuclear transfer.
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