Aneuploid abortion correlates positively with MAD1 overexpression and miR-125b down-regulation

Juan Zhao,Lijun Du,Hui Li,Guangxin Chen,Xiaoli Zhang,Min Xie,Tiansheng Cao,Haibo Li,Peiyan Xu

doi:10.1186/s13039-021-00538-1

Abstract

BackgroundAneuploidy is the most frequent cause of early-embryo abortion. Any defect in chromosome segregation would fail to satisfy the spindle assembly checkpoint (SAC) during mitosis, halting metaphase and causing aneuploidy. The mitotic checkpoint complex (MCC), comprising MAD1, MAD2, Cdc20, BUBR1 and BUB3, plays a vital role in SAC activation. Studies have confirmed that overexpression of MAD2 and BUBR1 can facilitate correct chromosome segregation and embryo stability. Research also proves that miR-125b negatively regulates MAD1 expression by binding to its 3′UTR. However, miR-125b, Mad1 and Bub3 gene expression in aneuploid embryos of spontaneous abortion has not been reported to date.MethodsIn this study, embryonic villi from miscarried pregnancies were collected and divided into two groups (aneuploidy and euploidy) based on High-throughput ligation-dependent probe amplification (HLPA) and Fluorescence in situ hybridization (FISH) analyses. RNA levels of miR-125b, MAD1 and BUB3 were detected by Quantitative real-time PCR (qRT-PCR); protein levels of MAD1 and BUB3 were analysed by Western blotting.Resultsstatistical analysis (p < 0.05) showed that miR-125b and BUB3 were significantly down-regulated in the aneuploidy group compared to the control group and that MAD1 was significantly up-regulated. Additionally, the MAD1 protein level was significantly higher in aneuploidy abortion villus, but BUB3 protein was only mildly increased. Correlation analysis revealed that expression of MAD1 correlated negatively with miR-125b.ConclusionThese results suggest that aneuploid abortion correlates positively with MAD1 overexpression, which might be caused by insufficient levels of miR-125b. Taken together, our findings first confirmed the negative regulatory mode between MAD1 and miR-125b, providing a basis for further mechanism researches in aneuploid abortion.

Highlights

Aneuploidy is a common and natural occurrence in earlyZhao et al Mol Cytogenet (2021) 14:22 imbalances are likely to cause local instability ("wreckage") at the breakpoints, which results either in partial/ whole chromosome loss or elongation of duplicated regions [5]
When the spindle assembly checkpoint (SAC) interacts with anaphase-promoting complex/cyclosome (APC/C), the latter remains inactive because Cdc20 is sequestered by Mad2 and BubR1/Bub3 in the form of a mitotic checkpoint complex (MCC)
Quantitative real‐time Polymerase chain reaction (PCR) analysis of miR‐125b, MAD1 and BUB3 RNA levels Relative mRNA expression of miR-125b and BUB3 was significantly down-regulated in the abnormal group compared to the normal group (p < 0.05), whereas MAD1 was significantly increased at the RNA level (p < 0.05) (Fig. 2)

Summary

Introduction

Aneuploidy is a common and natural occurrence in earlyZhao et al Mol Cytogenet (2021) 14:22 imbalances are likely to cause local instability ("wreckage") at the breakpoints, which results either in partial/ whole chromosome loss (e.g., aneuploidy) or elongation of duplicated regions [5]. Franck Pellestor reported that chromothripsis and chromoanasynthesis may essentially result from lagging chromosome encapsulated in micronuclei or telomere attrition and endto-end telomere fusion [6]. In this context, the spindle assembly checkpoint (SAC) is crucial to ensure chromosome segregation during mitosis. When the SAC interacts with APC/C, the latter remains inactive because Cdc is sequestered by Mad and BubR1/Bub in the form of a mitotic checkpoint complex (MCC). Any defect in chromosome segregation would fail to satisfy the spindle assembly checkpoint (SAC) during mitosis, halting metaphase and causing aneuploidy. The mitotic checkpoint complex (MCC), comprising MAD1, MAD2, Cdc, BUBR1 and BUB3, plays a vital role in SAC activation. MiR-125b, Mad and Bub gene expression in aneuploid embryos of spontaneous abortion has not been reported to date

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Conclusion