Aging of common carp (Cyprinus carpio L.) sperm induced by short-term storage does not alter global DNA methylation and specific histone modifications in offspring

Short-term storage of sperm is a useful tool to synchronize the availability of male and female gametes for fertilization in a hatchery. Induced aging by short-term storage has been shown to affect fish spermatozoa phenotypes including morphology and motility kinetics. However, its effects on epigenetics of sperm and the resulting embryos have not been investigated. In the present study, sperm of common carp (Cyprinus carpio) was stored in vivo and/or in vitro using an extender, and spermatozoa motility kinetics, viability, and epigenetics were analyzed. We observed that spermatozoa motility and velocity decreased following in vivo and/or in vitro storage from 3 to 6.5 days, but spermatozoa viability remained stable. At the same time, global DNA methylation, DNA hydroxymethylation, and specific histone acetylation and methylation were not affected by sperm aging. Further analysis showed no variation in global DNA methylation during embryogenesis when short-term stored sperm in the extender was used for fertilization compared with embryos produced from fresh sperm. The results suggest the reliability of short-term storage of sperm using an extender in fertilization and the production of the next generation of embryos. However, larval growth and performance need to be elucidated for these fish. This study has shed light on the potential application of extenders in storage of sperm in common carp breeding programs to manage selection, genomic manipulation and genetic resources conservation.