Single-blastomere next-generation sequencing confirms chromosomal abnormalities as the primary cause of impaired developmental potential in embryos with abnormal cleavage patterns

Abstract

Abnormal cleavage impairs embryonic development, but the effects of different abnormal cleavage patterns and occurrence stages remain unclear. Previous chromosomal analyses at the blastocyst stage have failed to elucidate the underlying mechanism. This study investigated the effects of abnormal cleavage patterns and occurrence stages on embryonic developmental potential and clarified the association between abnormal cleavage and chromosomal abnormalities through single-blastomere sequencing. Time-lapse data were retrospectively analysed to assess embryonic development. The embryos were divided into normal cleavage (NC), direct cleavage (DC), chaotic cleavage (CC), reverse cleavage (RC) and multinucleation (MN) groups based on their cleavage patterns and into subgroups 1, 2 and 3 based on the first three division cycles of abnormal cleavage. To establish a novel single-blastomere continuous culture and isolation (SBCCI) system, 2PN zygotes derived from in vitro-matured MI oocytes were prospectively collected. Following zona pellucida removal, they were monitored via time-lapse. During the first three division cycles, blastomeres exhibiting different cleavage patterns were subjected to next-generation sequencing to analyse their chromosomal status at the single-blastomere level. Compared with the normal cleavage group, the abnormal cleavage group presented significantly lower developmental indicators (all P < 0.05). The blastocyst and high-quality blastocyst formation rates were significantly lower in the DC and CC groups than in the RC and MN groups (all P < 0.05). The DC1 and RC1 subgroups had significantly lower blastocyst formation rates than the DC2/3 and RC2/3 subgroup (all P < 0.05). The amplification success rate in the CC group and the detection success rate in the DC group were significantly lower than those in the other groups (all P < 0.05). The chromosomal abnormality rate was significantly greater in the abnormal cleavage groups than in the normal cleavage group ( P < 0.05). The chromosomal abnormality rates were the highest in the DC and CC groups (100.00% and 86.96%, respectively). The euploidy rates were significantly lower in the NC1 group than in the NC3 group ( P < 0.05). Abnormal cleavage can significantly impair embryonic development, and its effects vary depending on the pattern and occurrence stage. Critically, we demonstrated that chromosomal abnormalities induced by abnormal cleavage are negatively associated with embryonic development.