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Analysis of bovine blastocysts indicates ovarian stimulation does not induce chromosome errors, nor discordance between inner-cell mass and trophectoderm lineages

Tutt, D.A.R., Silvestri, G., Serrano-Albal, M., Simmons, R.J., Kwong, W.Y., Guven-Ates, G., Canedo-Ribeiro, C., Labrecque, R., Blondin, P., Handyside, A.H., and others. (2021) Analysis of bovine blastocysts indicates ovarian stimulation does not induce chromosome errors, nor discordance between inner-cell mass and trophectoderm lineages. Theriogenology, 161 . pp. 108-119. ISSN 0093-691X. (doi:10.1016/j.theriogenology.2020.11.021) (KAR id:84728)


Contemporary systems for oocyte retrieval and culture of both cattle and human embryos are suboptimal with respect to pregnancy outcomes following transfer. In humans, chromosome abnormalities are the leading cause of early pregnancy loss in assisted reproduction. Consequently, pre-implantation genetic testing for aneuploidy (PGT-A) is widespread and there is considerable interest in its application to identify suitable cattle IVP embryos for transfer. Here we report on the nature and extent of chromosomal abnormalities following transvaginal follicular aspiration (OPU) and IVP in cattle. Nine sexually mature Holstein heifers underwent nine sequential cycles of OPU-IVP (six non-stimulated and three stimulated cycles), generating 459 blastocysts from 783 oocytes. We adopted a SNP-array approach normally employed in genomic evaluations but reanalysed (Turner et al., 2019; Theriogenology 125: 249) to detect levels of meiotic aneuploidy. Specifically, we asked whether ovarian stimulation increased the level of aneuploidy in either trophectoderm (TE) or inner-cell mass (ICM) lineages of blastocysts generated from OPU-IVP cycles. The proportion of Day 8 blastocysts of inseminated was greater (P < 0.001) for stimulated than non-stimulated cycles (0.712 ± 0.0288 vs. 0.466 ± 0.0360), but the overall proportion aneuploidy was similar for both groups (0.241 ± 0.0231). Most abnormalities consisted of meiotic trisomies. Twenty in vivo derived blastocysts recovered from the same donors were all euploid, thus indicating that 24 h of maturation is primarily responsible for aneuploidy induction. Chromosomal errors in OPU-IVP blastocysts decreased (P < 0.001) proportionately as stage/grade improved (from 0.373 for expanded Grade 2 to 0.128 for hatching Grade 1 blastocysts). Importantly, there was a high degree of concordance in the incidence of aneuploidy between TE and ICM lineages. Proportionately, 0.94 were “perfectly concordant” (i.e. identical result in both); 0.01 were imperfectly concordant (differing abnormalities detected); 0.05 were discordant; of which 0.03 detected a potentially lethal TE abnormality (false positives), leaving only 0.02 false negatives. These data support the use of TE biopsies for PGT-A in embryos undergoing genomic evaluation in cattle breeding. Finally, we report chromosome-specific errors and a high degree of variability in the incidence of aneuploidy between donors, suggesting a genetic contribution that merits further investigation.

Item Type: Article
DOI/Identification number: 10.1016/j.theriogenology.2020.11.021
Uncontrolled keywords: Aneuploidy, Cattle, Ovarian stimulation, In vitro culture, Blastocyst, Biopsy
Subjects: Q Science
Divisions: Divisions > Division of Natural Sciences > Biosciences
Signature Themes: Food Systems, Natural Resources and Environment
Depositing User: Giuseppe Silvestri
Date Deposited: 08 Dec 2020 10:36 UTC
Last Modified: 04 Mar 2024 19:14 UTC
Resource URI: (The current URI for this page, for reference purposes)

University of Kent Author Information

Silvestri, G..

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Handyside, A.H..

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Griffin, D.K..

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