Doran's quest to modify allergens in chicken eggs requires delicate control.
The trick is to finely adjust a genetic sequence in a way that will stop the protein from triggering an immune reaction in people, but still allow it to perform its normal role in embryonic develop ment.
CRISPR has made such precise edits possible for the first time.
"CRISPR has been the saviour for trying to tackle allergens, he Mark Tizard, a molecular biologist at CSIRO who works with Doran on chickens. Using the technique in birds still presents problems.
Mammals can be induced to produc xtra eggs, which can then be removed, edited fertilized and replaced.
But in birds, the fertilized egg binds closely to the yolk and removing it would destroy the embryo.
And because eggs are difficult to access while still inside the hen, CRISPR componenents cannot be directly injected into the egg itself. into. By the time the egg is laid, development has proceeded too far for gene editing to affect the chick's future generations. Unlike in many animals, chicken PGCs spend time in the blood-stream during development.
Researchers can therefore remove PGCs edit them in the lab and then return them to the developing bird.
The CSIRO team has even developed a method to insert CRISPR compo-nents directly into the bloodstream so that they can edit pgcs there.The researchers also plan to produce chickens with components required for CRISPR integrated directly into their genomes what they call CRISPi chickens. his would make it even easier to edit chicken DNA, which could be a boon for farmaceuticals drugs created using domesticated anima. Regulators have shown a willingness to consider such drugs. in 2006, the European Union approved a goat that produces an anti-clotting protein in its milk. It was subsequently approved by the Us Food and Drug Administration, in 2009. And in 2015, both agen cies-cies approved a transgenic chicken whose eggs contain a drug for cholesterol diseases.