Researchers at the Oregon National Primate Research Center (ONPRC) have developed a new form of gene correction that will prevent the transmission of genetic disorders from mother to child, which may lead to a “revolutionary way” to treat inherited diseases. Dr. Shoukhrat Mitalipov and his 15-person lab are using a gene-editing technique that involves spindle transfer from the affected egg to the donor egg to address these heritable conditions.

The gene-editing technique described in this study, employed together with in vitro fertilization or IVF, could provide a new avenue for people with a known heritable disease-causing genetic mutation to eliminate the risk of passing the disease to their children. It could also increase the success of IVF by increasing the number of healthy embryos.

Dr. Mitalipov concedes his stem cell research has been controversial for some people, while many others see the human health benefits. “We produce stem cells using eggs. That’s always a controversial issue — where are you going to get eggs?” he said. “Even though egg donation to the reproductive field is a pretty standard procedure, [use of these eggs to generate] stem cells [has] always been questioned.”

While admitting there are concerns about how to ensure there’s no misuse of this scientific technology, “since these families clearly can benefit, I think it’s ethical we allow it,” Dr. Mitalipov said. “At the same time, if there are concerns that a clinic can use it for an unintended use, it can be regulated.”

However, he doesn’t think the technology will be misused. “There is no other nonmedical use for this technology,” he said. “It’s all toward the defective mitochondria and correcting it. In the U.K., they decided it case by case, at least at the beginning. Each family and IVF clinic has to submit an application. Something like that can be done here as well.”

Research from the California National Primate Research Center (CNPRC) is paving the way for future studies where the possibility of birthing gene-edited monkeys that can serve as models for new therapies is greatly increased. CNPRC scientists efficiently used CRISPR/Cas9 technology to modify the genes of rhesus macaque embryos.

Clustered Regularly-Interspaced Short Palindromic Repeats (CRISPR) is essentially a DNA segment that scientists can manipulate using a system known as CRISPR/Cas9 to edit the genes within organisms. CRISPR/Cas9 seeks and targets specific genes in organisms that are linked to diseases by utilizing a single strand of RNA as a guide to target specific genes for editing.

But the technology can also be imprecise – causing off-target effects to genes that were not intended to be targeted.

“One of the problems with the CRISPR/Cas9 approach is that you have to target the gene,” said Catherine VandeVoort, the core scientist at the CNPRC who collaborated with Keith Latham of Michigan State University and Dr. Daniel Bauer at Harvard Medical School for the study. Latham designed the CRISPR/CAS9 system used in the CNPRC project. “When you have a very short (gene) sequence that you are targeting, it may show up in different places, in another part of the DNA strand instead of where you intend. It can cause off-target effects.”

While rodent-based research models are good for studying diseases in the early stages of research, rodents differ from humans in many anatomical and physiological ways. Alternatively, nonhuman primates share many similarities to humans.

However, while the monkey research model is better for studying human disease, it is much costlier than rodent-based models. “In monkeys, we can’t afford any off-target effects and so we asked ourselves, ‘How can we make this more efficient?’” VandeVoort said.

To minimize the risk of the off-target effects, the study used a two-pronged approach to increase the efficiency of the CRISPR/Cas9 targeting.

The scientists successfully edited the genes of the monkey embryos with 85 percent efficiency. That study demonstrated the first time in the U.S. that this method could effectively be used in monkey embryos. VandeVoort said the embryos used in the study were not implanted in recipient female monkeys, but that a future study will transplant the embryos with a goal of creating a gene-edited monkey.

Reviewed August 2019

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Photo credit: Kathy West for the California National Primate Research Center

Only one individual in history has been cured of HIV. This person is known as “the Berlin patient,” named for the location where the renowned HIV-ridding procedure took place. Scientists at the Oregon National Primate Research Center (ONPRC) at OHSU are working to understand how a specific mutation in a gene may block HIV infection in the host. Using CRISPR technology, researchers are creating the same mutation and bone marrow transplantation performed on that patient to study how it might play a role in HIV infectivity.

Jon Hennebold, professor and chief, Division of Reproductive & Developmental Sciences, at ONPRC, said that Clustered Regularly-Interspaced Short Palindromic Repeats (CRISPR) genome-editing technology is responsible for these new insights. “You can’t fully study HIV in rodent models because it’s a primate-tropic virus,” he said. CRISPR is essentially a programmable molecular scissors that scientists can manipulate to edit the genes within organisms. CRISPR/Cas9 seeks and targets specific genes in organisms that are linked to diseases by utilizing a single strand of RNA as a guide to target specific genes for editing.

“This technique exploded in the scientific community about five years ago, so it’s relatively new,” Hennebold said. “Basically, CRISPR works by cutting the DNA in the target gene of interest, which in turn results in the creation of a mutation at that site when the cell repairs the gap in the gene,” Hennebold said. “It doesn’t do it randomly. It goes to a gene of interest and will cut the DNA at that point.” Further, “It was a huge advance from the standpoint of being able to modify genomes, so it could be used to modify many different organisms’ genomes. Previously, you were only able to do that in a few models. You could never apply the previous approaches to organisms other than mice.”

In addition to work with HIV, CRISPR is currently being used to help researchers understand conditions such as blindness, autism, and neurodegenerative diseases that are too complex to be studied in a rodent research model.