Prepare to make prehistoric monsters

Nature braces for the fun in the gene labs, as CRISPR paves the way to recreate bygone creatures:

The precise, efficient CRISPR–Cas9 gene-editing technique has already taken life-sciences labs by storm. Now it is sweeping through evo-devo, the field that seeks to explain the developmental changes underlying evolutionary adaptations.

Rather than simply infer what caused historic transitions, such as how fish developed limbs, scientists can check their hypotheses directly with CRISPR. The idea is simple: cut out the fish genes thought to be involved in making fins, and see whether the fish start to form something resembling feet.

Neil Shubin, a palaeontologist and developmental biologist at the University of Chicago in Illinois, has used gene-editing to examine how the tips of fish fins, or rays, were replaced by feet and digits in four-legged land vertebrates, or tetrapods.

While researchers know that ancient fish developed limbs – Shubin led the team that in 2004 discovered a 375-million-year-old fossil that seemed to catch that transition in the act – they also thought that the foot was an evolutionary novelty without an equivalent in fish, because rays and feet are made of different kinds of bone.

But Shubin says gene-editing has changed his mind. His team used CRISPR to engineer zebrafish lacking various combinations of the several hox13 genes they possess – genes that researchers already thought played an important role in laying down fin rays.

None of the mutants grew fully fledged feet, Shubin notes, but some possessed “fingery fins” made of the same kind of bone that builds fingers and toes in tetrapods. “As a palaeontologist I studied and trained thinking these are two different kinds of bones that are completely unrelated developmentally or evolutionarily,” says Shubin. “These results challenge that assumption.”

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