Current Trends in Gene Manipulation

Overview

Biotechnology involves the alteration or use of cells or molecules for specific applications. The biotechnology that relates to the manipulation of genetic material is called genetic engineering. The result of combining the genetic material of one species with another is called recombinant DNA.

Recombinant DNA technology had its roots in 1975, when 140 microbiologists met to discuss the possibilities of a new type of experiment. Technology had developed the tools for recombining genes from different species. Called restriction enzymes, these tools cut pieces of DNA so that other pieces can be added. These restriction enzymes allow scientists to recombine the genes of different species. The process is also known as genetic engineering. A transgenic organism develops from a gamete that has been altered by the recombination of genes. Transgenic animals are used to "pharm" (produce) useful human proteins or to model human diseases. Cloning is accomplished by inserting material from a somatic, or body, cell into a germ cell (egg).

With the development of procedures that manipulate living things and combine the traits of uniquely different species, ethical questions arise. Fear of the unknown also comes to play a part. Legal and political challenges have emerged from many corners.

Background

Biotechnology in a broad sense has been around since ancient times. Adding yeast to make bread or wine, using pectin to make jelly, or using enzymes to remove stains from dirty clothes are all examples of using biological materials. Molecular biology, however, has its roots in 1938, when Warren Weaver, director of the Rockefeller Foundation, spoke to his trustees about a new branch of science called "molecular biology" that was beginning to uncover the secrets of the cell. This moment was the first time the term "molecular biology" appeared in print. The term was again used in 1950, when a British x-ray crystallographer used it in a Harvey lecture. "Molecular biology" was off and running.

Impact

In February 1975 Asilomar, a conference center in California, was the site of a meeting of 140 molecular biologists. Researchers had found a simple way to combine the traits of two species and were concerned about where the new field of biotechnology was heading. They discussed safety implications and restrictions that should be in place to prevent the escape of a recombinant organism from the laboratory. Guidelines were also drawn up for laboratory features, such as hoods, and a general tightening of procedures. When the group met ten years later in 1985, they were amazed that the technology had proved safer than predicted and had moved from the research lab to industry much faster than they could have imagined.

In 1977 the age of biotechnology was born. That year a manmade gene was used to manufacture a human protein in a bacterium. Herbert Boyer at the University of California, San Francisco inserted a synthetic version of the human insulin gene into the bacterium Escherichia coli.

Manipulating the DNA molecule required biochemical scissors called restriction enzymes. Scientists use these enzymes to cut a gene from its normal location, insert it into a circular piece of DNA (called a plasmid), then transfer these circles into the cells of another species. The value of plasmids is that they can pass from one cell to another. For example, a human sequence called cDNA can be inserted into the plasmid ring, which is then inserted into a microbe's DNA. Plasmids thus are used as vectors to transfer genes between organisms. Bacterial cells divide approximately every 20 seconds, so millions of copies, or clones, containing the human gene can rapidly result. This procedure allows a genome to be manipulated more readily than does the natural breeding process in addition to being able to combine the traits of species. The potential applications of genetic engineering in such fields as food technology, agriculture, forensics, and medicine are staggering.

With such a technology, there are naturally legal and ethical conflicts. In 1980 the U.S. Supreme Court ruled that genetically altered life forms can be patented. Although the decision specifically allowed the Exxon oil company to patent an oil-eating bacteria, the door was opened for commercial genetic engineering. In 1981 Congress held a series of hearings on intellectual property and patent rights.

In 1990 the Human Genome Project was begun to map all human genes, and the first gene therapy trial was carried out on a four-year-old girl with a genetic disorder, called ADA deficiency. While the therapy worked, it set off a firestorm of ethical debate that exploded in the media. Michael Crichton's novel Jurassic Park described a theme park where bioengineered dinosaurs roam and frightening results occur when the experiment goes awry. The book's dramatization into a film fanned the flames even more. In 1995 a coalition of religious groups sought to overturn current laws allowing the patenting of genes used for medical work and research. Jeremy Rifkin, an outspoken critic of biotechnology, led a media charge. A survey taken in 1996 showed most people to be suspicious of gene therapy.

