Japan Team Touts Benefits of Artificial Chromosome

Japanese scientists said Friday they had built an artificial chromosome, which might aid efforts to use gene therapy to treat diseases such as muscular dystrophy and cystic fibrosis.

Hiroshi Masumoto of Nagoya University in Japan and colleagues said they hope their chromosome might be used to deliver some form of gene therapy.

Every human cell contains 46 chromosomes. These, in turn, carry the genes. Everyone has some “defective” genes, but some defects have more serious effects than others.

One inherited defect causes cystic fibrosis, for example, a disease that causes the overproduction of mucus, leading to breathing and digestive problems and eventual death.

Sometimes replacing just a single gene would cure a disease, but getting the gene to “take” permanently has been impossible so far. Some scientists think that an extra miniature chromosome, carrying the therapeutic gene or genes, could do the trick.

Writing in the journal Nature Biotechnology, Masumoto’s team said they had engineered a miniature chromosome and said it was stable in human cells.

Also, it did not take on DNA from other chromosomes.

For a chromosome to work, it must have the end part, known as a telomere, and a middle part, known as a centromere.

In previous experiments, scientists have been able to throw the centromeres and telomeres into a cell and let it rearrange them into chromosomes.

But in the past, the cell always threw in random bits of DNA, making it impossible to predict what the resulting chromosome would look like.

Masumoto said his chromosomes do not have this problem.

The next step would be to try to add a therapeutic gene and see if it works.