In the near future, we may talk about a “genome-edited person,” a phrase that I picked up at the Stem Cell Meeting on the Mesa last week. This idea was raised around experiments showing that it’s possible to engineer hematopoietic stem cells to resist HIV infection and essentially eradicate the virus from an infected individual (a mouse, in this case). These experiments spring from a bone marrow transplant that was done in an HIV-positive patient with acute myelogenous leukemia. The patient received bone marrow from a donor with a rare mutation that makes his T-cells resistant to HIV infection. So far, the patient is HIV- and cancer-free. Through genome editing, that same mutation could be introduced into a patient’s hematopoietic stem cells and reintroduced into their bone marrow.
Six years ago, Shinya Yamanaka discovered that just four transcription factors are needed to reprogram a cell whose fate was sealed into a stem cell. This year, he shared the Nobel Prize in Physiology or Medicine for his contribution to regenerative medicine. This technology is a like a science fiction dream come true. We can take someone’s skin cells or fat cells and turn them into any other cell in the body- neurons, blood, heart cells that beat. If people have a genetic disorder, this could be corrected through genome editing of stem cells we create from their body. This technology will change medicine, but it’s still in its infancy. This was a common theme of several talks: the science isn’t perfect.
More researchers are studying iPS cells at the same time that we are improving our ability to accurately sequence the entire genome and epigenome. Turns out, reprogramming introduces small changes, some of which may be significant. Gene activity changes because DNA methylation states change. Mutations are introduced by retrotransposons (sometimes called “jumping genes”), pieces of DNA that move around and can jump back into the genome at the wrong spot. So the DNA is the same, but not. A bump in the road that’s sure to be understood or overcome with time.
The California Institute for Regenerative Medicine (CIRM), which was founded by a state ballot measure to fund and direct stem cell research in the state, manages the larger picture of stem cell research and related translational medicine in the state. Part of their plan includes stem cell banking and developing Genomic Centers of Excellence. Together, these will help us better understand the genetics, genomics, and epigenetics of stem cells. For now, the field is aware that reprogramming has unintended consequences. It’s important that the public is aware of this, too. Patients and patient-advocates are very eager to see this technology available clinically, but scientists want to make sure that we’re not unintentionally hurting people by using it. Once the technology is sorted out, both stem cell therapy and genome editing may become commonplace.