(A) Relative enrichment analysis of 5fCpG sites located in repeat elements and the subfamilies. (B) The line chart showing the 5fCpG level on subfamilies of repeat elements throughout the human early embryo developmental stages. The center is the mean of 5fCpG level and error bars are SEM. (A–B) The sample size in these panels are listed in Fig 1A, and the numerical data are listed in S1 Data. (C–D) The UCSC browser view of 5fCpG sites located in L1 (C) and ERVK (D). CGI, CpG island; ERVK, endogenous retrovirus-K; ERVL-MaLR, endogenous retrovirus-L, mammalian-apparent long-terminal repeat retrotransposon; hESC, human embryonic stem cell; ICM, inner cell mass; MIR, mammalian-wide interspersed repeat; PB, polar body; SEM, standard error of the mean; TE, trophectoderm; UCSC, University of California, Santa Cruz; 5fCpG, 5-formylcytosine phosphate guanine.