Blood transcriptome of Rasa Aragonesa rams with different sexual behavior phenotype reveals CRYL1 and SORCS2 as genes associated with this trait

Reproductive fitness of rams is seasonal, showing the highest libido during short days coinciding with the ovarian cyclicity resumption in the ewe. However, the remarkable variation in sexual behavior between rams impair farm efficiency and profitability. Intending to identify in vivo sexual behavior biomarkers that may aid farmers to select active rams, transcriptome profiling of blood was carried out by analyzing samples from 6 sexually active (A) and 6 nonactive (NA) Rasa Aragonesa rams using RNA-Seq technique. A total of 14,078 genes were expressed in blood but only four genes were differentially expressed (FDR < 0.10) in the A vs. NA rams comparison. The genes, acrosin inhibitor 1 (ENSOARG00020023278) and SORCS2, were upregulated (log2FC > 1) in active rams, whereas the CRYL1 and immunoglobulin lambda-1 light chain isoform X47 (ENSOARG00020025518) genes were downregulated (log2FC < -1) in this same group. Gene set Enrichment Analysis (GSEA) identified 428 signaling pathways, predominantly related to biological processes. The lysosome pathway (GO:0005764) was the most enriched, and may affect fertility and sexual behavior, given the crucial role played by lysosomes in steroidogenesis, being the SORCS2 gene related to this signaling pathway. Furthermore, the enriched positive regulation of ERK1 and ERK2 cascade (GO:0070374) pathway is associated with reproductive phenotypes such as fertility via modulation of hypothalamic regulation and GnRH-mediated production of pituitary gonadotropins. Furthermore, external side of plasma membrane (GO:0009897), fibrillar center (GO:0001650), focal adhesion (GO:0005925), and lamellipodium (GO:0030027) pathways were also enriched, suggesting that some molecules of these pathways might also be involved in rams' sexual behavior. These results provide new clues for understanding the molecular regulation of sexual behavior in rams. Further investigations will be needed to confirm the functions of SORCS2 and CRYL1 in relation to sexual behavior.