DNA methylation profile of single in vitro matured bovine oocytes

Somatic cell nuclear transfer (SCNT) is commercially used despite incomplete nuclear reprogramming of the somatic cell nucleus by the enucleated oocyte compromising its efficiency. Oocyte selection is a key factor in increasing this efficiency as its cytoplasm reprograms the differentiated cell. In this study, we adapted a methodology to characterize epialleles in potential epigenetic markers in single in vitro matured oocytes. Characterization of the regions that control the expression of imprinted genes, X-chromosome inactivation, and satellite I DNA (IGF2, ICR-H19, XIST, RepA, and SAT1) showed methylated and unmethylated alleles in the imprinted genes IGF2 and ICR-H19 while XIST-DMR1 and RepA showed hypermethylated alleles. There was great variation in methylation patterns for candidate regions which may be related to oocyte quality. Moreover, the identification of different epialleles in the same oocyte suggests that, at least for those loci, the epigenome of the metaphase plate and polar body is different. The single-cell bisulfite polymerase chain reaction technique can be used to improve the precision of selecting the best oocytes for SCNT procedures, thereby increasing its efficiency.