Gene editing tool holds great promise

Q: My son said he learned in school about a powerful new technique for editing genes that could possibly cure diseases. It also sounds a little scary. Can you tell me more?

A: Your son probably is talking about a technique called CRISPR. This technique already is having a great impact on biological research, and it may someday help cure some human diseases.

Many diseases are caused by defects in how genes are built. This, in turn, can cause a defect in how the protein made by the gene is built. A good example is the first disease in which a genetic defect was identified: sickle cell anemia. The disease brings terrible pain and damages organs. It can even cause strokes to occur in children. Without treatment, it can be fatal.

In sickle cell anemia, the defect is in the gene that makes a protein called globin. Globin is inside red blood cells and carries oxygen to all parts of the body. The CRISPR technique allows a scientist to find that defect in the gene and correct it.

So will CRISPR cure sickle cell anemia?

Maybe.

But it won't be simple. Editing genes in cells in a laboratory dish is one thing. It's quite another matter to edit genes in the cells of a living animal or human. Diseases typically affect certain cells in certain organs. So, to correct those diseases requires targeting just those genes, in just those cells and organs, deep within the body. That is a real challenge.

Nevertheless, some success already is being reported in editing genes inside living animals. For example, the technique was recently used to edit a gene in a mouse's liver that affects the level of cholesterol in the blood. CRISPR achieved a prompt and marked reduction in cholesterol - without any apparent ill effects.

Another challenge: Most diseases are caused by defects in multiple genes, not just one, as in sickle cell anemia. However, the technique already has been modified to edit multiple genes simultaneously.

The CRISPR technology has the potential to affect our lives beyond curing diseases. Experiments are underway to see if it can reduce the number of disease-carrying insects, or to grow hardier crops.

Any powerful new technology can, as you say, also be scary. A panel of distinguished scientists recently urged the world's scientific community to refrain from using CRISPR to edit genes in human eggs or sperm until more is known about whether there may be potentially harmful results.

There are two lessons in the story of CRISPR. First, we humans are smart enough to make breakthroughs like CRISPR, but not smart enough to know from where those breakthroughs will come. CRISPR was discovered by scientists pursuing an arcane question: how bacteria defend themselves from viruses. The scientists were not trying to invent a technique for editing human genes.

The second lesson: It is wise for society to invest in curious people who try to understand how living things work. That's what leads to breakthroughs.

• Dr. Anthony Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.