Ludwig-Maximilians-University (LMU) researchers believe that bovine embryos might be a better model for early human development than the mouse model. Because the mechanisms that underlie embryonic development in humans and cattle are very similar, the LMU team conducted a series of experiments to prove that bovine embryos would be more useful in understanding the earliest differentiation steps.
In the study published earlier this week in PNAS, the team used CRISPR-Cas9 in bovine embryos to delete OCT4, a gene that is known to play a key role in the regulation of pluripotency in mammalian embryos. In the mouse, loss of this gene results in the inability to generate cells that express a transcription factor called GATA6, while cells that express a marker of pluripotency named NANOG are not affected.
"In the bovine embryo, we found precisely the opposite effect," says Kilian Simmet, first author of the new study. "In this case, deletion of OCT4 inhibited the emergence of NANOG-expressing cells, while GATA6-expressing precursor cells developed normally."
A recently published paper had previously reported that human cells react to deletion of the same gene at the same stage in exactly the same way. According to the LMU authors, this is not the only case in which the regulatory circuits that control early embryonic development in humans show greater similarity to those employed in bovine embryos than to those that operate in the mouse system.