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We consider the problem of landmark matching between two unlabelled point sets, in particular where the number of points in each cloud may differ, and where points in each cloud may not have a corresponding match. We invoke a Bayesian framework to identify the transformation of coordinates that maps one cloud to the other, alongside correspondence of the points. This problem necessitates a novel methodology for Bayesian data selection, simultaneous inference of model parameters, and selection of the data which leads to the best fit of the model to the majority of the data. We apply this to a problem in developmental biology where the landmarks correspond to segmented cell centres, where potential death or division of cells can lead to discrepancies between the point-sets from each image. We validate the efficacy of our approach using in silico tests and a microinjected fluorescent marker experiment. Subsequently we apply our approach to the matching of cells between real time imaging and immunostaining experiments, facilitating the combination of single-cell data between imaging modalities. Furthermore our approach to Bayesian data selection is broadly applicable across data science, and has the potential to change the way we think about fitting models to data. [ABSTRACT FROM AUTHOR]

One of the unanswered questions in mammalian development is how the embryonic-abembryonic axis of the blastocyst is first established. It is possible that the first cleavage division contributes to this process, because in most mouse embryos the progeny of one two-cell blastomere primarily populate the embryonic part of the blastocyst and the progeny of its sister populate the abembryonic part. However, it is not known whether the embryonic-abembryonic axis is set up by the first cleavage itself, by polarity in the oocyte that then sets the first cleavage plane with respect to the animal pole, or indeed whether it can be divorced entirely from the first cleavage and established in relation to the animal pole. Here we test the importance of the orientation of the first cleavage by imposing an elongated shape on the zygote so that the division no longer passes close to the animal pole, marked by the second polar body. Non-invasive lineage tracing shows that even when the first cleavage occurs along the short axis imposed by this experimental treatment, the progeny of the resulting two-cell blastomeres tend to populate the respective embryonic and abembryonic parts of the blastocyst. Thus, the first cleavage contributes to breaking the symmetry of the embryo, generating blastomeres with different developmental characteristics. [ABSTRACT FROM AUTHOR]

The conservation of early cleavage patterns in organisms as diverse as echinoderms and mammals suggests that even in highly regulative embryos such as the mouse, division patterns might be important for development. Indeed, the first cleavage divides the fertilized mouse egg into two cells: one cell that contributes predominantly to the embryonic part of the blastocyst, and one that contributes to the abembryonic part. The zygotes of organisms as diverse as echinoderms and mammals follow stereotyped patterns of early cleavage division. This conservation suggests that, even in highly regulative embryos such as the mouse, division patterns are important in development. Here we show, by removing, transplanting or duplicating the animal or vegetal poles of the mouse egg, that a spatial cue at the animal pole orients the plane of this initial division. Embryos with duplicated animal, but not vegetal, poles show abnormalities in chromosome segregation that compromise their development. Our results show that localized factors in the mammalian egg orient the spindle and so define the initial cleavage plane. In increased dosage, however, these factors are detrimental to the correct execution of division. [ABSTRACT FROM AUTHOR]

Pluripotent embryonic stem cells (ESCs) can be derived from blastocyst-stage mouse embryos. However, the exact in vivo counterpart of ESCs has remained elusive. A combination of expression profiling and stem cell derivation identifies epiblast cells from late-stage blastocysts as the source, and functional equivalent, of ESCs. [ABSTRACT FROM AUTHOR]

Hiiragi et al. compare our model of the developing mouse egg with theirs. They seem to present patterning as equivalent to determination, but this is confusing as patterning does not have to mean determination. We have never stated that mouse embryo development is determined. Mouse development is regulative rather than determinative, and this can be explained in two ways: first, development could be entirely unbiased, generating identical cells; second, there could be some developmental bias or, in other words, pattern from the beginning that is not constraining. There is evidence for early bias from several laboratories but this does not mean that cells have localized determinants fixing their fates. Regulative development does not exclude bias, which indicates inclination, not determination. [ABSTRACT FROM AUTHOR]