The prospects of genetic testing also led to ethical questions. The U.S. Defense Department created a kind of "DNA dogtag" file of genetic fingerprints that could help identify the bodily remains of military personnel. These "prints" would be stored in a repository. The question emerged as to who would have access to the DNA repository—for example, the police or insurance companies that might use the information to refuse coverage if a person carried a gene for a debilitating disease. The questions over the potential benefit and damage of such a program have still not been answered.

The area of genetic screening has raised many questions. Surveys have revealed that the public knows little about genetic testing and even less about gene therapy. Even more frightening is that people who knew nothing about the subject approved of using genetic engineering to improve their children's physical appearance or intelligence. Television programs promoting "perfect people" also added to the confusion.

The year 1997 was rife with discovery and controversy. That year, the public first heard about cloned sheep and monkeys, babies from frozen eggs, headless frog embryos, a 63-year-old mother, and sperm taken from dead men. Debates over bioethics grew but in no way could keep up with the pace of science.

When Dolly, the first cloned sheep, nuzzled her way into headlines in 1997, Ian Wilmut of the Roslin Institute in Edinburgh, Scotland, became a media sensation. He and his staff had cloned Dolly from a cell derived from the mammary gland of a six-year-old sheep. The procedure in theory was simple. An unfertilized egg (oocyte) was removed from the ovary of an adult ewe. The nucleus was replaced with the nucleus of a cell from an adult sheep's mammary gland, and then the egg was implanted into another ewe.

In July the same researchers cloned Polly, the first sheep bearing human genes. Polly could be good news for hemophiliacs, who rely on expensive protein therapy for their condition. On March 4 of the same year, a group of researchers in Oregon cloned two rhesus monkeys from early stage embryos, using nuclear transfer methods. Donald Wolf, the senior scientist on the project, said such animals could be useful in the design of studies for cancer and AIDS.

This cloning research, however, set off alarm bells in Washington, D.C., as visions of cloning humans came closer to reality. The media unleashed a furor centered on pictures of cloned armies, tanks of living organisms for transplantation, and bringing back the dead. President Clinton banned human cloning and told the National Bioethics Commission to review the ethical and legal implications of cloning. In addition, Congress submitted bills banning human cloning and revived old bills on genetic screening, or "snooping."

The research that created Dolly was not new and had been in the making for many years. Nuclear transfer in frogs began in 1950. In 1986 a team of scientists from the Medical College of Pennsylvania transferred nuclei from red blood cells (unlike humans, frogs have nuclei in their red blood cells) to enucleated frog eggs. ("Enucleated" refers to a cell whose nucleus has been taken out.) The clones, however, did not live past the tadpole stage.

Nancy, Ethyl, and Herman were transgenic pioneers. Nancy is a sheep that produces human alpha-1-trypsin (ATT), a material necessary to inflate lungs properly. To engineer Nancy, scientists gave a ewe a drug to produce mature eggs then artificially inseminated her. The fertilized eggs were washed out and micro-injected with copies of the ATT gene. These eggs were then inserted into a surrogate ewe. While the process may sound simple, it was not. Many genes did not go into the correct part of the host's genome, where they were to be expressed. Of 152 implanted eggs, only Nancy had the proper transgene. Ethyl, from Scotland, was engineered to make factor VIII, a protein necessary for blood clotting. At Virginia Tech, genetically engineered piglets were developed to produce the factor in their milk, so that 300 to 600 milking sows could meet the needs of the world's hemophiliacs. Herman, a transgenic dairy calf, has a gene that codes for lactoferon, to be added to infant formula to prevent infection. Dolly was special because she was cloned from the cell of an adult ewe. In 1998 Japanese scientists cloned eight identical calves using cells from one adult.

By the end of the twentieth century, discoveries had grown so numerous they could not be counted. Techniques for analysis and study are likewise becoming sophisticated and complex. For example, a technique may combine PCR, DNA chips, and computer programming to search the genome. Also, high throughput technology allows a multitude of analyses in a short period of time and is valuable in drug discovery. A December 1999 release from Ian Dunham of Cambridge University stated that his team had cloned the genetic sequence for all of chromosome 22, the smallest of the 23 human chromosomes. Also in December, Clyde Hutchison of the University of North Carolina published his discovery of the minimal number of genes required to produce a living organism. The Human Genome Project, moreover, is on time and under budget. A target year for completion was set at 2003. As genetic discoveries increase, however, so will the ethical and legal challenges.

EVELYN B. KELLY