Zinc is an intracellular signal during sperm activation in Caenorhabditis elegans

Toxic effects and potential mechanisms of zinc pyrithione (ZPT) exposure on sperm and testicular injury in zebrafish

Zinc pyrithione (ZPT) is widely recognized for its beneficial properties as an antifouling, antibacterial, and antifungal agent. Despite its positive industrial contributions, ZPT has been proven to exhibit toxicity towards various ecosystems, particularly affecting marine life. However, there is still a dearth of comprehensive research on ZPT toxicity and its toxicological mechanism in reproductive systems of aquatic organisms. In our study, we conducted a thorough analysis and unveiled a multitude of abnormalities in zebrafish sperm and testicular tissue caused by ZPT exposure, including a dose-dependent diminishing of testosterone levels, various sperm deformities, decreased sperm concentration and motility, and ROS-induced testicular tissue DNA damage. In addition, our study suggested that ZPT-induced testicular damage is associated with heightened oxidative stress, apoptosis, and possible hyperpolarization of the mitochondrial membrane. Through RNA-seq analysis, a total of 409 DEGs associated with ZPT-induced testicular injury were identified, and the hub gene was determined using a protein-protein interaction network (PPI). The genes and pathways uncovered in this study point to potential mechanisms of ZPT exposure on sperm and testicular injury in zebrafish.

Spermiogenesis in Caenorhabditis elegans: An Excellent Model to Explore the Molecular Basis for Sperm Activation

C. elegans spermiogenesis converts non-motile spermatids into motile, fertilization-competent spermatozoa. Two major events include the building of a pseudopod required for motility and fusion of membranous organelles (MOs)-intracellular secretory vesicles-with the spermatid plasma membrane required for the proper distribution of sperm molecules in mature spermatozoa. The mouse sperm acrosome reaction-a sperm activation event occurring during capacitation-is similar to MO fusion in terms of cytological features and biological significance. Moreover, C. elegans fer-1 and mouse Fer1l5, both encoding members of the ferlin family, are indispensable for MO fusion and acrosome reaction, respectively. Genetics-based studies have identified many C. elegans genes involved in spermiogenesis pathways; however, it is unclear whether mouse orthologs of these genes are involved in the acrosome reaction. One significant advantage of using C. elegans for studying sperm activation is the availability of in vitro spermiogenesis, which enables combining pharmacology and genetics for the assay. If certain drugs can activate both C. elegans and mouse spermatozoa, these drugs would be useful probes to explore the mechanism underlying sperm activation in these two species. By analyzing C. elegans mutants whose spermatids are insensitive to the drugs, genes functionally relevant to the drugs' effects can be identified.

Zinc transporters ZIPT-2.4 and ZIPT-15 are required for normal C. elegans fecundity

PURPOSE

The requirement of zinc for the development and maturation of germ lines and reproductive systems is deeply conserved across evolution. The nematode Caenorhabditis elegans offers a tractable platform to study the complex system of distributing zinc to the germ line. We investigated several zinc importers to investigate how zinc transporters play a role in the reproductive system in nematodes, as well as establish a platform to study zinc transporter biology in germline and reproductive development.

METHODS

Previous high throughput transcriptional datasets as well as phylogenetic analysis identified several putative zinc transporters that have a function in reproduction in worms. Phenotypic analysis of CRISPR-generated knockouts and tags included characterization of offspring output, gonad development, and protein localization. Light and immunofluorescence microscopy allowed for visualization of physiological and molecular effects of zinc transporter mutations.

RESULTS

Disruption of two zinc transporters, ZIPT-2.4 and ZIPT-15, was shown to lead to defects in reproductive output. A mutation in zipt-2.4 has subtle effects on reproduction, while a mutation in zipt-15 has a clear impact on gonad and germline development that translates into a more pronounced defect in fecundity. Both transporters have germline expression, as well as additional expression in other cell types.

CONCLUSIONS

Two ZIP-family zinc transporter orthologs of human ZIP6/10 and ZIP1/2/3 proteins are important for full reproductive fecundity and participate in development of the gonad. Notably, these zinc transporters are present in gut and reproductive tissues in addition to the germ line, consistent with a complex zinc trafficking network important for reproductive success.