Repeats in the Book of Life may affect disease

A research team from Cold Spring Harbour Laboratory has found a surprising degree of variation in repeated regions of the human genome. The discovery was made whilst researchers were looking for repeated DNA that might cause cancer, using a new laboratory technique. The results, published this week in the journal Science, are a significant step in our understanding of the human genome: the variation in the repeated regions are likely to play a role in development and disease.

Even before the human genome was sequenced, it was known that sections of DNA are repeated. The research team has found 76 sections where the number of copies varies between individuals: one person may have five copies, another may have ten. The researchers also found that 70 genes lie within these 76 sections; the number of copies of these genes will vary with the number of copies of the section. As these genes include those involved in Cohen syndrome, neurological development, leukaemia, breast cancer, and regulation of food intake and body weight, it could be that increased copy number is responsible, at least in part, for causing the related diseases.

The technique that made the research possible was developed at Cold Spring Harbour and was published in the journal Genome Research last October. Dubbed ROMA (Representational Oligonucleotide Microarray Analysis), the procedure compares the copy number of small fragments of DNA. If the section of the genome is repeated, the copy number of the small fragments it contains will be greater.

Craig Venter, who led Celera Genomics' human genome research project, said, 'I think it's pretty important [research]. This helps us explain how, with very little sequence differences, we humans come up with such big differences among us'.