STYXL1 regulates CCT complex assembly and flagellar tubulin folding in sperm formation

The effect of cryopreservation on the turkey (Meleagris gallopavo) semen proteome

Two-dimensional difference in-gel electrophoresis coupled with matrix-assisted laser desorption/ionization mass spectrometry was employed to investigate the proteome alterations induced by equilibration and freezing/thawing processes, both in turkey spermatozoa and in extracellular fluid (ECF). The freezing/thawing process resulted in reduced semen quality parameters. Viability and motility decreased threefold (90.6 %-31.2 % and 76.0 %-26.7 %, respectively), while the proportion of live spermatozoa with intact mitochondrial membrane potential decreased fivefold (54.9 %-11.4 %). Additionally, oxidative stress increased sevenfold (10.5 %-68.8 %). A total of 146 differentially abundant protein spots were found between fresh and frozen/thawed spermatozoa, while 27 spots differentiated between fresh and frozen/thawed ECF. Immunofluorescence staining showed reduced signals of mitochondrial proteins, such as aconitate hydratase, alpha-enolase, glycerol-3-phosphate dehydrogenase, and triosephosphate isomerase, in the spermatozoa midpiece, as well as reduced signals of acrosin in the acrosome. Freezing/thawing affected mitochondrial energy metabolism, particularly the tricarboxylic acid (TCA) cycle and oxidative phosphorylation. The maintenance of an acetyl-CoA pool to sustain TCA cycle activity in cryopreserved spermatozoa may be insufficient owing to disturbances in fatty acid beta-oxidation and/or aerobic glycolysis. Changes in the ECF primarily reflect the leakage of spermatozoa glycolytic enzymes. The freezing/thawing process alters motile cilium assembly, primarily affecting the spermatozoa axoneme and outer dense fibres. The initial step of fertilization may be disrupted by alterations in proteins involved in spermatozoa binding to the ovum. These findings extend our knowledge of the molecular and cellular mechanisms of cryodamage in turkey semen which is prerequisite for the improvement of semen preservation procedures.

UBL7 is indispensable for spermiogenesis through protecting critical factors from excessive degradation by proteasomes

Spermiogenesis is a tightly regulated process to produce mature sperm cells. The ubiquitin-proteasome system (UPS) plays a crucial role in controlling protein half-life and is essential for spermiogenesis. Recently, proteins containing ubiquitin-like domains and ubiquitin-associated domains (UBL-UBA proteins) have emerged as novel regulators within the UPS. In this study, we demonstrate that UBL7, a testis-enriched UBL-UBA protein, is indispensable for sperm formation. Deficiency of UBL7 leads to severe malformations of both the sperm tail and head. Mechanistically, UBL7 interacts with the valosin-containing protein (VCP) complex and proteasomes, and shuttles substrates between them. Notably, UBL7 slows down the degradation rates of substrates involved in endoplasmic reticulum-associated degradation (ERAD) within cells. Through a two-step immunoprecipitation method, we identify several essential factors in spermatids that are protected by UBL7, including factors involved in the development of manchette (such as IFT140), head-tail coupling apparatus (such as SPATA20) and cytoplasmic droplets (such as HK1 and SLC2a3). In summary, our findings highlight UBL7 as a guardian that protects crucial factors from excessive degradation and thereby ensures successful spermiogenesis.

Structural diversity of axonemes across mammalian motile cilia

Reproduction, development and homeostasis depend on motile cilia, whose rhythmic beating is powered by a microtubule-based molecular machine called the axoneme. Although an atomic model of the axoneme is available for the alga Chlamydomonas reinhardtii1, structures of mammalian axonemes are incomplete1-5. Furthermore, we do not fully understand how molecular structures of axonemes vary across motile-ciliated cell types in the body. Here we use cryoelectron microscopy, cryoelectron tomography and proteomics to resolve the 96-nm modular repeat of axonemal doublet microtubules (DMTs) from both sperm flagella and epithelial cilia of the oviduct, brain ventricles and respiratory tract. We find that sperm DMTs are the most specialized, with epithelial cilia having only minor differences across tissues. We build a model of the mammalian sperm DMT, defining the positions and interactions of 181 proteins including 34 newly identified proteins. We elucidate the composition of radial spoke 3 and uncover binding sites of kinases associated with regeneration of ATP and regulation of ciliary motility. We discover a sperm-specific, axoneme-tethered T-complex protein ring complex (TRiC) chaperone that may contribute to construction or maintenance of the long flagella of mammalian sperm. We resolve axonemal dyneins in their prestroke states, illuminating conformational changes that occur during ciliary movement. Our results illustrate how elements of chemical and mechanical regulation are embedded within the axoneme, providing valuable resources for understanding the aetiology of ciliopathy and infertility, and exemplifying the discovery power of modern structural biology.

Melatonin protects spermatogenic cells against DNA damage and necroptosis induced by atrazine

Atrazine (ATZ), a widely used triazine herbicide, has been shown to disrupt reproductive development in organisms. Melatonin (MLT) is a natural hormone and has been shown to have strong antioxidant properties. Due to its lipophilicity, it can cross biological barriers freely and act on germ cells directly. However, the mechanism through which melatonin affects atrazine-induced damage to male sperm cells remains unclear. This study aimed to investigate the effects of ATZ on spermatocyte development and to elucidate MLT's role in preventing ATZ-induced spermatogenesis failure. Pubertal mice were randomly divided into four groups: blank control group (Con), 5 mg/kg melatonin group (MLT), 170 mg/kg atrazine group (ATZ), and ATZ + MLT group. GC-1 cell culture was employed to access the in vitro effects of MLT and ATZ on spermatogonia. The results indicate that atrazine affected protein and metabolite composition, and reduced sperm viability, sperm motility (VAP, VSL and VCL) and levels of proteins related to spermatogenesis function in the mice testis. Melatonin alleviated the development of cellular DNA damage and necroptosis caused by atrazine both in vivo and in vitro. Moreover, we proposed that it was GC-1 cells developing necroptosis, but not other cell types in the testis. In conclusion, this study suggests that atrazine disrupts the development process, causing DNA damage in spermatozoa during spermatogenesis. Additionally, ATZ-induced necroptosis specifically targets spermatogenic cells. Notably, melatonin alleviates atrazine-induced necroptosis and DNA damage in spermatogenic cells. This study provides new insights into potential therapeutic strategies for atrazine-induced male infertility.

Achilles' heel of male infertility: good LEGO players

In a recent journal article, Chen et al. identified a germ cell-specific cofactor, STYXL1, associated with male fertility function. Deletion of STYXL1 prevents the LEGO player CCT complex from properly folding key microtubule proteins of the sperm flagellum, which affects sperm motility and male fertility function.