A global priority for ameliorating male factor infertility includes identification of environmental factors and mechanisms that impact sperm function. Detection of endocrine disrupting chemicals (EDC) in seminal plasma and within the female reproductive tract has created an urgent need to understand how environmental stressors alter postejaculatory sperm function. Tributyltin chloride (TBT) is an EDC and epigenetic modifier that causes reproductive disorders. The consequences of TBT exposure on postejaculatory sperm remain unknown. The present study was aimed at identifying structural, genomic, and epigenomic consequences of TBT exposure to postejaculatory sperm. Bovine sperm were exposed to TBT (0, 1, 10, 100 nM) for 24 h followed by quantification of sperm kinematics, DNA integrity, and methylation status. No differences were detected in sperm kinematics or capacitation status. However, acrosome integrity was compromised at both 0 and 24 h (P ≤ 0.05). Sperm DNA integrity was also negatively affected after 24 h. Whole-genome methyl-seq revealed ~750 differentially methylated regions (DMRs) associated with exposure to TBT. Ingenuity Pathway Analyses and Gene Ontology identified embryo development, cell signaling, and transcriptional regulation as the most relevant bio-functions of TBT altered DMRs. In conclusion, postejaculatory mammalian sperm exposure to TBT negatively affected parameters important for sperm function while altering DNA integrity and the methylation profile of gene promoter regions. Consequences of sperm exposure to TBT included cellular and molecular mechanisms that are important for sperm function but remain undetected by routine clinical analyses. These findings provide new insight into environmental impacts on postejaculatory sperm structure and function.
Siddique et al. (Mon,) studied this question.