Analysis of the Boar Sperm Transcriptome Reveals RNAs Related to Spermatogenesis and Highlights Transcripts Related to Sperm’s Loss of Viability

Insemination boars are selected based on their genetic merit for production traits. As a consequence, a proportion of these boars end up being rejected due to poor semen quality. Thus, an early prediction test of semen quality would help selecting better boars thereby improving the efficiency of insemination centers. Mature sperm contains a small population of highly degraded RNAs which might be related to semen quality and fertility. The objective of our study was to profile the boar’s sperm transcriptome and identify the transcripts that are linked to the loss of spermatozoa viability (LSV) after incubation at 37ºC. Ejaculated sperm from 6 pigs with either good (n=3) or bad (n=3) LSV was subjected to RNA-seq. We then applied two computational workflows: (1) GEM+edgeR and (2) TopHat+Cufflinks and selected the 10,235 transcripts that were identified by both workflows. The 10% most highly expressed genes accounted for 98.8% of the transcript abundance. These were mostly related to spermatogenesis, ribosome assembly and translation. Differential expression analysis comparing the good and bad LSV samples highlighted 96 under- and 10 over-expressed genes (FDR < 0.05) in the good LSV spermatozoa. Some of these genes are related to male infertility and abnormal spermatogenesis according to the Mouse Genome Informatics database. In keeping with studies on other mammals, our results suggests a high specialization of the boar’s sperm transcriptome in which most abundant RNAs are related to spermatogenesis and fertility and relates some transcripts to LSV.