Transplanting a Genome
Scientists successfully transform one bacterial species into another

SOURCE: “Genome Transplantation in Bacteria: Changing One Species to Another”
John I. Glass et al.
Science online, June 28, 2007

RESULTS: Scientists at the J. Craig ­Venter Institute in Rockville, MD, have transferred the entire genome of one bacterium into another bacterium. The host bacterium took on characteristics of the donor–for example, producing proteins specific to that species.

WHY IT MATTERS: Venter and his colleagues aim to build genomes from scratch and transplant them into bacterial cells in order to create custom­-made microörganisms, including ones that produce fuel. Successful genome transplant techniques will be necessary to complete this process.

METHODS: The scientists isolated the DNA of one species of mycoplasma, a type of bacterium with a very small genome, and gave it an additional gene to make it resistant to an antibiotic. The DNA was then transplanted into a related mycoplasma ­species. As the host bacteria grew and divided in the presence of the antibiotic, cells carrying only the species’ original chromosomes died, leaving just the cells with the transplanted chromosome.

NEXT STEPS: Venter Institute researchers will next try to determine whether or not genome transplantation is possible in other species of bacteria. They are also developing a synthetic version of the genome of a different species of mycoplasma, which they will attempt to transplant as well.

Genes for Several Common Diseases
A study of seven illnesses, including diabetes and cardiovascular disease, identifies possible culprits

SOURCE: “Genome-Wide Association Study of 14,000 Cases of Seven Common Diseases and 3,000 Shared Controls”
The Wellcome Trust Case Control Consortium
Nature 447: 661-678

RESULTS: A massive genetic study carried out in the United Kingdom pinpointed 24 genetic markers that increase risk for seven common illnesses. The study found one marker for bipolar disorder, one for coronary-artery disease, nine for Crohn’s disease, three for rheumatoid arthritis, seven for type 1 diabetes, and three for type 2 diabetes.

WHY IT MATTERS: Unlike rare diseases such as Huntington’s, where a single genetic variation guarantees that a carrier will be afflicted, common diseases are triggered by a complex array of factors, including multiple genes each exerting a modest effect. The new study illustrates the success of a new approach to gene hunting known as genome-wide association, in which scientists scour the entire genome for ­disease-­specific variations. The vast scope of such studies–in this case, almost 10 billion pieces of DNA–provides enough statistical power for researchers to find genetic variations that raise the risk of disease by a modest amount.

METHODS: The scientists used gene chips to analyze 500,000 genetic markers in each of 17,000 people. To identify genetic variations linked to specific diseases, they compared the DNA of 2,000 patients who had one of the diseases with that of 3,000 healthy controls.

NEXT STEPS: The researchers will try to confirm additional genetic variations hinted at in the current study by analyzing genomic information from larger numbers of people.