By the time Crystal Preston was 3½ months old, she could not suck formula from her bottle. For the next year, she had to be fed through a tube in her nose, and even now, at 7½ years of age, the 38-lb. Ottawa-area girl has to take food supple-
ments every night through a tube in her stomach. She suffers from myotonic dystrophy, one of the most common forms of muscular dystrophy, a degenerative disease that attacks the nerves and muscles. As a result, she has been slow in learning to speak and in developing motor skills.
But last week, Roger and Linda Preston, who live with their daughter in Edwards,
Ont., welcomed reports that a group of medical researchers, including a Canadian team led by Ottawa’s Robert Korneluk, had identified the genetic defect that causes myotonic dystrophy. Declared Roger Preston, a 37year-old electrician who carries the defective gene, but who does not suffer from the disease himself: “It’s a major breakthrough.”
Medical experts said that by pinpointing the defective gene responsible for the disease, the researchers have
opened the way to improved treatment—and even a cure—in the future. Writing in the respected British scientific journal Nature, researchers from Britain, Canada, the Netherlands and the United States reported that the defect which causes myotonic dystrophy is located on the 19th chromosome. (Each cell of the human body contains 23 pairs of chromosomes, which determine the genetic blueprint of every individual.)
After spending five years immersed in research, Korneluk, who is director of the molecular genetics laboratory at the Children’s Hospital of Eastern Ontario in Ottawa, said that he was pleased by the amount of publicity the breakthrough generated.
Said Korneluk, 41: “It was exciting to find the mutation, but the actual impact of it all didn’t really strike me until I saw it on TV.”
One immediate result of the discovery is that in the future, a simple blood test can be used to determine who carries the defective gene and, as a result, risks passing it on to their children. Pregnant women will also be able to find out whether their fetus has inherited the disease.
“Now, we’ll be able to test to see who has it,” said Rick Ashbee, a spokesman for the Toronto-based Muscular Dystrophy Association of Canada, which provided some of the funding for the research. He added: “From there, we can work on how to solve it.”
Myotonic dystrophy can manifest itself at any age and affects about one in every 8,000 people worldwide. In the Saguenay region
north of Quebec City, the disease occurs in approximately one in every 500 people—the result of the gene defect’s occurrence in an area first settled by a relatively small number of families, many of whose descendants still live there. Currently, there is no cure for the disease, which may be transmitted through either parent. In one form, myotonic dystrophy usually appears in adolescence or early adulthood. Also known
as Steinert’s disease, it causes wasting and weakness of the muscles, especially in the face, neck, arms and legs. In addition, the disease causes myotonia, which makes it difficult to relax contracted muscles. Researchers have discovered that myotonic dystrophy, unlike most genetic diseases, gets worse as it progresses from generation to generation.
Finding solutions to the many problems raised by the findings is a search that Korneluk is well equipped to carry out. After graduating from high school in Sault Ste. Marie, Ont., he studied zoology at the University of Toronto, earning a bachelor of science degree and later a PhD. In 1982, he joined the genetics department at Toronto’s Hospital for Sick Children on a postdoctoral fellowship. “It was like going to another world,” said Korneluk, who noted that the science of genetic engineering was still in its infancy. He worked on identifying and cloning, or copying, genes that caused such diseases as Tay-Sachs, a genetic disorder common among Ashkenazi Jews. Said Korneluk: “I learned a lot about how to hunt down a gene.”
Six years ago, Korneluk moved to his current job, but he recalls feeling that he was leaving Toronto for an uncertain future—and worse winters. His initial task in Ottawa was, in fact, to develop a research program for myotonic dystrophy. Because of the nearby Saguenay population, Korneluk’s team eventually amassed the largest record of families and individuals with myotonic dystrophy in the world. In 1988, Korneluk and his 15-member team of researchers linked up with the six other international teams of scientists in the field and devoted four years to searching through the millions of items of genetic information that make up the 19th chromosome. Said Korneluk: “It’s like that magic trick with the handkerchiefs—you pull out one gene and then the next gene and so on.” He added that the Dutch team was approaching the middle of the chromosome from the opposite direction and, along the way, both teams were identifying each gene that they found. Together with the other two teams, scientists discovered the defect—an expanded region on the gene that causes the disease.
Korneluk says that he now plans to tum his attention to the clinical and biological mysteries of how the disease develops—and what can be done to prevent it. Said Korneluk: “We can begin to answer how the disease comes into play and design rational approaches to treating it. This information will lead to a cure some day.”
Korneluk plans to attend a series of conferences abroad involving myotonic dystrophy. That means leaving his wife, Margo, 41, his daughter, Yolanda, 21, and son Paul, 10—as well as his twice-weekly hockey games with hospital staff members. “I don’t spend all my time in my lab,” he said. “But my lab is really my hobby.” Now, the long hours of work by Korneluk and his fellow researchers have paid off with the development of a wider knowledge for the Prestons and thousands of other victims of a dreaded disease.
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