Mouse model of chromosome mosaicism reveals lineage-specific depletion of aneuploid cells and normal developmental potential.

Most human pre-implantation embryos are mosaics of euploid and aneuploid cells. To determine the fate of aneuploid cells and the developmental potential of mosaic embryos, here we generate a mouse model of chromosome mosaicism. By treating embryos with a spindle assembly checkpoint inhibitor during the four- to eight-cell division, we efficiently generate aneuploid cells, resulting in embryo death during peri-implantation development. Live-embryo imaging and single-cell tracking in chimeric embryos, containing aneuploid and euploid cells, reveal that the fate of aneuploid cells depends on lineage: aneuploid cells in the fetal lineage are eliminated by apoptosis, whereas those in the placental lineage show severe proliferative defects. Overall, the proportion of aneuploid cells is progressively depleted from the blastocyst stage onwards. Finally, we show that mosaic embryos have full developmental potential, provided they contain sufficient euploid cells, a finding of significance for the assessment of embryo vitality in the clinic.We acknowledge the Wellcome Trust for supporting this work. H.B was supported by a Wellcome Trust clinical PhD fellowship. We acknowledge the Research Foundation Flanders (FWO) (FWO-G.A093.11 and FWO-G.0924.15 to T.V.; the travel grant V.4.140.10.N.00 to T.V.; N.V.d.A., E.F.G. and K.T. are Ph.D. students supported by FWO 1.1.H.28.12, FWO G.0924.15 and FWO 1126016N, respectively) and KU Leuven SymBioSys (PFV/10/016 to T.V.; P.K. is a PhD. student supported with PFV/10/016).This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/ncomms1116

Effect of day 3 embryo morphometrics and morphokinetics on survival and implantation after slow freezing-thawing and after vitrification-warming: a retrospective cohort study

Morphometric and morphokinetic evaluation of in vitro cultured human embryos allows evaluation without time restriction and reduces intra- and inter-observer variability. Even though these technologies have been reported to improve the quality of cleavage stage embryo evaluation during fresh culture, possible advantages in the evaluation of cryopreserved embryos have been scarcely explored. This study aims to compare morphometric and morphokinetic parameters between slow frozen and vitrified embryos and to determine their relationship to embryo survival and implantation rate (IR) after thawing/warming.status: publishe

Effect of embryo morphology and morphometrics on implantation of vitrified day 3 embryos after warming: a retrospective cohort study

Characteristics routinely used to evaluate embryo quality after thawing include number of blastomeres survived and presence of mitosis resumption after overnight culture. It is unknown to which extent symmetry and fragmentation affect implantation after warming and whether application of stricter criteria either before vitrification or after warming would improve implantation rate (IR) of vitrified/warmed embryos. This study aimed to find new parameters to improve selection criteria for vitrification and for transfer after warming.status: publishe

PREIMPLANTATION GENETIC TESTING: Single-cell technologies at the forefront of PGT and embryo research.

While chromosomal mosaicism in the embryo was observed already in the 1990s using both karyotyping and FISH technologies, the full extent of this phenomenon and the overall awareness of the consequences of chromosomal instability on embryo development has only come with the advent of sophisticated single-cell technologies. High-throughput techniques, such as DNA microarrays and massive parallel sequencing, have shifted single-cell genome research from evaluating a few loci at a time to the ability to perform comprehensive screening of all 24 chromosomes. The development of genome-wide single-cell haplotyping methods have also enabled for simultaneous detection of single-gene disorders and aneuploidy using a single universal protocol. Today, three decades later haplotyping-based embryo testing is performed worldwide to reliably detect virtually any Mendelian hereditary disease with a known cause, including autosomal-recessive, autosomal-dominant and X-linked disorders. At the same time, these single-cell assays have also provided unique insight into the complexity of embryo genome dynamics, by elucidating mechanistic origin, nature and developmental fate of embryonic aneuploidy. Understanding the impact of postzygotically acquired genomic aberrations on embryo development is essential to determine the still controversial diagnostic value of aneuploidy screening. For that reason, considerable efforts have been put into linking the genetic constitution of the embryo not only to its morphology and implantation potential, but more importantly to its transcriptome using single-cell RNA sequencing. Collectively, these breakthrough technologies have revolutionized single-cell research and clinical practice in assisted reproduction and led to unique discoveries in early embryogenesis.status: publishe

Vitrification of cleavage stage day 3 embryos results in higher live birth rates than conventional slow freezing: a RCT

