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Vol. LIX, No. 11
June 1, 2007

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  The genome of a South American species of opossum is proving useful in comparative studies with the human genome.  
  The genome of a South American species of opossum is proving useful in comparative studies with the human genome.  
The Power of ‘Junk’

Thanks to new genetic findings in marsupials, researchers have learned that most innovations leading to the human genome sequence lie in areas that until recently were labeled “junk” DNA. An international team supported by NHGRI announced in the May 10 issue of Nature the publication of the first genome sequence of a marsupial—specifically, one belonging to a South American species of opossum. By comparing the marsupial genome to genomes of non-marsupials, like humans, researchers are able to understand better the way mammalian genomes have evolved over millions of years. The key finding from the comparison: the vast majority of recent genetic innovation in our genome lies not in protein-coding genes, but in regions that don’t contain genes at all, leading to their “junk” moniker. Marsupials are the closest living relatives of placental mammals, offering a unique view of our own genome’s evolution.

More Testing Needed

Two recent findings from NIH researchers point to worrisome rates in necessary testing and treatment. In an online report in the journal Cancer, researchers, led by NCI’s Dr. Nancy Breen, showed that after rapid increases in reported use of mammography by women in the U.S. since 1987, the percentage of women 40 and older who reported having a mammogram within the last 2 years slipped from 70 percent in 2000, to 66 percent in 2005. Though this is a relatively small decline, researchers said the drop is still cause for concern because it signals a change in direction. The findings were based on a survey of about 10,000 U.S. women over age 40 conducted by the CDC.

And Treatment, Too

Meanwhile, a recent survey conducted by NIDA and NIAAA showed that only 8 percent of people identified as drug abusers and fewer than 40 percent of those diagnosed with drug dependence have ever had any kind of intervention or treatment. These survey results, published in the May issue of the Archives of General Psychiatry, also show that rates of drug abuse and dependence are generally higher among certain populations, including men, respondents ages 18 to 44 years and people who have never married. Researchers said these findings suggest certain groups are more vulnerable and should therefore be targeted for early intervention efforts.

Defining Bipolar Disorder

In the same issue of the Archives of General Psychiatry, an NIMH-funded study reported that bipolar disorder may be both inaccurately characterized and improperly treated. Using data from a nationwide survey of mental disorders among 9,282 Americans ages 18 and older, researchers determined that the illness may be more accurately characterized as a “spectrum” disorder because it manifests itself in multiple ways. And while the study showed most respondents with the illness reported receiving treatment of some kind, not everyone received treatment considered optimal for bipolar disorder. Up to 97 percent of those who had some type of bipolar illness said they had coexisting psychiatric conditions— like anxiety, depression or substance abuse disorders—and many received treatment for these conditions instead of for bipolar disorder. The study points to the need for better screening tools and procedures for identifying the disorder, researchers said.

However, this month NIMH also reported more positive news for bipolar disorder. Research published online in Molecular Psychiatry revealed results from the first genome-wide study of the illness. It showed that the likelihood of developing the disorder depends in part on combined, small effects of variations in many different genes in the brain, none of which is powerful enough to cause the disease by itself. Targeting the enzyme produced by one of these genes, called DGKH, could lead to the development of new, more effective medicines.

Visualizing the ‘Claw’

Finally, electron tomography, an advanced imaging technique, has allowed NCI researchers to visualize an “entry claw,” a structure formed between the human immunodeficiency virus and the cell that it infects. This ability to see virus-host interaction at the molecular level not only gives researchers insight into how HIV and related viruses interact with proteins on the surface of cells and enter the host cells to integrate their DNA, but also gives clues as to how to improve the design of anti-HIV therapy. Further, it demonstrates that tools like electron tomography have the potential to help scientists see the subcellular effects of many different diseases, including cancer. The findings were published in the May 4 issue of PLoS Pathogens. —

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