Human activity, be it direct killing or destruction of habitat, is causing animals to go extinct at an alarming rate. Many have now got to a point where conservation and breeding efforts are the only path to keeping the species alive, and one of the efforts at the forefront of this is cloning.
To do so, however, is expensive and liable to failure. Genetic information is stored at incredibly low temperatures and should there be a power cut or the freezers are compromised in any way, this genetic material is destroyed. It also relies on the extraction of healthy sperm, which is no easy (or pleasant) task.
Now, new research has demonstrated the ability to clone mice using just somatic cells (not sperm or egg cells) that have been freeze-dried, a process significantly more suited to the task. The findings were outlined in a paper published in Nature.
“Here, we show that freeze-dried somatic cells can produce healthy, fertile clones, suggesting that this technique may be important for the establishment of alternative, cheaper, and safer liquid nitrogen-free biobanking solutions,” write the authors.
Current cloning techniques involve the removal of sperm or eggs – for example from the last Northern White Rhino – and long-term storage of sperm and embryos until they can be implanted into a female.
Teruhiko Wakayama and colleagues from the University of Yamanashi set out to expand on this by using freeze-dried somatic cells to provide the genetic material needed for cloning. Taking a sample of somatic cells from mice, the researchers subjected them to freeze-drying, in which the sample is frozen before the ice is removed. Doing so allows the sample to be frozen for up to nine months.
The cells do die in this process, but the researchers were able to perform somatic cell nuclear transfer and recover the nucleus, which contains all the necessary genetic information to create an early blastocyst. Soon, the researchers were able to create stable embryonic lines from the frozen samples.
Once implanted into females, the mice delivered healthy cloned litters, which were then mated further to prove they were able to reproduce.
The work is a major milestone in the pursuit of efficient cloning, but it is not without flaws. Freeze-drying results in more DNA damage compared to traditional methods, and somatic cell cloning has a slight reputation for birth defects. These are issues that will need to be ironed out before it becomes a viable method to save threatened species.