Is the live birth rate (LBR) per embryo thawed/warmed higher when Day 3 cleavage stage embryos are cryopreserved by vitrification compared with slow freezing?status: publishe

Mouse model of chromosome mosaicism reveals lineage-specific depletion of aneuploid cells and normal developmental potential

Most human pre-implantation embryos are mosaics of euploid and aneuploid cells. To determine the fate of aneuploid cells and the developmental potential of mosaic embryos, here we generate a mouse model of chromosome mosaicism. By treating embryos with a spindle assembly checkpoint inhibitor during the four- to eight-cell division, we efficiently generate aneuploid cells, resulting in embryo death during peri-implantation development. Live-embryo imaging and single-cell tracking in chimeric embryos, containing aneuploid and euploid cells, reveal that the fate of aneuploid cells depends on lineage: aneuploid cells in the fetal lineage are eliminated by apoptosis, whereas those in the placental lineage show severe proliferative defects. Overall, the proportion of aneuploid cells is progressively depleted from the blastocyst stage onwards. Finally, we show that mosaic embryos have full developmental potential, provided they contain sufficient euploid cells, a finding of significance for the assessment of embryo vitality in the clinic.status: publishe

Mouse Model of Chromosome Mosaicism Reveals Lineage-Specific Depletion of Aneuploid Cells and Normal Developmental Potential

This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/ncomms11165Most human pre-implantation embryos are mosaics of euploid and aneuploid cells. To determine the fate of aneuploid cells and the developmental potential of mosaic embryos, here we generate a mouse model of chromosome mosaicism. By treating embryos with a spindle assembly checkpoint inhibitor during the four- to eight-cell division, we efficiently generate aneuploid cells, resulting in embryo death during peri-implantation development. Live-embryo imaging and single-cell tracking in chimeric embryos, containing aneuploid and euploid cells, reveal that the fate of aneuploid cells depends on lineage: aneuploid cells in the fetal lineage are eliminated by apoptosis, whereas those in the placental lineage show severe proliferative defects. Overall, the proportion of aneuploid cells is progressively depleted from the blastocyst stage onwards. Finally, we show that mosaic embryos have full developmental potential, provided they contain sufficient euploid cells, a finding of significance for the assessment of embryo vitality in the clinic.We acknowledge the Wellcome Trust for supporting this work. H.B was supported by a Wellcome Trust clinical PhD fellowship. We acknowledge the Research Foundation Flanders (FWO) (FWO-G.A093.11 and FWO-G.0924.15 to T.V.; the travel grant V.4.140.10.N.00 to T.V.; N.V.d.A., E.F.G. and K.T. are Ph.D. students supported by FWO 1.1.H.28.12, FWO G.0924.15 and FWO 1126016N, respectively) and KU Leuven SymBioSys (PFV/10/016 to T.V.; P.K. is a PhD. student supported with PFV/10/016)

Tracing the origin of disseminated tumor cells in breast cancer using single-cell sequencing

Background Single-cell micro-metastases of solid tumors often occur in the bone marrow. These disseminated tumor cells (DTCs) may resist therapy and lay dormant or progress to cause overt bone and visceral metastases. The molecular nature of DTCs remains elusive, as well as when and from where in the tumor they originate. Here, we apply single-cell sequencing to identify and trace the origin of DTCs in breast cancer. Results We sequence the genomes of 63 single cells isolated from six non-metastatic breast cancer patients. By comparing the cells’ DNA copy number aberration (CNA) landscapes with those of the primary tumors and lymph node metastasis, we establish that 53% of the single cells morphologically classified as tumor cells are DTCs disseminating from the observed tumor. The remaining cells represent either non-aberrant “normal” cells or “aberrant cells of unknown origin” that have CNA landscapes discordant from the tumor. Further analyses suggest that the prevalence of aberrant cells of unknown origin is age-dependent and that at least a subset is hematopoietic in origin. Evolutionary reconstruction analysis of bulk tumor and DTC genomes enables ordering of CNA events in molecular pseudo-time and traced the origin of the DTCs to either the main tumor clone, primary tumor subclones, or subclones in an axillary lymph node metastasis. Conclusions Single-cell sequencing of bone marrow epithelial-like cells, in parallel with intra-tumor genetic heterogeneity profiling from bulk DNA, is a powerful approach to identify and study DTCs, yielding insight into metastatic processes. A heterogeneous population of CNA-positive cells is present in the bone marrow of non-metastatic breast cancer patients, only part of which are derived from the observed tumor lineages