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Nuclear DNA fragmentation negatively affects zona binding competence of Y bearing mouse spermatozoa
Dayanidhi Kumar1, Dinesh Upadhya, Shubhashree Uppangala
1Division of Clinical Embryology, Department of Obstetrics & Gynecology, Kasturba Medical College, Manipal University, Manipal, 576 104, India.
Purpose:
To investigate the influence of sperm DNA integrity on the zona binding ability of mouse spermatozoa in relation to their sex chromosomal constitution.
Method(S):
In this prospective experimental study, the sperm DNA fragmentation was induced by exposing testicular area of Swiss Albino mice (Mus musculus) to different doses of γ-radiation (0, 2.5, 5.0 and 10.0 Gy). Sperm DNA fragmentation was quantified by single cell gel electrophoresis (comet assay). In vitro sperm zona binding assay was performed and the numbers of zona bound X and Y bearing spermatozoa were determined using fluorescence in situ hybridization (FISH).
Result(S):
The assessment of zona pellucida bound X and Y-bearing spermatozoa using fluorescence in situ hybridization has revealed a unique binding pattern. The number of zona bound Y-spermatozoa declined significantly (P < 0.01 to 0.0001) with increase in the DNA damage. The skewed binding pattern of X and Y-bearing sperm was strongly correlated with the extent of sperm DNA damage.
Conclusion(S):
The zona pellucida may have a role in preventing DNA damaged mouse sperm binding especially towards Y-bearing sperm. However, the exact mechanism behind this observation needs to be elucidated further.
Insights
Sperm DNA damage significantly impacts sperm
Area of Science:
- Reproductive Biology
- Genetics
- Toxicology
Background:
- Sperm DNA integrity is crucial for male fertility.
- Spermatozoa carry either X or Y chromosomes, determining offspring sex.
- Radiation exposure can induce sperm DNA fragmentation.
Purpose of the Study:
- To examine how sperm DNA integrity affects sperm's ability to bind to the zona pellucida.
- To investigate this in relation to the sperm's sex chromosomal constitution (X or Y).
Main Methods:
- Sperm DNA fragmentation was induced in mice using varying doses of gamma radiation.
- DNA fragmentation was measured using the comet assay.
- Sperm binding to the zona pellucida was assessed in vitro, with X and Y-bearing sperm identified via fluorescence in situ hybridization (FISH).
Main Results:
- Increased DNA damage in sperm led to a significant decrease in the number of Y-chromosome-bearing sperm binding to the zona pellucida.
- A strong correlation was observed between the degree of DNA damage and the skewed binding pattern of X and Y-bearing sperm.
- FISH analysis revealed distinct binding patterns influenced by DNA integrity.
Conclusions:
- The zona pellucida may act as a barrier, preventing DNA-damaged sperm, particularly Y-bearing sperm, from binding.
- Further research is needed to understand the precise mechanisms behind this selective binding phenomenon.
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