Dynamics of cattle sperm sncRNAs during maturation, from testis to ejaculated sperm

Abstract

Background During epididymal transit, spermatozoa go through several functional maturation steps, resulting from interactions with epididymal secretomes specific to each region. In particular, the sperm membrane is under constant remodeling, with sequential attachment and shedding of various molecules provided by the epididymal lumen fluid and epididymosomes, which also deliver sncRNA cargo to sperm. As a result, the payload of sperm sncRNAs changes during the transit from the epididymis caput to the cauda. This work was designed to study the dynamics of cattle sperm sncRNAs from spermatogenesis to final maturation. Results Comprehensive catalogues of sperm sncRNAs were obtained from testicular parenchyma, epididymal caput, corpus and cauda, as well as ejaculated semen from three Holstein bulls. The primary cattle sncRNA sperm content is markedly remodeled as sperm mature along the epididymis. Expression of piRNAs, which are abundant in testis parenchyma, decreases dramatically at epididymis. Conversely, sperm progressively acquires miRNAs, rsRNAs, and tsRNAs along epididymis, with regional specificities. For instance, miRNAs and tsRNAs are enriched in epididymis cauda and ejaculated sperm, while rsRNA expression peaks at epididymis corpus. In addition, epididymis corpus contains mainly 20 nt long piRNAs, instead of 30 nt in all other locations. Beyond the bulk differences in abundance of sncRNAs classes, K-means clustering was performed to study their spatiotemporal expression profile, highlighting differences in specific sncRNAs and providing insights into their putative biological role at each maturation stage. For instance, Gene Ontology analyses using miRNA targets highlighted enriched processes such as cell cycle regulation, response to stress and ubiquitination processes in testicular parenchyma, protein metabolism in epididymal sperm, and embryonic morphogenesis in ejaculated sperm. Conclusions Our findings confirm that the sperm sncRNAome does not simply reflect a legacy of spermatogenesis. Instead, sperm sncRNA expression shows a remarkable level of plasticity resulting probably from the combination of multiple factors such as loss of the cytoplasmic droplet, interaction with epididymosomes, and more surprisingly, the putative in situ production and/or modification of sncRNAs by sperm. Given the suggested role of sncRNA in epigenetic trans-generational inheritance, our detailed spatiotemporal analysis may pave the way for a study of sperm sncRNAs role in embryo development.

Assessing spermatozoal small ribonucleic acids and their relationship to blastocyst development in idiopathic infertile males

“…However, only 5% of reads mapped to piRNAs. Other studies have also reported a minority of piRNAs in mature mammalian sperm, despite representing a considerable proportion in immature sperm in the testes and throughout spermatogenesis 15 . It has been proposed that dissociation of piRNA complexes that contribute to mRNA inactivation and remodeling in late spermiogenesis may render its associated piRNAs vulnerable to nuclease-mediated degradation 55 .…”

Investigation of Sperm and Seminal Plasma Candidate MicroRNAs of Bulls with Differing Fertility and In Silico Prediction of miRNA-mRNA Interaction Network of Reproductive Function

“…Sellem et al (2021) investigated the dynamics of bovine sperm small RNAs from spermatogenesis to final maturation and observed that sperm progressively acquires miRNAs during the epididymal transit with regional specificities [ 138 ]. Several miRNAs are involved in cell cycle regulation, spermatogenesis, or embryo development, suggesting the role of epididymal small RNAs in sperm maturation and for ejaculated sperm in embryogenesis.…”

The Dynamic of PRAMEY Isoforms in Testis and Epididymis Suggests Their Involvement in Spermatozoa Maturation

“…When the cytoplasm of elongated spermatids is shed at the end of spermiogenesis, the CB, and MAG, which contain PRAMEY, will also be lost from the spermatids through the cytoplasmic droplets. It is believed that the cytoplasmic droplets are released mainly in the caput segment of the epididymis during sperm transition from the testis to cauda epididymis in sperm maturation ( Branton and Salisbury, 1947 ; Cooper and Yeung, 2003 ; Zhou et al, 2018 ; Sellem et al, 2021 ). Therefore, PRAMEY may be shed into epididymal lumen fluid during maturational passage of spermatozoa.…”