Mouse chimaeras developed from electrofused blastocysts: new evidence for developmental plasticity of the inner cell mass

Abstract

Blastocysts obtained from mice differing in pigmentation (albino versus pigmented) and the isoforms of glucose phosphate isomerase (GPI 1A versus 1B) were electrofused and those containing a single chimaeric inner cell mass (ICM) were transferred to the uterus of pseudopregnant recipients. The pups were recovered on the 20 th day by Caesarian section and fostered by females that had littered on the previous night or 24 h earlier. Altogether nine adult animals and two pups, which died soon after delivery, were available for GPI analysis. Between 9 and 13 organs/ tissues were examined and the relative contribution of the GPI 1A and 1B isoforms was estimated using an electrophoretic GPI assay. Eight adult animals were overtly chimaeric and one was chimaeric in some internal tissues only. Eight mice were males: seven were fertile, one was infertile. The ninth adult mouse was a hermaphrodite. The fertile animals produced sperm of one genotype only, i.e. derived either from the albino or from the pigmented component. This is the first report showing that adult chimaeras can be produced from two combined blastocysts, provided that fusion of the adhering trophectoderm cells is first induced and the orientation of blastocysts enables the two ICMs to integrate into a single ICM. Our results suggest that in the preimplantation blastocyst, the organisation of the ICM remains labile thus making it possible for the fused blastocysts to establish new embryonic organisation and to develop into a single organism.

Gene Expression Variations of Red—White Skin Coloration in Common Carp (Cyprinus carpio)

“…Glucose phosphate isomerase, gpi , was reported to determine the pattern of coat pigmentation in mice, suggesting that it is also a pigmentation-related gene [ 44 ]. The expression of gpib was up-regulated in white skin, with a 27-fold increase compared with red skin.…”

Mammalian and avian embryology at Warsaw University (Poland) from XIX century to the present

“…The blastocysts with single ICM develop into single chimaeric foetuses and animals. These experiments indicate that by the stage of medium sized/early expanded blastocyst, the spatial organisation (including the axis of bilateral symmetry) of ICM still remains labile (Tarkowski et al, 2005b). …”

“…However, to achieve this effect it is first necessary to induce local fusion of the trophectoderm of the two blastocysts by Sendai virus or electric impulses. Depending on the mutual position of the ICMs of the aggregated embryos, the resulting single chimaeric blastocyst can have two separate ICMs or single ICM (Tarkowski and Wojewodzka, 1982;Tarkowski et al, 2005b). After implantation, the blastocysts with two separate ICMs form two separate eggcylinders, but only some of them develop into dizygotic twin foetuses (Ozdzenski et al, 1997).…”

Morphogenesis of the mammalian blastocyst

“…These experiments indicate that no essential developmental cue is heterogeneously localized in the zygote, and all blastomeres are equivalent until the 8-cell stage. This flexibility is maintained until the early blastocyst stage since aggregation of two blastocyts leads to the formation of normal adult chimerae when the orientation of the blastocyts enables the two ICM to integrate into a single ICM (Tarkowski et al, 2005). All theses data show that mouse early development is very regulative and cannot be compared to the development of either vertebrates (Xenopus) and non vertebrates (Drosophila) embryos.…”