Circular RNAs as biomarkers for porcine sperm motility

Resumen del póster presentado a la 37th International Conference on Animal Genetics (ISAG), celebrada en Lleida (España) del 7 al 12 de julio de 2019.
Male fertility in swine has been associated with sperm motility parameters. Sperm movement is regularly assessed in Artificial Insemination studs and provides an objective and reproducible measurement of semen quality. As sperm transcripts are highly fragmented and present at low abundances we seek to investigate circular RNAs (circRNAs), a novel class of non-coding RNAs with a closed loop structure, more stable than linear transcripts and potentially acting as miRNA sponges. We have performed total and small RNA-seq from 40 boar sperm samples. The objective of this study was to characterize the porcine circRNA repertoire, assess their potential role as miRNA sponges and the correlation between their abundance and sperm motility. We identified 1,393 potential circRNAs across all the 40 samples. The majority of the circRNAs were derived from exonic regions (63.6%), formed from less than 4 exons and had an average lenght below 500 bp. circRNA abundances ranged between 0.18 and 137 CPMs. Compared with other pig tissues, the sperm circRNA repertoire resembled most to testis, even thought 75% of the sperm circRNAs were sperm-specific. Gene ontology analysis revealed that sperm circRNAs involved genes related to epigenetic regulation, spermatogenesis and cilium assembly functions. We identified 69 circRNA-miRNA interactions. For example, miR-28–5p, a miRNA that is dysregulated in human infertile patients, presented 2 different target sites in a circRNA from ZMYND10, a gene required for motile ciliary function. We identified 148 circRNAs that correlated with different sperm motility parameters. We selected 10 circRNAs and validated the closed loop structure by RT-qPCR and Sanger Sequencing. The RNA abundance of 6 cirRNAs was validated by RT-qPCR and compared in 38 additional animals presenting extreme motility parameters. Three circRNAs presented significant differences in abundance between the groups. These included circRNA from LIN7A (P-value: 0.008), LRBA (P-value: 0.04) and PAPOLA (P-value: 0.026) genes, the functions of these genes are related to generating and maintaining cell membrane channels, vesicle trafficking and RNA and ATP binding, respectively.