On the cellular and developmental lethality of a Xenopus nucleocytoplasmic hybrid

Abstract

Nucleocytoplasmic hybrid (cybrid) embryos result from the combination of the nucleus of one species, and the egg cytoplasm of another species. Cybrid embryos can be obtained either in the haploid state by the cross-fertilization or intra-cytoplasmic injection of an enucleated egg with sperm from another species, or in the diploid state by the technique of interspecies somatic cell nuclear transfer (iSCNT). Cybrids that originate from the combination of the nucleus and the cytoplasm of distantly related species commonly expire during early embryonic development, and the cause of this arrest is currently under investigation. Here we show that cells isolated from a Xenopus cybrid (Xenopus (Silurana) tropicalis haploid nucleus combined with Xenopus laevis egg cytoplasm) embryo are unable to proliferate and expand normally in vitro. We also provide evidence that the lack of nuclear donor species maternal poly(A)⁺ RNA-dependent factors in the recipient species egg may contribute to the developmental dead-end of distantly-related cybrid embryos. Overall, the data are consistent with the view that the development promoted by one species’ nucleus is dependent on the presence of maternally-derived, mRNA encoded, species-specific factors. These results also show that cybrid development can be improved without nuclear species mitochondria supplementation or replacement.

Keywords: :

• Xenopus laevis
• Xenopus tropicalis
• RNA transfer
• cell culture
• cybrid
• nucleocytoplasmic hybrid
• nucleocytoplasmic incompatibility

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

We would like to thank K. Miyamoto for his comments on the manuscript, and D.E. Simpson for his help. P.N. holds a postdoctoral fellowship form the Human Frontier Science Program and is a Junior Research Fellow of Wolfson College. R.P.H-S. is supported by a grant from the Medical Research Council. Work in the Gurdon laboratory is also supported by the Wellcome Trust.