Dr. Keith Latham, an associate professor of biochemistry at Temple University’s School of Medicine, is the lead author of a new cloning study set to be published in an upcoming issue of Developmental Biology.
The study sheds light about the early stages of development in cloned embryos. It proved that cloned embryos and normal embryos are not different with respect to some of the proteins regulating gene function.
Instead of the traditional unification of sperm and egg that creates a “normal” embryo, reproductive cloning uses nuclear material from a somatic, or body cell, and unites it with an oocyte, an egg in early cellular stage. Because of the introduction of somatic cells to an embryonic cell environment, some reprogramming has to occur.
“By reprogramming, what we mean is you have to turn off the gene expression program of the donor cell that you’re getting your nucleus from and you have to turn on the gene expression program that a normal embryo would have,” Latham said.
“This reprogramming process doesn’t happen right away. It gets started in the early egg, but it is clear that a lot of this reprogramming happens in the next four or five days or week or so of life.” Latham said.
This observation, supported by Latham’s data, is contrary to the idea held by many in the scientific community that reprogramming happens only in the early egg.
“As part of trying to understand why cloning doesn’t work any better than it does, we have to sort of go back to the beginning and figure out what things are going right and what things aren’t going right,” Latham said.
Latham’s study showed that in 100 percent of the cloned embyros, the oocyte behaved as its counterpart in normal embryos. When it was necessary, the oocyte was able to switch the gene regulating proteins from the somatic cell and replace them with its own embryonic gene regulating proteins.
As the cloned embryo aged and it became necessary to switch back to the somatic cell gene proteins, the oocyte was also able to do this with success.
Latham said the problems with maintaining a cloned embryo until birth can be attributed to the media in which the cells are stored. Scientists are not certain what mix of embryonic cell culture media and somatic cell culture media is needed.
“[The cells] have an identity crisis. They’re not embryonic cells and they’re not somatic cells. They’re something in between because you’ve partially reprogrammed them, so we’ve created this new identity,” Latham said.
If scientists can find out what culture system the embryos need to remain healthy, it is possible that cloning would be more successful. If the cloning process can be improved, applications ranging from preserving and propagating endangered species to making viable pharmaceutical compounds from cloned animals’ milk could be available. Latham plans to continue his work in the field.
The study was conducted through collaboration with researchers at the University of Utah and Peregrine Pharmaceuticals and is the latest installment in a series of studies funded by two National Institute of Health grants.
Tulin Ozturk can be reached at firstname.lastname@example.org.