West, John D; Tang, Pin-Chi; Everett, Clare A; MacKay, Gillian E; Flockhart, Jean H; Keighren, Margaret A. (2019). Data for re-evaluation of the causes of variation among mouse aggregation chimaeras, [dataset]. University of Edinburgh. Edinburgh Medical School. https://doi.org/10.7488/ds/2540.
The data are numerical data used to produce Figs. 2 & 5, Supplementary Figs. S3–S6 and Supplementary Table S2 in a manuscript entitled “Re-evaluation of the causes of variation among mouse aggregation chimaeras” by West JD, Tang P-C, Everett, CA, Mackay GE, Flockhart JH and Keighren MA.
The study seeks to understand why the composition of mouse aggregation chimaeras, comprising two genetically distinct cell populations, varies much more widely than that of X-inactivation mosaics. Analysis of published results for chimaeric blastocysts suggests that some variation already exists among aggregates before segregation of the ICM and TE. This would include both biological variation between aggregated embryos and experimental variation introduced by the chimaera production procedures. Variation among chimaeric ICMs was greater than among whole blastocysts, implying that significant additional variation arises when cells are allocated to the ICM or trophectoderm (TE). Moreover, in mid-gestation chimaeras, the compositions of the epiblast derivatives were not negatively correlated with the PrE derivatives, again suggesting that significant variation existed among ICMs before epiblast formation. The composition of samples from postimplantation stage chimaeras were more strongly correlated within the epiblast lineage or within the PrE lineage than between the two lineages, implying that the second allocation step, involving the segregation of the epiblast and PrE lineages, is also a significant source of variation among chimaeric epiblasts. Computer simulation results were consistent with the conclusion that the wide variation in chimaeric epiblast composition arises by two stochastic allocation steps, during the formation of the ICM and epiblast respectively. Later allocation events will cause variation among both chimaeras and X-inactivation mosaics. We also suggest that previously published U-shaped frequency distributions for chimaeric placenta composition might be explained by how TE cells are allocated to the polar TE and the subsequent movement of TE cells from the polar TE to the mural TE.
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