Embryo Growth During the Immediate Postimplantation Period

Snow, Michael

doi:10.1002/9780470720226.ch5

Cited by 35 publications

(7 citation statements)

References 26 publications

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“…We noted a tendency of the fraction of Ki67 positive cells to decrease in the ICM with further developmental progression, with a significant decrease between cyst and disk shaped ICM (Figure 5 D). Comparable patterns for the number of proliferating cells have been observed in the ectoderm, endoderm, and mesoderm of developing mouse embryos [28][29][30]. Additionally, differentiation of murine embryonic stem cells also leads to an increase in the duration of the G1 phase [33][34][35].…”

Section: Resultsmentioning

confidence: 93%

“…Since the number of mitotic cells observed was limited to individual blastocysts, we were not able to estimate a mitotic index. Depending on the exact stage and the compartment, mitotic indexes between 2 % and 18 % and estimated doubling times of 6-24h have been reported for developing mouse embryos [28][29][30]. Almost no dividing cells were observed in diapausing mouse blastocysts and the cell number remained stable [31,32].…”

Section: Resultsmentioning

confidence: 99%

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Trophectoderm and embryoblast proliferate at slow pace in the course of embryonic diapause in the roe deer (Capreolus capreolus)

Rüegg¹,

Bernal²,

Moser³

et al. 2020

Proc

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The European roe deer (Capreolus capreolus) was the first mammal in which embryonic diapause has been described. While diapause is characterized by a complete developmental arrest in some species, roe deer blastocysts show a very slow, yet continuous growth. To date, it is neither known whether this growth is accompanied by developmental progression nor whether it is uniform in both, the trophectoderm (TE) and the inner cell mass (ICM). We collected roe deer blastocysts during the regular hunting season from September 2018 to January 2019, and quantified the fraction of cells expressing the proliferation marker Ki67 by immunofluorescence and light-sheet microscopy. We found that the cell number increased from around 300 cells in September to over 20'000 cells per blastocyst in December before elongation occured. Concurrently, we observed considerable morphological changes, i.e. cavity formation and transition to a disk-like shape of the inner cell mass. During diapause, less than 10% of all cells displayed positive Ki67 staining. Strikingly, the relative increase in cell number was lower in the ICM compared to the TE, whereas the fraction of Ki67 positive cells appeared to be lower in the TE than in the ICM. Our findings thus confirm that roe deer blastocysts display developmental progression in the course of diapause. We hypothesize that while the overall duration of the cell cycle is longer in the ICM than in the TE, the fractional distribution of cell cycle phases differs, with TE cells having a longer G1 phase than cells of the ICM.

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Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Trophectoderm and embryoblast proliferate at slow pace in the course of embryonic diapause in the roe deer (Capreolus capreolus)

Rüegg¹,

Bernal²,

Moser³

et al. 2020

Proc

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“…Late replication is presented as a general property of heterochromatin, but how this property arises is unknown [ 2 ]. Additionally, embryonic development of many animals features dramatic modifications of replication timing [ 4 ][ 5 ][ 6 ][ 7 ]. In Drosophila , the length of S phase changes by over 50-fold during development [ 8 ][ 9 ][ 10 ], and in the early Drosophila embryo, the heterochromatin does not replicate later than the rest of the genome.…”

Section: Introductionmentioning

confidence: 99%

Rif1 prolongs the embryonic S phase at the Drosophila mid-blastula transition

2018

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In preparation for dramatic morphogenetic events of gastrulation, rapid embryonic cell cycles slow at the mid-blastula transition (MBT). In Drosophila melanogaster embryos, down-regulation of cyclin-dependent kinase 1 (Cdk1) activity initiates this slowing by delaying replication of heterochromatic satellite sequences and extending S phase. We found that Cdk1 activity inhibited the chromatin association of Rap1 interacting factor 1 (Rif1), a candidate repressor of replication. Furthermore, Rif1 bound selectively to satellite sequences following Cdk1 down-regulation at the MBT. In the next S phase, Rif1 dissociated from different satellites in an orderly schedule that anticipated their replication. Rif1 lacking potential phosphorylation sites failed to dissociate and dominantly prevented completion of replication. Loss of Rif1 in mutant embryos shortened the post-MBT S phase and rescued embryonic cell cycles disrupted by depletion of the S phase–promoting kinase, cell division cycle 7 (Cdc7). Our work shows that Rif1 and S phase kinases compose a replication timer controlling first the developmental onset of late replication and then the precise schedule of replication within S phase. In addition, we describe how onset of late replication fits into the progressive maturation of heterochromatin during development.

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“…This should apply, even if the cause of the lag was restricted to the preimplantation stage, as long as the time lag persists after implantation. During gastrulation, the average cell cycle time is about 5-6 h, ranging from 3-3.5 h in the primitive streak to 7-7.5 h ( Snow, 1976 , 1977 ; Mac Auley et al, 1993 ). If BALB/c embryos continue to lag behind their partner embryos, in an aggregation chimaera, by 6 to 9 h during the early postimplantation period, BALB/c epiblast cells will lag at least a whole cell cycle behind and so would contribute significantly less to the chimaera.…”

Section: Discussionmentioning

confidence: 99%

Selection against BALB/c strain cells in mouse chimaeras

et al. 2018

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It has been shown previously that BALB/c strain embryos tend to contribute poorly to mouse aggregation chimaeras. In the present study we showed that BALB/c cells were not preferentially allocated to any extraembryonic lineages of mouse aggregation chimaeras, but their contribution decreased during the early postimplantation period and they were significantly depleted by E8.5. The development of BALB/c strain preimplantation embryos lagged behind embryos from some other strains and the contribution that BALB/c and other embryos made to chimaeras correlated with their developmental stage at E2.5. This relationship suggests that the poor contribution of BALB/c embryos to aggregation chimaeras is at least partly a consequence of generalised selection related to slow or delayed preimplantation development. The suitability of BALB/c embryos for maximising the ES cell contribution to mouse ES cell chimaeras is also discussed.

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Embryo Growth During the Immediate Postimplantation Period

Cited by 35 publications

References 26 publications

Trophectoderm and embryoblast proliferate at slow pace in the course of embryonic diapause in the roe deer (Capreolus capreolus)

Trophectoderm and embryoblast proliferate at slow pace in the course of embryonic diapause in the roe deer (Capreolus capreolus)

Rif1 prolongs the embryonic S phase at the Drosophila mid-blastula transition

Selection against BALB/c strain cells in mouse chimaeras

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