Page 37 - Breeding Edge ebook

For anyone on a transplant waiting list – and there are plenty – that’s welcome news. In the U.S.
today, more than 116,000 people are waiting for an organ transplant, according
to orgondonor.gov. Roughly 20 people per day die waiting.

Recombinetics is working on pig embryos that had been injected with human stem cells to begin
growing organs containing human cells, creating what’s known as a chimera, scientists reported in
January 2017. Chimeras have cells from two different types of organisms.

Researchers hope they will eventually be able to grow new human body parts for transplantation – a
transplant organ that’s uniquely made to match a human’s DNA. But for now, they need to figure out
how to get more human cells to survive inside of their pig, cow or sheep host.

SAB Biotherapeutics, on the other hand, uses cattle as its living factory of antibodies to help people
fight disease, in part because cattle are big, thus turn out big volumes of antibodies. Its genetically
designed cattle, Tc Bovine, produce a menu of antibodies the same way that other cattle or people make
antibodies, except they produce human antibodies instead of cattle ones. Its antibodies can be aimed at
“prevention and treatment of diseases from Ebola to cancer, and diabetes to influenza,” the company
says on its website.

Chicken eggs, too, have been harnessed as factories for biomedical research and health care. Trouble is,
a lot of children are allergic to eggs. So, they can’t get some immunization shots, since many major
vaccines are cultured in chicken eggs.

Australian researchers report, however, that they have altered an egg-white gene largely
responsible for the allergy, making the egg hypoallergenic. That suggests hypoallergenic egg-based
vaccines may be on the way.

The dynamics of editing animal genomes changes when the editing is done on wild species or when
unlimited, worldwide adoption of such an edit is contemplated. As with the Dunham goal of raising
sterile catfish, breeders think about the need for a brake pedal, so that a dominant and potentially
harmful trait, doesn’t enforce itself around the world.

Breeders think about brake pedals

Intrexon, for example, developed male Oxitec mosquitos that pass on to offspring a self-limiting trait
wherein the offspring don’t live to adulthood. As a result, the local mosquito population declines.

Those mosquitoes have been spread in recent years in Brazil, Panama, the Cayman Islands and Florida
in efforts to control the mosquito population that carry Zika, dengue and other dangerous viruses. A
Zika virus infection during pregnancy created alarm for thousands of women when it was
identified as a cause of congenital brain abnormalities.

On the other hand, consider what may be the biggest weapon for controlling organisms in the wild – a
gene drive. The genetic tweak employed by Intrexon means female mosquitoes will have dead-end
offspring when mating with the mutant males; not when they mate with other males.

The concept is simple. Just ensure the gene or genes for adding or blocking a trait are on both
chromosomes – thus, a double dominant modification that will be carried to practically all offspring. For
example, a gene drive could single out a species, like pesky rats, to potentially eliminate.

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