IMPACT OF MALE FERTILITY STATUS ON THE TRANSCRIPTOME OF THE BOVINE EPIDIDYMIS

Study question: Can region-specific transcriptional profiling of the epididymis from fertile and sub-fertile bulls predict the aetiology of fertility/subfertility in males? Summary answer:The highly regulated gene expression along the bovine epididymis is affected by the fertility status of bulls used for artificial insemination. What is known already: In mammals, sperm maturation and storage occur in the epididymis. Each epididymal segment has his own transcriptomic signature that modulates the intraluminal composition that governs sequential modifications of the maturing male gamete. Main results and the role of chance: Hierarchical clustering and Principal Component Analysis revealed a clear separation between caput, corpus and cauda epididymides. Some transcripts characterize a particular anatomical segment, whereas others are expressed in two out of three epididymal segments. GO analysis allowed deduction of specific functions played by each epididymal segment. The transcriptional profiles between fertile vs. sub-fertile conditions clustered most closely in the corpus and cauda segments, whereas the profiles in the caput segment were distinct between fertile and sub-fertile bulls. Of the differently expressed genes, ten (including AKAP4, SMCP, SPATA3, TCP11, ODF1, CTCFL, SPATA18, ADAM28, SORD and FAM161A) were found to exert functions related to reproductive systems and 5 genes (including DEAD, CYST11, DEFB119, DEFB124 and MX1) were found to be associated with the defence response. Limitations, reasons for caution: Further work is required to correlate these modulations of epididymal functions with sperm fertilizing ability in order to understand the aetiology of certain cases of idiopathic infertility in livestock and men. Wider implications of the findings: As fertility can be quantified in bulls used for artificial insemination, this species is a unique model to aid in the understanding of male fertility/subfertility in man.Our data provide a molecular characterization that will facilitate advances in understanding the involvement of epididymalphysiology in sub/infertility aetiology.

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