Huntington's gene: so near, yet so far

Article Abstract:

Research on Huntington's disease received a tremendous boost in 1983 when Jim Gusella discovered that the gene which causes it is located near the tip of one end of chromosome number 4. Chromosomes contain the genetic material, or genes, that are passed on between generations, and millions of genes exist in the nuclei of an individual's cells. Localization of the Huntington's disease gene occurred sooner than scientists had predicted and generated intense enthusiasm for a collaborative effort among workers. At the urging and support of Drs. Nancy Wexler and Allan Tobin of the Hereditary Disease Foundation, the Hereditary Disease Foundation Huntington's Disease Collaborative Research Group was formed, comprised of six major research groups. Scientists who are part of the collaboration receive grants from the Foundation to support postdoctoral scholars, and, in exchange, share unpublished, often preliminary, results with each other before making them public. If a discovery is made, the entire group will share the credit. Their scientific strategy uses a type of DNA marker called a restriction fragment length polymorphism (RFLP). This refers to a location along the chromosome where the DNA sequence varies among individuals. If a particular RFLP appears consistently on the same chromosome from people in the same family with an inherited disease, it is likely that that fragment of genetic material is linked to the disease. Two large families with Huntington's Disease, one in Venezuela, one in the Midwest, contributed blood samples which led to the original finding. Chromosomal markers from other family members, however, indicated that the gene lies on a different segment of the chromosome from what was originally thought. Results from different laboratories have been confusing and contradictory, with that region of chromosome 14 proving hard to visualize. Partly to resolve this problem, the Group has now divided up the chromosome into territories, with different laboratories focusing on different regions. Discoveries which initially appeared promising have so far failed to yield major insights. But members of the collaboration, which has displayed a blend of cooperative zeal and scientific rigor unusual in the competitive atmosphere of today's research world, maintain great optimism that this joint approach will be the one that successfully isolates the Huntington's disease gene. (Consumer Summary produced by Reliance Medical Information, Inc.)

Management, Genetic aspects, Biological research, Huntington's chorea, Huntington's disease, Gusella, James, Wexler, Nancy S., Tobin, Allan

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Whatever happened to the genetic map?

Article Abstract:

Scientists are trying to map the sequence of the genes in the human genome, which is the entire set of man's genetic codes. A partial map was completed in 1987, which allowed the identification of genes that cause a number of inherited diseases such as cystic fibrosis, Duchenne muscular dystrophy, and Huntington's disease. The project is a major undertaking, originally thought to take three to five years and cost 10 to 15 million dollars a year. It is now realized, three years into the project, that the scientists cannot achieve their goal unless there is a change in policy. It appears that scientists are not working on the map at the scale that was envisioned. Instead, scientists are more interested in looking for the genes that cause disease, which the map was supposed to make easier to find. The map is supposed to identify markers, or segments of DNA (deoxyribose nucleic acid) very close to one another, to allow easy identification of genes in between the markers. This has proven to be too difficult. Now scientists are aiming for markers to be two to five times further apart than originally planned. This distance will make it more difficult to isolate genes of interest. The National Institutes of Health genome center is considering ways to get scientists to work on the project, such as contracting grant money for the work. (Consumer Summary produced by Reliance Medical Information, Inc.)

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The genetic map is back on track after delays

Article Abstract:

The first goal of the National Institutes of Health's (NIH) Human Genome Project was to make a fine-resolution genetic map of all the chromosomes, primarily because it would be a very valuable tool for tracking down genes specifically involved in disease. This task was delayed because of internal bureaucratic problems at NIH. A new strategy to make an 'index' map of special markers spanning all the chromosomes was agreed upon last week, and the project's tasks were divided. Each major research group involved in the project agreed to be responsible for identifying index markers on specific chromosomes, and for tagging a site on each marker for quick identification on the final gene map. These markers are actually short detectable pieces of deoxyribonucleic acid (DNA) along each chromosome, which, once identified, will enable any gene to be located. The final map will have markers at smaller intervals than the index map, but the index map will be used as the skeletal structure on which to fill in these final markers. (Consumer Summary produced by Reliance Medical Information, Inc.)

Reports, Genetic research, Human genome

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