A study published in the journal Poultry Science indicates that a team from the University of Missouri, led by researcher Keiho Lee, has come close to developing chickens capable of producing proteins useful for medical applications inside eggs.
The idea of using chicken eggs as a source of pharmaceutical proteins dates back many years. For example, chicken eggs are used in the production of some flu vaccines, where the virus is cultured inside the egg and the resulting material is extracted to manufacture the vaccine. Antibodies, proteins that help the body fight infection, can also be extracted from eggs.
However, when attempting to introduce new genes into chicken DNA, scientists encountered a major problem: random insertion could cause the gene to stop functioning over time, a phenomenon known as epigenetic suppression. As a result, the desired protein is either not produced at all, or its production gradually declines across generations, hindering the development of stable and reliable breeds.
The researchers took a different approach, using CRISPR gene-editing technology to insert the gene into a specific location within the genome, linked to a gene known as GAPDH.
This gene plays a crucial role in metabolism, contributing to energy production from sugar, and it is constantly active because the cell cannot survive without it. Therefore, the researchers hypothesized that inserting the new gene into this location would ensure its continued activity.
"The GAPDH enzyme is essential for the energy production process, so it is constantly active. Based on this, we hypothesized that inserting the new gene into this location would maintain its constant activity."
To verify this, the scientists added a fluorescent marker to the inserted gene, so that the continued signal indicated continued activity.
The experiments showed encouraging results, as the fluorescent signal remained stable even after long periods of cell culture and division, indicating that the gene was not suppressed, which was not possible previously.
Although the experiments have so far been conducted only at the cellular level, and not on live birds, this approach represents a crucial step towards using chickens as a bioreactor to produce medical proteins in a stable and efficient manner.
