First published online 30 January 2008
doi: 10.1242/dev.014316
Development 135, 953-962 (2008)
Published by The Company of Biologists 2008
Formation of the embryonic-abembryonic axis of the mouse blastocyst: relationships between orientation of early cleavage divisions and pattern of symmetric/asymmetric divisions
Marcus Bischoff1,2,*,
David-Emlyn Parfitt3,* and
Magdalena Zernicka-Goetz3,
1 MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.
2 Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2
3EJ, UK.
3 The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge
CB2 1QN, UK.
View larger version (33K):
[in this window]
[in a new window]
|
Fig. 1. Four-dimensional analysis of early mouse development. Lineage
generated with SIMI Biocell. Merges of 3D representations and DIC images from
2-cell stage to blastocyst are shown (2-cell-stage descendants are red or
blue).
|
|
View larger version (32K):
[in this window]
[in a new window]
|
Fig. 2. Blastocysts show distinctive clonal patterns. (A-D) Mouse
embryos were analysed using the centres of gravity of the clones made up of
the descendants of the 8-cell-stage blastomeres. (A) Merge of DIC and 3D
representation of a blastocyst (colouring as in B). (B) Colours used to code
for the 2- and 8-cell-stage descendants. MM and EE embryos were colour-coded
by placing the first dividing cells in the left lineage. M, meridional second
cleavage division (M1 and M2 being their daughters); E, equatorial second
cleavage division; EA, EV, descendants of 4-cell blastomeres produced by
equatorial division. A, animal; V, vegetal. (C) Determining the centre of
gravity of each clone. The centroids (white dot) of the tetragons (white
dotted lines) defined by the 8-cell-stage descendants were calculated (example
shown for the blue clone). The coordinate of the mid-point of the
embryonic-abembryonic boundary (red dot) was used to align an illustration of
the cavity (white ellipse). (D) Scheme generated using the method described in
C. Each dot represents the centre of gravity of a single 8-cell clone. The
ellipse indicates cavity position and the dashed ellipse the outline of the
embryo. (E-G) Schemes representing the three different groups of
blastocysts. 8-cell clones (upper row) and 2-cell clones (lower row) use the
colour code shown in B. The frequency of each group (%) is indicated
(n=66). (E) Embryonic/abembryonic pattern. Arrowhead marks region #4.
(F) `Half-half' pattern. The dashed line indicates the separation of the
2-cell-stage clones. (G) `Mixed' pattern. (H) Schematic
embryonic/abembryonic pattern. Colour code as shown in B. Regions derived from
one 2-cell-stage blastomere are positioned in the embryonic part (left). One
region reaches slightly into the abembryonic part (asterisk). Three regions of
the other 2-cell-stage blastomere are positioned in the abembryonic part
(right) - one region (`region #4'/`dovetailed region') is positioned in the
embryonic part (#4). The embryonic-abembryonic boundary is indicated by the
dashed line. The presence of region #4 might explain the shift of this axis
(red arrow; black line).
|
|
View larger version (20K):
[in this window]
[in a new window]
|
Fig. 3. Model for the generation of blastocyst pattern. The 32-cell mouse
embryo consists of two clones derived from 2-cell blastomeres, which show an
arrangement reminiscent of a `baseball'. Based on the arrangement of
2-cell-stage clones, there are three different possibilities for the
positioning of the blastocyst cavity (white dot). (A) The cavity
develops within one clone which leads to embryonic/abembryonic pattern.
(B) The cavity forms over the border between the 2-cell-stage clones
which leads to `half-half' pattern. (C) The cavity forms more randomly
with respect to the border of the 2-cell clones generating blastocysts with
`mixed' pattern. (D) Scheme illustrating the lineage-dependency of the
different patterns. Only the embryonic-abembryonic pattern reflects the
lineage history with respect to the 2-cell stage.
|
|
View larger version (75K):
[in this window]
[in a new window]
|
Fig. 5. Analysis of division orientation. Analysis of division orientation
at the fourth and fifth cleavage divisions. (A) Percentage of
asymmetric and symmetric divisions in fourth and fifth cleavage
(average±s.e.m.). (B) Analysis of cell division orientations of
the two daughters of an asymmetric (A) or symmetric (S) division in the fourth
cleavage round. The possible permutations (shown) differ significantly
depending on the orientation of the fourth cleavage ( 2 test,
P<0.001). `I' denotes a division where both daughters lie inside
the embryo. (C,D) Proportion of asymmetric/symmetric divisions
of the 4-cell-stage descendants at fourth and fifth cleavage
(average±s.e.m.) for the four classes. (C) ME and EM embryos; (D) MM
and EE embryos. Each pair of columns represents the descendants of one of the
4-cell blastomeres (see legend of Fig.
2 for abbreviations).
|
|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
© The Company of Biologists Ltd 2008
) between the division planes of the 2-cell
blastomeres (white lines), 3D representations were rotated to assess the angle
(illustrated by the eye). (B) Scheme illustrating the measurement of the
distance of cells to the polar body (PB, see Materials and methods). (C)
Box-plot showing relationship between the four embryo classes and