This week’s papers from Boston labs

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T. rex fossil yields 68-million-year-old protein

Scientists have long thought that no organic material could survive for more than a million years, but protein fragments isolated from a 68-million-year-old Tyrannosaurus rex bone have proven them wrong.

Researchers from Harvard Medical School and Beth Israel Deaconess Medical Center collaborated with paleontologist Mary Schweitzer from North Carolina State University to isolate and analyze tiny amounts of collagen, protein found in connective tissue, from a fossilized femur excavated in Montana in 2003.

This 68-million-year-old fossilized femur from a Tyrannosaurus rex still had intact protein for analysis. (Credit: Science)

The team used mass spectrometry to look at the protein’s chemical composition and found that its amino acid sequence most closely matched that of bird collagen, giving researchers more support for the contention that modern birds are the living descendants of dinosaurs.

The protein apparently survived all this time because of collagen’s inherent chemical stability and the favorable fossilization conditions of the sample. The researchers also reported the amino acid sequence of collagen from a half-million-year-old mastodon fossil.

These results show how the analysis of organic molecules from long-dead species could lead to further insights into evolution. Paleontologists should rethink how they handle and store fossils, the authors write, if they want to preserve and discover new clues in old bones. While the collagen from their T. rex bones persisted for millions of years in the undisturbed fossil, it took only a few years to degrade once the bones were dug up.

The research appears in two articles in today’s Science. Pat McCaffrey

Fruit flies adjust their clocks with changing seasons

As the days lengthen and shorten with the changing seasons, your body clock adjusts so that you feel awake and active during the day and wind down at night. New research from Brandeis University on fruit flies reveals how the brain responds to changes in light and season to coordinate shifts in behavior.

All animals have circadian clocks, groups of neurons in the brain that drive daily oscillations in body temperature and metabolic activity, as well as waking and sleeping cycles. Michael Rosbash and colleagues had previously shown that fruit flies possess two such sets of cells. One set regulates the flies’ characteristic morning activity, while the other controls their evening movements.

The latest work from Rosbash and collaborators shows that these two groups of brain cells alternate in controlling the internal rhythms depending on the presence or absence of light. The cells in charge of morning activity take over during periods of darkness and sense the onset of light. The other group of cells dominates when light is present and responds when darkness falls. Together, the two groups of cells form a neural network that enables these creatures to flexibly respond to changing day length. A similar neural network in other animals could regulate seasonal behaviors including mating, migrating, or hibernating.

The researchers altered the activity of a regulatory gene in one set of cells at a time and looked for changes in the patterns of fly activity in response to varying levels of light that mimicked seasonal changes. They found that, depending on the relative amounts of light and darkness, one set of neurons or the other became the master regulator, telling the flies when to venture out and when to rest.

These results may help explain the complex interaction between seasons, daylight, and mood in humans. The fruit fly gene targeted by the researchers has an equivalent in humans that is involved in seasonal affective disorder, a form of depression that usually occurs in winter. A mood-stabilizing drug used to treat this disorder, lithium, inhibits the activity of this gene.

The research is reported in this week’s Cell. Pat McCaffrey

Astrophysicists spot earliest signs of dark energy

Using the Hubble Space Telescope, a team of researchers, including two from the Harvard-Smithsonian Center for Astrophysics, has discovered 21 supernovas, distant exploding stars, most of which are at least half as old as the universe. This quadruples the number of known supernovas that are more than seven billion years old, and opens up a unique view on what was happening in the early universe.

This discovery reveals that dark energy—thought to be driving our universe to expand at a faster rate—has been at work during most of the universe’s 14-billion-year history. Scientists were astounded in 1998 when they found that the universe was expanding at an accelerated rate and not at a slower rate, as they had expected. This latest study is the earliest evidence of this accelerating expansion.

Researchers have given the name “dark energy” to the force behind this cosmic acceleration, but no one is sure what it really is, except that it doesn’t fit with existing cosmological theories. For now, physicists are trying to get a handle on dark energy’s effects, such as the accelerating expansion of the universe.

By looking at the brightness and color of supernovas, the researchers could tell how far away they were and how quickly they were moving away from us. By looking at these very old supernovas, the researchers were able to gauge the universe’s rate of expansion as far back as 9 or 10 billion years ago.

The results also add confidence to earlier measures of cosmic acceleration, showing that dark energy’s effect has been fairly constant over most of the universe’s history. The research was published this week in the Astrophysical Journal. Mason Inman