This week’s papers from Boston labs

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MicroRNA reins in cancer gene

An exciting area of research in RNA biology is focused on figuring out the role of a recently discovered large class of small RNA molecules, called microRNA. The molecules have emerged in our understanding as a major gene regulator, controlling about one third of the genome.

Researchers have known that microRNA levels are out of whack in cancer cells, but because one microRNA can control hundreds of genes, they couldn’t tell exactly what role the microRNAs played in cancer.

Now, a group from MIT and the Whitehead Institute has found that one microRNA stops tumor growth by restraining the activity of a cancer-causing gene, marking the first time that microRNA has been implicated in bringing about cancer. The work also reveals how some genetic mutations that were previously unrecognized can be important in cancer.

The investigators homed in on one potential target gene, HMGa2, which is shortened in many tumors, losing part of its protein-coding sequence. Previous work pointed to the truncated protein product as the cancer-causing culprit.

But the researchers realized that besides the coding regions, the missing bits also contain several docking sites for a microRNA. With those sites gone, they showed, the HMGa2 gene could produce more protein. They found that it was the increased level of protein, not the size of the protein, that drove cells to form tumors. The loss of microRNA regulation is enough to transform normal cells into cancerous cells.

The results should spur a hunt for similar mutations in other cancer-causing genes.

The report, from Christine Mayr, Michael Hemann, and David Bartel, appeared online this week in Science. Pat McCaffrey

Medieval Islamic artists beat Western scientists by 500 years in discovery

The intricate patterns of tiles on the walls of ancient mosques and shrines reveal that Islamic artists of the Middle Ages created a complex class of structures called quasicrystals, which Western physicists discovered some 500 years later, according to a paper in this week’s Science.

Darb-i Imam shrine in Isfahan, Iran (Image courtesy of K. Dudley and M. Elliff)

In regular crystals like diamonds, all the atoms fit together in a regular, repeating pattern. But in quasicrystals, the pattern never repeats itself exactly. Before physicists discovered quasicrystals, famed U.K. mathematician Roger Penrose proved their existence mathematically in the 1970s, using sets of tiles covering a surface.

Now two physicists say that Islamic artists working with tiles may have discovered quasicrystal structures in the Middle Ages. Peter Lu at Harvard University became intrigued by the patterns of tiling, called girih, on a mosque while visiting Uzbekistan. By analyzing a few thousand photographs of tiling on various buildings from Turkey to Afghanistan, Lu and Peter Steinhardt of Princeton University found that the patterns of tiles displayed telltale signs of quasicrystals, such as pentagons and 10-pointed stars. They also found that one shrine in Iran had a true quasicrystal pattern on it.

The physicists examined scrolls on which medieval Islamic artists sketched their designs and found that they were using a tiling pattern similar to Penrose’s to create the complex patterns. Still, they say it’s not clear how well the artists understood the underlying structures. Mason Inman

No sign of water on faraway planets

Astrophysicists have gotten the first direct glimpse of the atmospheres of planets outside our solar system, and their results are surprising. Based on accepted models of planet formation, they expected to see signs of water vapor but didn’t find any.

In two new studies, Boston researchers, using the Spitzer Space Telescope, measured a broad swath of wavelengths of infrared light emitted by two extrasolar planets. They were searching for the wavelengths of light absorbed by specific atmospheric components, such as water vapor. These studies are the first to directly analyze the light emitted by planets outside our solar system.

A team co-led by David Charbonneau of the Harvard-Smithsonian Center for Astrophysics looked at one of these planets, HD 189733b, in a paper

accepted by the Astrophysical Journal Letters_. Another team, which includes Sara Seager of MIT, describes similar findings with the planet, HD 209458b, orbiting a different star, in this week’s "_Nature":https://www.nature.com/doifinder/10.1038/nature05636.

The Nature paper provides a possible explanation for the unexpected results. The researchers saw signs of high levels of silicates, molecules containing silicon and oxygen, in the atmosphere. Their best guess is that these planets are shrouded in clouds of silicate—basically, rock dust—making them black all over and shrouding the signatures of other molecules in the atmosphere. Mason Inman