Analysis of Zona-Associated Sperm as a Potential Source of Exogenous Y-DNA Interference in Sex-Typing of In Vitro-Fertilized Ovine Embryos

This study aimed to explore whether zona-associated residual sperm may contribute to exogenous Y-DNAY-DNA contamination and cause sex bias in PCR-based sex classification of ovine early-stage embryos, based on the amplification of the AMEL gene. Primers targeting the conserved regions of the ovine AMELX and AMELY genes were designed, and a nested PCR system using AMEL and YWHAZ genes was established. Group A comprised 17 female and 33 male embryos, corresponding to a female-to-male ratio of 0.52:1, whereas Group B comprised 23 female and 27 male embryos, corresponding to a female-to-male ratio of 0.85:1. DAPI staining revealed sperm-morphology structures or structures containing sperm-derived DNA adjacent to the zona pellucida of ovine early-stage embryos. Sequence alignment of PCR amplicons showed consistency with the AMELX and AMELY reference genes. In conclusion, these results support our research hypothesis that zona-associated residual sperm may serve as a potential source of Y-DNAY-DNA contamination and interfere with PCR-based embryonic sex determination.