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Spermatogenesis starts with the onset of puberty within the seminiferous epithelium of the testes. It is a complex process under intricate control of the endocrine system. Physiological regulations by steroid hormones in general and by estrogens in particular are due to their chemical nature prone to be disrupted by exogenous factors acting as endocrine disruptors (EDs). 17α-Ethynylestradiol (EE2) is an environmental pollutant with a confirmed ED activity and a well-known effect on spermatogenesis and chromatin remodeling in haploid germ cells. The aim of our study was to assess possible effects of two doses (2.5ng/ml; 2.5 μg/ml) of EE2 on both histone-to-protamine exchange and epigenetic profiles during spermatogenesis performing a multi/transgenerational study in mice. Our results demonstrated an impaired histone-to-protamine exchange with a significantly higher histone retention in sperm nuclei of exposed animals, when this process was accompanied by the changes of histone post-translational modifications (PTMs) abundancies with a prominent effect on H3K9Ac and partial changes in protamine 1 promoter methylation status. Furthermore, individual changes in molecular phenotypes were partially transmitted to subsequent generations, when no direct trans-generational effect was observed. Finally, the uncovered specific localization of the histone retention in sperm nuclei and their specific PTMs profile after EE2 exposure may indicate an estrogenic effect on sperm motility and early embryonic development via epigenetic mechanisms., (© 2024. The Author(s).)

Background: In rodents, the cell surface complement regulatory protein CD46 is expressed solely on the spermatozoal acrosome membrane. Ablation of the CD46 gene is associated with a faster acrosome reaction. Sperm from Apodemus flavicollis (yellow-necked field mice), A. microps (pygmy field mice) and A. sylvaticus (European wood mice) fail to express CD46 protein and exhibit a more rapid acrosome reaction rate than Mus (house mice) or BALB/c mice. A. agrarius (striped field mice) belong to a different Apodemus subgenus and have pronounced promiscuity and large relative testis size. The aim of this study was to determine whether A. agrarius sperm fail to express CD46 protein and, if so, whether A. agrarius have a faster acrosome reaction than Mus., Methods: Reverse transcription polymerase chain reaction (RT-PCR) was used to assess whether A. agrarius transcribe testicular CD46 mRNA. RT-PCR was supplemented with 3'- and 5'-rapid amplification of cDNA ends to determine the complete nucleotide sequence of A. agrarius CD46. Fluorescence microscopy was used to assess whether CD46 protein is expressed by A. agrarius sperm. The acrosome status of A. agrarius sperm was calculated over time by immunocytochemistry using peanut agglutinin lectin., Results: We demonstrate that A. agrarius mice transcribe two unique alternatively spliced testicular CD46 mRNA transcripts, both lacking exon 7, which differ from those described previously in other Apodemus species. The larger A. agrarius CD46 transcript has an insert between exons 10 and 11 which, if translated, would result in a novel cytoplasmic tail. In addition, A. agrarius CD46 transcripts have an extended AU-rich 3'-untranslated region (UTR) and a truncated 5'-UTR, resulting in failure to express spermatozoal CD46 protein. We show that A. agrarius has a significantly faster spontaneous acrosome reaction rate than A. sylvaticus and Mus., Conclusion: Absence of CD46 protein expression is associated with acrosomal instability in rodents. A. agrarius mice express novel CD46 transcripts, resulting in the trade of spermatozoal CD46 protein expression for a rapid acrosome reaction rate, in common with other species of field mice. This provides a strategy to increase competitive sperm advantage for individuals, leading to faster fertilisation in this highly promiscuous genus.