Epigenetics in fish gametes and early embryo

The spermatozoa and oocyte are very specialized cells which possess the unique ability to fuse and to produce an embryo. This embryo will develop into a mature organism capable of producing gametes again. This colloquial statement comprehends however the most complex mechanisms in biology, namely, cell differentiation and cell reprogramming. Epigenetic modifications are major actors in this process, both during gametogenesis and embryo development. The epigenetic concept is resulting from the growing scientific understanding of embryology and genetics, and it is made operational by generic molecular mechanisms, namely DNA methylation, histone tails modifications, and non-coding RNAs. Epigenetic modifications associated with gamete differentiation and early embryo development are quite well described in mammals, but increasing research is developed in fish today, either in model or in aquaculture species. Because fish are living organisms thoroughly exposed to temperature and to water quality, environment is likely to influence the epigenetic pattern of the gametes, embryo, or adult organisms. Reproductive biotechnologies are also at risk to modify gametes and embryo epigenetics. This review is aimed towards giving the basic knowledge on the molecular actors of epigenetics, highlighting the developing knowledge in mammals which can be useful to fish research and proposing the possible area where epigenetics can enrich research on fish gametes and reproductive technologies.