Testis-specific isoform of angiotensin-converting enzyme (tACE) as a candidate marker for bull fertility

Testis-Specific Isoform of Na+-K+ ATPase and Regulation of Bull Fertility

An advanced understanding of sperm function is relevant for evidence-based male fertility prediction and addressing male infertility. A standard breeding soundness evaluation (BSE) merely identifies gross abnormalities in bulls, whereas selection based on single nucleotide polymorphisms and genomic estimated breeding values overlooks sub-microscopic differences in sperm. Molecular tools are important for validating genomic selection and advancing knowledge on the regulation of male fertility at an interdisciplinary level. Therefore, research in this field is now focused on developing a combination of in vitro sperm function tests and identifying biomarkers such as sperm proteins with critical roles in fertility. The Na+-K+ ATPase is a ubiquitous transmembrane protein and its α4 isoform (ATP1A4) is exclusively expressed in germ cells and sperm. Furthermore, ATP1A4 is essential for male fertility, as it interacts with signaling molecules in both raft and non-raft fractions of the sperm plasma membrane to regulate capacitation-associated signaling, hyperactivation, sperm-oocyte interactions, and activation. Interestingly, ATP1A4 activity and expression increase during capacitation, challenging the widely accepted dogma of sperm translational quiescence. This review discusses the literature on the role of ATP1A4 during capacitation and fertilization events and its prospective use in improving male fertility prediction.

Characterization of the Testis-Specific Angiotensin Converting Enzyme (tACE)-Interactome during Bovine Sperm Capacitation

A comprehensive understanding of molecular and biochemical changes during sperm capacitation is critical to the success of assisted reproductive technologies. We reported involvement of the testis-specific isoform of Angiotensin Converting Enzyme (tACE) in bovine sperm capacitation. The objective of this study was to characterize the tACE interactome in fresh and heparin-capacitated bovine sperm through immunoprecipitation coupled with mass spectrometry. These interactions were validated by co-localization of tACE with beta-tubulin as an identified interactome constituent. Although interactions between tACE and several proteins remained unchanged in fresh and capacitated sperm, mitochondrial aldehyde dehydrogenase 2 (ALDH2), inactive serine/threonine protein-kinase 3 (VRK3), tubulin-beta-4B chain (TUBB4B), and tubulin-alpha-8 chain (TUBA8) were recruited during capacitation, with implications for cytoskeletal and membrane reorganization, vesicle-mediated transport, GTP-binding, and redox regulation. A proposed tACE interactional network with identified interactome constituents was generated. Despite tACE function being integral to capacitation, the relevance of interactions with its binding partners during capacitation and subsequent events leading to fertilization remains to be elucidated.

Ligands and Receptors Involved in the Sperm-Zona Pellucida Interactions in Mammals

Sperm-zona pellucida (ZP) interaction, involving the binding of sperm surface ligands to complementary carbohydrates of ZP, is the first direct gamete contact event crucial for subsequent gamete fusion and successful fertilization in mammals. It is a complex process mediated by the coordinated engagement of multiple ZP receptors forming high-molecular-weight (HMW) protein complexes at the acrosomal region of the sperm surface. The present article aims to review the current understanding of sperm-ZP binding in the four most studied mammalian models, i.e., murine, porcine, bovine, and human, and summarizes the candidate ZP receptors with established ZP affinity, including their origins and the mechanisms of ZP binding. Further, it compares and contrasts the ZP structure and carbohydrate composition in the aforementioned model organisms. The comprehensive understanding of sperm-ZP interaction mechanisms is critical for the diagnosis of infertility and thus becomes an integral part of assisted reproductive therapies/technologies.

Characterisation of sperm piRNAs and their correlation with semen quality traits in swine

Piwi-interacting RNAs (piRNAs) are a class of non-coding RNAs that are essential in the transcriptional silencing of transposable elements and warrant genome stability in the mammalian germline. In this study, we have identified piRNAs in porcine sperm using male germline and zygote datasets from human, mice, cow and pig, and evaluated the relation between their abundances and sperm quality traits. In our analysis, we identified 283 382 piRNAs, 1355 of which correlated with P ≤ 0.01 to at least one semen quality trait. Fifty-seven percent of the correlated piRNAs mapped less than 50 kb apart from any other piRNA in the pig genome. Furthermore, piRNA location was significantly enriched near long interspersed nuclear elements. Moreover, some of the significant piRNAs mapped within or close to genes relevant for fertility or spermatogenesis such as CSNK1G2 and PSMF1.