December 17, 2014

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Chuck Bednar for redOrbit.com Your Universe Online

In a new proof of concept experiment, scientists have managed to edit the genome of sperm-producing adult stem cells, creating a break in the DNA strands of a mutant gene in mouse cells then repairing it by replacing flawed segments with corrected ones.

The process utilized in the study is known as homologous recombination, and researchers from Indiana University, Stanford University and the University of Texas used spermatogonial stem cells (the building blocks for the production of sperm and the only adult stem cells that contribute genetic information to the next generation) to demonstrate their technique.

By repairing flaws in these cells, the study authors said that experts could prevent mutations from being passed onto to future generations. The technique, which is detailed in a recent edition of the journal PLOS One, has tremendous potential for gene therapy as well as basic research.

We showed a way to introduce genetic material into spermatogonial stem cells that was greatly improved from what had been previously demonstrated, co-author Christina Dann, an associate scientist in the Indiana University (IU) Department of Chemistry, said in a statement Monday. This technique corrects the mutation, theoretically leaving no other mark on the genome.

Dann, lead author and former IU research associate Danielle Fanslow, and their colleagues had to overcome a number of difficulties in their research including the fact that spermatogonial stem cells are difficult to isolate, culture and work with. They were only able to create the correct conditions in which to maintain and propagate the cells following years worth of work by scientists at multiple laboratories.

A primary hurdle was to find a way to make specific, targeted modifications to the mutant mouse gene without the risk of disease caused by random introduction of genetic material, the university explained. The researchers used specially designed enzymes, called zinc finger nucleases and transcription activator-like effector nucleases, to create a double strand break in the DNA and bring about the repair of the gene.

Stem cells that were modified in the laboratory were then transplanted into the testes of sterile mice where they grew or colonized, indicating that the stem cells were viable. However, the researchers were unable to breed the mice, though they are do not know if it was abnormalities in the transplanted cells or the recipient testes led to the rodents failure to produce sperm.

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Scientists take step forward in "editing" human genetic mutations

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