Restricted Distribution of Tetraploid Cells in Mouse Tetraploid ↔ Diploid Chimaeras

• Published in: Developmental biology 1995, Vol.167 (1), p.213-226
• Main Authors: James, Roberta M., Klerkx, Anke H.E.M., Keighren, Margaret, Flockhart, Jean H., West, John D.
• Format: Article
• Language: English
• Subjects: Animals; Chimera; Diploidy; Ectoderm - physiology; Embryonic and Fetal Development; Endoderm - physiology; Female; Mice; Mice, Inbred Strains; Polyploidy
• ISSN: 0012-1606; 1095-564X
• DOI: 10.1006/dbio.1995.1018

Tetraploid mouse embryos were produced by electrofusion at the 2-cell stage, cultured overnight, and aggregated with normal diploid embryos to produce tetraploid↔diploid (4 n ↔ 2 n) chimaeric conceptuses. At 7 1 2 days the 4 n ↔ 2 n chimaeras were usually smaller and developmentally retarded compared to control diploid↔diploid chimaeras. At 12 1/2 days the 4 n ↔ 2 n chimaeras had heavier placentas but there was no significant difference in fetal size. Tetraploid cells showed a restricted tissue distribution at both developmental stages studied: 4 n cells were commonly present in both the primitive endoderm and the trophectoderm lineages but they rarely contributed to the primitive ectoderm lineage. The overall similarity in the distribution of tetraploid cells at 7 1 2 and 12 1 2 days implies that whatever causes the restricted tissue distribution operates largely before 7 1 2 days. There was no evidence for excessive embryonic losses of 4 n ↔ 2 n chimaeras. So, if the restricted distribution of 4 n cells was a result of cell selection, the mechanism is more likely to involve loss of 4 n cells from the primitive ectoderm early in development rather than selective death of conceptuses with tetraploid cells in this lineage. Alternatively, 4 n cells may be preferentially allocated to the trophectoderm and primitive endoderm rather than the primitive ectoderm layer at the blastocyst stage.