Amid all the As, Ts, Cs, and Gs of the genetic code, HHMI researchers were startled to find something new. Scientists have long known that modification of these four standard nucleotides—the building blocks of DNA—can determine when genes are turned on or off inside cells. The best-recognized modification is the addition of a small cluster of atoms known as a methyl group to the nucleotide cytosine (C), converting it to methylcytosine. The discovery of a previously unknown nucleotide, called hydroxymethylcytosine, inside animal cells suggests a new mechanism for regulating gene expression.
New Nucleotide Discovered
Scientists Probe Insect Olfaction
Blocking an insect’s sense of smell could prevent it from spreading disease or ravaging crops by interfering with its means of navigation—that’s one reason scientists seek to understand how insects detect odors. In the fruit fly, the best-studied odor detectors, odorant receptors, are found on only about 70 percent of olfactory neurons. Until recently, the remaining 30 percent remained a mystery. That knowledge gap was filled when researchers revealed that molecules called ionotropic receptors, whose structure is very different from that of an odorant receptor, allow these “mystery neurons” to respond to specific smelly cues.
Toward a Safer Prenatal Test for Down Syndrome
A prenatal blood test that scans the small amount of fetal DNA in the mother’s blood to determine whether the fetus’s cells contain extra chromosomes could offer a safer and faster alternative to invasive tests such as amniocentesis. The new test, which uses high-throughput gene sequencing technology to measure the amount of DNA from each chromosome present in the blood, accurately detected Down syndrome and two other serious chromosomal defects in a small study of pregnant women.
Genetic Risk Factors for Brain Aneurysm ID’d
Yale University School of Medicine
The first genome-wide search for genetic variations associated with brain aneurysm—a potentially fatal bulge in a blood vessel—could help doctors identify people at the greatest risk of experiencing one. A study of more than 10,000 people revealed three genetic factors that together can increase an individual’s likelihood of developing a brain aneurysm up to threefold. Knowing which patients should be screened could help clinicians find aneurysms while they can still be surgically removed.
Genetic Switch Could Treat Sickle Cell Disease
Children’s Hospital Boston
In a discovery that could improve treatments for certain life-threatening forms of anemia, HHMI researchers identified a genetic switch that can restore production of a form of hemoglobin that usually is made only by fetal cells. Shortly after birth, most infants stop producing the fetal form of hemoglobin, the blood protein responsible for transporting oxygen, and begin manufacturing the slightly different “adult” version. In rare instances, however, an individual can produce fetal hemoglobin through adulthood. In patients with sickle cell disease and beta-thalassemia, the presence of fetal hemoglobin is associated with milder disease. Researchers found that silencing BCL11A, the first known genetic regulator of the human hemoglobin switch to be discovered, increased fetal hemoglobin up to 40 percent.