Distribution of descendants of first and second dividing 2-cell blastomeres when first blastomere contributes more cells to the blastocyst*
| Name (number of blastocysts) . | Total cells . | Total early . | Total embryonic . | % Embryonic early . | Early in BZ . | Early crossing BZ to abembryonic . | Total late . | Total abembryonic . | % Abembryonic late . | Late in BZ . | Late crossing BZ to embryonic . | Total BZ . | %BZ early . | %BZ late . | Tilt . |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1n (14) | 36.8 | 20.1 | 14.5 | 64 | 5.4 | 5.6 | 16.7 | 11.3 | 52 | 5.6 | 5.5 | 11.0 | 49 | 51 | 59.2 |
| 2n CD (13) | 39.3 | 20.8 | 16.5 | 67 | 6.0 | 4.2 | 18.5 | 10.9 | 60 | 5.9 | 5.9 | 11.9 | 50 | 50 | 43.3 |
| 2n PB (22) | 36.9 | 20.2 | 16.8 | 66 | 5.1 | 4.0 | 16.7 | 9.8 | 58 | 5.2 | 5.8 | 10.3 | 49 | 51 | 39.7 |
| No SEP (14) | 33.1 | 18.1 | 13.2 | 53 | 5.5 | 5.6 | 15.1 | 9.9 | 43 | 4.5 | 6.3 | 10.0 | 55 | 45 | 40.6 |
| Con SEP (17) | 31.6 | 17.6 | 13.2 | 84 | 4.2 | 2.4 | 13.9 | 9.2 | 76 | 4.9 | 2.2 | 9.1 | 45 | 55 | 30.2 |
| Name (number of blastocysts) . | Total cells . | Total early . | Total embryonic . | % Embryonic early . | Early in BZ . | Early crossing BZ to abembryonic . | Total late . | Total abembryonic . | % Abembryonic late . | Late in BZ . | Late crossing BZ to embryonic . | Total BZ . | %BZ early . | %BZ late . | Tilt . |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1n (14) | 36.8 | 20.1 | 14.5 | 64 | 5.4 | 5.6 | 16.7 | 11.3 | 52 | 5.6 | 5.5 | 11.0 | 49 | 51 | 59.2 |
| 2n CD (13) | 39.3 | 20.8 | 16.5 | 67 | 6.0 | 4.2 | 18.5 | 10.9 | 60 | 5.9 | 5.9 | 11.9 | 50 | 50 | 43.3 |
| 2n PB (22) | 36.9 | 20.2 | 16.8 | 66 | 5.1 | 4.0 | 16.7 | 9.8 | 58 | 5.2 | 5.8 | 10.3 | 49 | 51 | 39.7 |
| No SEP (14) | 33.1 | 18.1 | 13.2 | 53 | 5.5 | 5.6 | 15.1 | 9.9 | 43 | 4.5 | 6.3 | 10.0 | 55 | 45 | 40.6 |
| Con SEP (17) | 31.6 | 17.6 | 13.2 | 84 | 4.2 | 2.4 | 13.9 | 9.2 | 76 | 4.9 | 2.2 | 9.1 | 45 | 55 | 30.2 |
Distribution of dye-labelled cells in blastocysts was determined by estimating the number of cells occupying the boundary zone or crossing to the far side of the boundary zone and lying in the other part of the blastocyst,as described in Materials and Methods. The number of cells derived from the early- dividing and late-dividing 2-cell blastomere were counted by dissociating each blastocyst after 3D confocal imaging, also as described. The number of cells in embryonic and abembryonic parts, defined as being those portions of the embryonic and abembryonic regions exclusive of the boundary zone, was determined by subtracting the boundary zone and boundary zone-crossing cell number estimates from the total number of labelled cells(early or late) then adding the boundary-crossing cells from the opposite part.
Abbreviations: BZ, boundary zone between the embryonic and abembryonic parts, consisting of a layer beginning at the blastocoel surface of the ICM and extending into the embryonic region to a depth of approximately one cell(thus including both ICM and polar trophectoderm). Tilt, the approximate angle between the plane of the BZ and the plane of the clonal border (see Materials and Methods). 1n, haploid parthenogenetic embryos; 2n,diploid parthenogenetic embryos, either from cytochalasin treatment (CD) or after electrofusion (PB); no SEP, fertilised eggs with the sperm entry point(SEP) removed; Con SEP, control fertilised embryos from which a fragment of the cytoplasm was removed from an area other than the SEP.
Mean values are indicated; for full dataset see Tables 1A, 2A, 3A, 4A and 5A presented as Supplemental data.