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Vol. LXIII, No. 17
August 19, 2011

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Researchers Develop Mouse with ‘Off Switch’ in Key Brain Cells

NIH-funded scientists have developed a strain of mice with a built-in off switch that can selectively shut down the animals’ serotonin-producing cells, which make up a brain network controlling breathing, temperature regulation and mood. The switch controls only the serotonin-producing cells and does not affect any other cells in the animals’ brains or bodies.

When the researchers powered down the animals’ serotonin cells, the animals failed to sufficiently step up their breathing to compensate for an increase of carbon dioxide in the air and their body temperatures dropped to match the surrounding temperature.

The finding has implications for understanding sudden infant death syndrome, or SIDS, which has been linked to low serotonin levels and is thought to involve breathing abnormalities and problems with temperature control. The study results appeared in the July 29 issue of Science.

In this British medical journal image, the head and shoulders of John Merrick, who became known as the Elephant Man, are illustrated.
In this British medical journal image, the head and shoulders of John Merrick, who became known as the Elephant Man, are illustrated.
Gene Variant ID’d in Proteus Syndrome

A team led by NHGRI researchers has identified the genetic mutation that causes Proteus syndrome, a rare disorder in which tissue and bone grow massively out of proportion. The discovery, which has implications for potential drug therapies and even cancer, appeared in the July 27 early online edition of the New England Journal of Medicine.

Proteus syndrome gained wide public attention in 1980, through the movie The Elephant Man, about a 19th century Londoner whom experts believe may have suffered from the disease.

Researchers found that a point mutation—a single- letter misspelling in the DNA of the genetic code—in the AKT1 gene activates the sporadic tissue growth characteristic of Proteus syndrome. Physicians named the condition for the Greek god who could transform his shape. There are fewer than 500 people with the disease in the developed world, where it can be tracked.

Unlike inherited disease-causing mutations, the gene variant that triggers Proteus occurs spontaneously in each affected individual during embryonic development. The severity of the disease depends on the timing during embryonic development that the genetic mistake occurs in a single cell and in which part of the developing organism.

NIH Researchers Trace Early Journey of Modulating Cells in Brain

Key cells in the brain region known as the hippocampus are formed in the base of the brain late in fetal life and undertake a long journey before reaching their final destination in the center of the brain shortly after birth, according to researchers at NIH.

The hippocampus is involved with attention, navigation and converting short-term memories to long-term memories. Interneurons, the brain cell population the researchers studied, regulate communication between networks of brain cells. Previous research suggests that brain cell networks in the hippocampus may be disrupted in developmental disorders, including autism, as well as in epilepsy, Alzheimer’s disease and schizophrenia.

“The hippocampus seems to be at the crossroads of many disorders affecting the brain,” said Dr. Chris McBain of NICHD. “With these findings, we can begin to understand how proper communication is established in the brain and to investigate why sometimes it breaks down in this critical area.”

The findings appeared in July in the Journal of Neuroscience.

New Method Proposed to Predict Fertility Rates

Researchers supported by NIH have developed a new statistical technique to forecast changes in fertility rates. The method mathematically compensates for uncertainty and is expected to allow governments to plan more reliably for the infrastructure and social services needed to accommodate large-scale population changes.

Conventional methods for predicting a country’s fertility rate are based on two considerations. The first is an average figure for the number of times a woman gives birth during a lifetime. The second is an estimation of how this number changes as a woman grows older. In addition, to account for the possibility of deviations, analysts have added and subtracted 0.5 children to the average rate predicted, creating a range of predictions. However, previous methods could not calculate how likely it was that such a variation would actually occur.

The new method is based on the idea that the transition from high to low fertility rates follows a similar pattern in all countries. The method uses a statistical formula to take into account historical fertility estimates and the likelihood of future trends. The findings appeared in July in the journal Demography.

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