DNA structure (Image: Michael Ströck via Wikimedia Commons)

Prevailing wisdom holds that every cell in the body contains identical DNA.

But Yale researchers say they examined skin stem cells and found a number of genetic variations in a variety of skin tissue.

The study, published in Nature, could have profound implications for genetic screening.

“We found that humans are made up of a mosaic of cells with different genomes,” said lead author Flora Vaccarino, M.D., from the Yale Child Study Center. “We saw that 30 percent of skin cells harbor copy number variations (CNV), which are segments of DNA that are deleted or duplicated. Previously it was assumed that these variations only occurred in cases of disease, such as cancer. The mosaic that we’ve seen in the skin could also be found in the blood, in the brain, and in other parts of the human body.”

It’s been long believed that all of our cells have the very same DNA sequence.

Other scientists conducting similar genetic research have theorized the DNA sequence of a cell could be modified during the cell’s development – when DNA is copied from a mother cell to a daughter cell.  These many changes to a cell’s original DNA, they say, could affect an entire group of genes.

While it’s difficult for scientists to actually test these theories, the Yale researchers say they have been able to do so for their new study.

To reach their findings, the research team used whole genome sequencing – a genome is a complete set of hereditary information – to study induced pluripotent stem cells (iPS), which are genetically engineered stem cells developed from a mature-differentiated cell.

The team grew cells taken from the inner upper arms of people from two families. For two years, the researchers examined their genetically engineered iPS cell lines, compared them to the original skin cells, and noted any differences between each cell’s DNA.

The team also conducted further experiments to see what might have caused the differences to occur.

While the research in the project outlined in this recent study was limited to finding variations in DNA sequencing within skin cells, the Yale team is continuing its studies to see if these same DNA variations can be found in developing brain cells of animals as well as humans.

A western honeybee (Photo: Wolfgang Hägele via Wikimedia Commons)

A new study finds prolonged antibiotic use by beekeepers might play a role in the mysterious drop in honey bee populations in the United States.

Yale researchers found genetic evidence that helpful bacteria, which normally live the bellies of honeybees, have become highly resistant to the antibiotic tetracycline, possibly weakening the bees’ ability to fight disease.

Researchers say decades of use may have unknowingly encouraged antibiotic resistance by genetically altering the beneficial bacteria.

Past studies show helpful bacterial play an important role in protecting the honeybee by neutralizing toxins found in their diets while also helping fight off various pathogens.

The  researchers have identified eight different tetracycline resistance genes among U.S. honeybees that were exposed to antibiotics.  Those same resistance genes were missing in bees from countries where antibiotic use is banned.

“It seems to be everywhere in the U.S.,” says Nancy Moran of Yale University, a senior author on the study. “There’s a pattern here, where the U.S. has these genes and the others don’t.”

In the 1950s, beekeepers started using the antibiotic oxytetracycline, a compound similar to tetracycline, which is commonly used in humans. They were trying to fight a devastating bacterial disease called foulbrood, which can wipe out a hive more quickly than beekeepers can react to the infection.

But after years of use  the microorganisms eventually acquired a resistance to tetracycline, possibly weakening the honeybee’s resistance to other diseases.

“It seems likely this reflects a history of using oxytetracycline since the 1950s,” says Moran. “It’s not terribly surprising. It parallels findings in other domestic animals, like chickens and pigs.”

A beekeeper tends to a beehive. (Photo: Emma Jane Hogbin via Creative Commons at Flickr)

The researchers took bee samples from the Czech Republic, New Zealand and Switzerland, which do not allow their beekeepers to use the antibiotics.

Researchers found  those bees had only two or three different resistance genes and even then only in very low numbers, suggesting that prolonged antibiotic use in the US bees may have played a role in developing the resistance genes.

Moran  points out that the antibiotic-resistant genes researchers found in the bellies of the honeybee do not pose a direct risk to humans.

Those microorganisms, according to Moran, “don’t actually live in the honey, they live in the bee. We’ve never actually detected them in the honey. When people are eating honey, they’re not eating these bacteria.”

Nancy Moran joins us this weekend on the radio edition of Science World.  She tells us more about how treatment meant to strengthen honeybee hives in the U.S. may have actually weakened them instead. Tune in (see right column for scheduled times) or check out the interview below.

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The newly discovered planet PH1 is depicted in this artist’s rendition transiting the larger of the its two host stars. Left of the planet, off in the distance, is a second pair of stars that orbit PH1. (Image: Haven Giguere/Yale)

The recent discovery of a four-star planet highlights the growing value of citizen scientists, non-professional enthusiasts – including  hobbyists, educators and amateur scientists – who participate in scientific endeavors.

The discovery of the extrasolar planet dubbed PH1, which orbits twin suns and is itself orbited by a second distant pair of stars, was made through the combined efforts of volunteer citizen scientists and  professional astronomers.

The amateur scientists behind the sighting of the phenomenon, called a “circumbinary planet in a four-star system,” were able to get involved with astronomical research through the website Planethunters.org, a collaboration between Yale University and the online citizen science project Zooniverse.

“Planet Hunters is a symbiotic project, pairing the discovery power of the people with follow-up by a team of astronomers,” says Debra Fischer, a planet expert and professor of astronomy at Yale, who helped launch the website in 2010. “This unique system might have been entirely missed if not for the sharp eyes of the public.”

Through Planethunters.org, volunteers help professional astronomers sift through mountains of data  gathered by NASA’s Kepler space mission.

That assistance includes brightness measurements, or “light curves,” for more than 150,000 stars, taken by instruments aboard Kepler  every 30 minutes.

Artist’s rendition of the newly discovered circumbinary planet PH1 that orbits two suns (upper left) and is 5,000 light years from Earth. (Image: Haven Giguere/Yale)

The Planet Hunters pour through the data looking for possible transit events, a brief dip in brightness that occurs when a planet or other celestial body passes in front of the star.

“The thousands of people who are involved with Planet Hunters are performing a valuable service,” says Jerome Orosz, associate professor of astronomy at San Diego State University and co-author of the paper outlining PH1’s discovery. “Many of the automated techniques used to find interesting features in the Kepler data don’t always work as efficiently as we would like. The hard work of the Planet Hunters helps ensure that important discoveries are not falling through the cracks.”

PH1, some 5000 light years from Earth, has been described by astronomers as a gas giant planet slightly bigger than Neptune.  It takes the extrasolar planet 138 days to complete an orbit around its two host stars, which have masses about 1.5 and 0.41 times that of the sun and also circle each other once every 20 days.  The two distant stars that orbit the new-found planet are about 144,840,960,000 km away, roughly 1000 times the distance between the Earth and the Sun.

Yale’s Meg Schwamb of Yale, the lead author of the paper said that the circumbinary planets that are being discovered are the extremes of planet formation.

“The discovery of these systems is forcing us to go back to the drawing board to understand how such planets can assemble and evolve in these dynamically challenging environments.”