But to know if he had those male parts because of Crispr would require peering into Cosmo’s DNA. The team drew a few vials of blood from the calf’s neck, and Owen raced it over to the lab and got it into a fridge to start a 16-hour cooldown. He went home, had a few beers to settle his impatient anxiety, and set his alarm for 6:30 the next morning. At 5:00 am, he shot awake and hurried back to the lab while it was still dark. Owen extracted DNA from the calf’s blood and used a technique called PCR gel electrophoresis to look for the presence of the extra SRY and GFP genes. About fours hours later, when the band showed up right where expected, a shock of elation shot through his body. “Holy shit, you really did this!” he thought to himself.
Owen looked around, taking in the moment among the silent instruments. Because of the pandemic, only one person was allowed in the lab at a time; his colleagues were all sheltering at home. So he snapped a pic of the gel and emailed the team.
In her bedroom/home-office, Van Eenennaam clicked on the email, ready for it to be more bad news. Instead, triumph washed over her. “Yessss!” she recalls exclaiming, fists pumping the air.
The gel result wasn’t a total home run. It revealed that Cosmo was XY, meaning he had inherited a copy of SRY from his biological bull-dad, as well as the SRY gene that Owen had Crispr’d onto his 17th chromosome. Even without the editing, he was always going to be a male. But the knock-in had worked, using Crispr in a bovine embryo for the first time ever. “Getting that result was really cool,” says Van Eenennaam. “It was actually one of the best science days ever.”
But there was something else that had shown up in the first, quick scan of Cosmo’s DNA. That was a piece of genetic code that didn’t belong to a cow or a jellyfish, but to a bacteria. To insert such a large gene—SRY is a few thousand DNA letters long—into the single-celled embryo that would become Cosmo, Owen had had to deliver it into the cell the only way scientists knew how: inside a circular piece of bacterial DNA called a plasmid. After Crispr had made its cuts, Cosmo’s repair enzymes had grabbed the plasmid along with the SRY gene and pasted the whole thing into his genome.
This kind of mistake has happened before. A similar plasmid was discovered last year in a pair of genetically dehorned bulls created by Minnesota-based biotech company Recombinetics using the clone-an-edited-cell-into-an-egg approach. Van Eenennaam secured funding from the USDA to study Recombinetics’ bulls and their descendants to see if the genetic alteration was inherited as intended. The plasmid was uncovered by an FDA scientist analyzing DNA sequence data from some of their offspring, after Van Eenennaam petitioned the agency for a regulatory exemption so the animals, produced at UC Davis, could be slaughtered and sold locally.
Recombinetics’ scientists had never bothered to look for the presence of plasmid. While such bacterial DNA has not been shown to produce any ill effects on the animals or their meat, in many countries it does redefine them as GMOs, subjecting them to tighter regulatory scrutiny. The revelation scuttled the company’s plan to raise a founder herd in Brazil from one of the bulls’ semen. It was a huge blow to the small but growing livestock editing industry.
But it succeeded in raising the awareness of such potential problems. So Van Eenennaam’s team had planned ahead of time to do a deep dive into Cosmo’s DNA. That, too, got complicated by the pandemic. UC Davis’s sequencing core was shut down. So the team sent bits of Cosmo’s blood, tissue, and placenta to two different companies to piece together what he was really made of. What they got back was even weirder than they’d expected.
