The contribution of tetraploid cells to mid-gestation mouse aggregation chimaeras

• Main Author: James, Roberta Margaret
• Published: University of Edinburgh 1993
• Subjects: 571.861
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.652939

Mouse aggregation chimaeras were used in this study to attempt to evaluate the developmental potential of tetraploid cells in the fetus and extraembryonic membranes of mid-gestation chimaeric conceptuses. Diploid͍diploid chimaeras were generated and analysed to provide a control and general baseline for the analysis of tetraploid͍diploid chimaeras. Relationships between compositions of tissues in the diploid͍diploid chimaeras were in agreement with those already established. Tetraploid embryos were produced by electrofusion, which facilitates the fusion of adjacent blastomeres following the exposure to electric field pulses. Three genetic cell markers were chosen to allow identification of the two cell populations in chimaeric conceptuses. These were; (i) pigment in the retinal epithelial cells of the eye; (ii) electrophoretic variants of the enzyme glucose phosphate isomerase (GPI); (iii) the β-globin transgenic marker, which can be detected by <i>in situ</i> hybridization. The bulk of the analysis was performed at 12<SUP>1</SUP>/<SUB>2</SUB> days of gestation by assaying homogenized tissue for GPI. By constructing chimaeras from two embryos which were homozygous for different alleles of <i>Gpi-1</i>, it was possible to estimate the proportions of each cell type in each tissue of the chimaera. <i>In situ</i> hybridization was used to provide spatial information on the yolk sacs of the tetraploid͍diploid chimaeras. The efficiency of the electrofusion technique was tested by <i>in situ</i> hybridization, to ensure that embryos produced by the technique were uniformly tetraploid and not 4m/2n mosaics. In the tetraploid͍diploid chimaeras, the tetraploid cells contributed mainly to the primitive endoderm derivatives (yolk sac endoderm, parietal; endoderm), with very little contribution to the primitive ectoderm derivatives (fetus, amnion, yolk sac mesoderm). There was also good colonisation of the trophectoderm derivatives (trophoblast, placenta).