For anyone wondering how, quoting ‘
The Science Behind the Return of the Dire Wolf’, with added information in brackets:
“Colossal says its dire wolf work had key differences (to tradition cloning).
Scientists first analysed the genome of the dire wolves contained in the ancient tooth and skull (from a 13,000 year old tooth and a 72,000 year old skull). Comparing those genomes to that of the grey wolf—the dire wolf’s closest living relative (which share 99.5% of their DNA with, despite the last time grey wolves and dire wolves sharing a common ancestor being about 5.7 million years ago)—
they identified 20 differences in 14 genes that account for the dire wolf’s distinguishing characteristics, including its greater size, white coat, wider head, larger teeth, more powerful shoulders, more-muscular legs, and characteristic vocalisations, especially howling and whining.
Next, they harvested endothelial progenitor cells (EPCs), which form the lining of blood vessels, from the bloodstreams of living grey wolves—a less invasive procedure than taking a tissue sample—and edited the 14 genes in their nuclei to express those 20 dire wolf traits. This is trickier than it seems, since genes often have multiple effects, not all of them good.
For example, as the company explains in its press release, the dire wolf has three genes that code for its light coat, but in grey wolves they can lead to deafness and blindness. The Colossal team thus engineered two other genes that shut down black and red pigmentation, leading to the dire wolf’s characteristic light color without causing any harm in the edited grey wolf genome.
Once this was finished, the edited nuclei were next extracted from the cells and inserted into denucleated grey wolf ova.
The ova were left to grow into embryos and 45 were transferred into the wombs of two domestic hound mixes. One embryo in each surrogate mother took hold, and after 65 days of gestation, Rolulus and Remus (the six-month-old males). A few months later, the procedure was repeated with a third surrogate who ultimately gave birth to Khaleesi (the two-month-old female). All three births were conducted by scheduled cesarean section to minimize the chances of injury during delivery. No surrogate dogs had a miscarriage or stillbirth during the process.”
EDIT: Just to clarify, this is the
phenotype of a dire wolf, although truly the pups are grey wolves with seventeen or eighteen changes in their DNA.