Insulin From Microbes, Calm Dogs From Careful Breeding

A Checkup at Lakeview Children's Hospital

1Tomasz Adeyemi is thirteen and has type 1 diabetes, which means his pancreas makes very little insulin. Insulin is a protein that helps cells take in sugar from the blood. Several times a day Tomasz gives himself insulin with a pen, and every three months he visits Dr. Rania Castellanos at the diabetes clinic of Lakeview Children's Hospital. At his last checkup he asked her where his insulin comes from.

2Dr. Castellanos explained that before the 1980s, insulin for patients was collected from the pancreases of pigs and cattle. Pig insulin differs from human insulin by one of its building blocks, and cattle insulin differs by three, and some patients had allergic reactions to it. Today most insulin is made by genetically engineered bacteria or yeast. Scientists put a copy of the human insulin gene into the microbes' DNA. The microbes multiply in huge steel tanks, and each new cell carries the gene and builds human insulin, which is then purified. Human insulin made by bacteria was approved for patients in the United States in 1982.

3After the checkup, a pharmacist showed Tomasz other medicines in the hospital pharmacy that are made by engineered cells (Table 1). In each case, people added a gene that the cells did not have before.

4On the way out, Tomasz met Juniper, one of the hospital's facility dogs, who keeps young patients company during tests. Juniper came from a nonprofit program that breeds and trains dogs for hospitals. For each dog, trainers score calmness from 0 to 10 during the same set of tests with loud noises, crowds and slippery floors. The program chooses only calm, healthy dogs to be parents. Its training methods have changed little since 2008. Figure 1 compares parents' scores with their pups' scores for seven litters, and Table 2 shows the share of pups that finished training and became working dogs.

5Dr. Castellanos added one more example. For a few rare inherited diseases, such as one kind of inherited blindness, doctors can now place a working copy of a gene into a patient's cells. This is called gene therapy. It changes only the cells that receive the gene, such as cells in the eye, and not the cells that make eggs or sperm.