Comparative analysis of piRNA profiles reveals cryoinjury or freezability between boar (Sus scrofa) and giant panda (Ailuropoda melanoleuca) sperm during cryopreservation

In this study, differentially expressed (DE)piRNAs of fresh and frozen-thawed sperm with different freeze tolerance compacity from giant panda and boar were evaluated. The results showed 1160 (22 down-regulated and 1138 up-regulated) and 384 (110 up-regulated and 274 down-regulated) differentially expressed (DE) piRNAs were identified in giant panda and boar sperm, respectively. Gene ontology (GO) enrichment analysis revealed that the target DE mRNAs of DE piRNAs were mainly enriched in biological regulation, cellular process and metabolic process in giant panda and boar sperm. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that the target DE mRNAs of DE piRNAs were only distributed on DNA replication and cAMP signaling pathway in giant panda, but cAMP, cGMP and MAPK signaling pathway in boar sperm which were considered as part of olfactory transduction pathway.Conclusion:Olfactory transduction related pathways maybe contributed to different freeze tolerance compacity between giant panda and boar sperm, which will benefit to further understand the molecular mechanism of sperm cryoinjury and freezability. Sperm piRNA profiles of fresh and frozen-thawed giant panda and boar sperm were generated by High-throughput sequencing.Giant pandas (n = 5) that were disease-free and exhibited normal fertility, sexual maturity and normal semen quality were selected from the Bifengxia base of China Conservation and Research. Boars (n = 11) that were disease-free and exhibited normal fertility, sexual maturity and normal semen quality were collected using an electro-ejaculation method