When stem cells transform rabbits into effective animal models

Obtaining germline chimeras requires pluripotent stem cells (iPSCs), i.e. cells capable of producing all types of cells in the body, including reproductive cells (eggs and sperm). The advantage of these stem cells is that they can pass on their DNA to offspring. The model is well established in mice and rats, but it is not suitable for studying all human diseases. Teams from USC SBRI and UMR BREED have just taken a decisive step forward by achieving this result for the first time in a non-rodent animal, in this case the rabbit, opening up new prospects, particularly for the study of complex human diseases.

To achieve this, the researchers used three genes (KLF2, ERAS and PRMT6), which they identified as key factors in pluripotency. These three genes were used to reprogram rabbit iPSCs to a ‘naive’ state (a very early stage of development), which is more conducive than the ‘primed’ state (a later stage) to embryonic integration and tissue colonisation during development.

Injected into embryos at an early stage of development, the reprogrammed iPSCs (and labelled with the GFP gene, a green fluorescent protein) gradually colonised all tissues, including the reproductive organs. They contributed up to 100% to the formation of certain organs, including the heart, pancreas, skin and ovaries. The rabbits born from these embryos developed normally and, once they reached adulthood, two healthy female rabbits were able to pass on the modified DNA from the iPSCs to their offspring, demonstrating functional germline chimerism.

Researchers attribute this success to the choice of three key genes that play a decisive role in maintaining the ‘naive’ state of stem cells: KLF2 controls the expression of genes involved in the cell cycle, ERAS reinforces signalling that promotes the naive nature of cells, and PRMT6 modulates the epigenome to stabilise this state.  Together, they have thus removed the barrier that had previously prevented iPSCs from contributing to germ cells in rabbits.

This work has enabled a major breakthrough in creating germline chimeras in rabbits using an effective trio of genes (KLF2, ERAS, PRMT6). This greatly expands the prospects for creating animal models that are better suited than rodents for studying complex human diseases.