5-methylcytosine is a major epigenetic modification
that is sometimes called ‘‘the fifth nucleotide.’’ However,
our knowledge of how offspring inherit the DNA
methylome from parents is limited. We generated
nine single-base resolution DNA methylomes,
including zebrafish gametes and early embryos.
The oocyte methylome is significantly hypomethylated
compared to sperm. Strikingly, the paternal
DNA methylation pattern is maintained throughout
early embryogenesis. The maternal DNA methylation
pattern is maintained until the 16-cell stage. Then,
the oocyte methylome is gradually discarded
through cell division and is progressively reprogrammed
to a pattern similar to that of the sperm
methylome. The passive demethylation rate and the
de novo methylation rate are similar in the maternal
DNA. By the midblastula stage, the embryo’s methylome
is virtually identical to the sperm methylome.
Moreover, inheritance of the sperm methylome
facilitates the epigenetic regulation of embryogenesis.
Therefore, besides DNA sequences, sperm
DNA methylome is also inherited in zebrafish early
embryos.