Can you inherit a long life?

Parents may be passing more to their offspring than only DNA, study finds

Happy mother & son

Parents may be passing more to their offspring than their DNA. A new study shows some worms pass along non-genetic changes that extend the lives of their babies up to 30 percent.

Rather than changes to the actual genetic code, epigenetic changes are molecular markers that control how and when genes are expressed, or "turned on." These controls seem to be how the environment impacts a persons' genetic nature. For instance, a recent study on diet showed that what a mouse's parents ate affected the offspring's likelihood of getting cancer. Studies in humans have suggested that if your paternal grandfather went hungry, you are at a greater risk for heart disease and obesity.

The new study's results "could potentially suggest that whatever one does during their own life span in terms of environment could have an impact on the lives of their descendents," study researcher Anne Brunet, of Stanford University, told LiveScience. "This could impact how long the organism lives, even though it doesn't affect the genes themselves."

The study was conducted in the model organism C. elegans, a small, wormlike nematode often used in experiments as a stand-in for humans because of their genetic similarities. Even so, the researchers aren't sure how their results would apply to human life span. They are currently studying fish and mice to see if their findings hold true in different species.

Mutations that affect longevity in nematode parents
can impact the lifespan of descendants even if the initial mutation
is no longer present. This image represents a longevity
mark in the normal offspring of mutant nematodes.

Genes or epigenes?

Our DNA holds the code for life, but this code can be adapted based on how DNA is twisted together with proteins. Changes to these proteins are called "epigenetic," a word that literally means "on top of the genome." [ Epigenetics: A Revolutionary Look at How Humans Work ]

Modifications to proteins called histones that hold DNA together can turn genes off by adding a molecule called a methyl group (a carbon-hydrogen molecule), and can turn genes on by removing the methyl. These modifications can be caused by a variety of things in the environment, including diet or exposure to toxins.

The new study shows that, contrary to popular belief, some of these changes survive fertilization. Which ones survive, and how, are questions researchers are still trying to answer.

"What this finding suggests is that it's [the epigenome] not completely reset and there is epigenetic inheritance that isn't encoded by the genome that is sill transmissible between generations," Brunet said.

Inherited longevity 

The researchers found that when they mutated the protein complex that adds a methyl group to a specific histone protein, the nematodes lived up to 30 percent longer than the non-mutants. When the mutant nematodes reproduced with normal nematodes, their offspring (even those without the mutation) lived up to 30 percent longer. The methyl addition that caused the extended lifespan seemed to be passed down, even if the actual mutation wasn't.

For a nematode, which lives 15 to 20 days in the lab, an extra five or six days is a big boost. This would be like a human, instead of living to 80, living past 100.

The complex seems to turn off pro-aging genes, though what those genes are and how they work, the researchers aren't sure. "We really don't know yet what the mechanisms are, even in the parents, in which this complex manipulates life span," Brunet told LiveScience. "We do see genes that are involved in aging that are regulated by this complex."

Human implications 

While the researchers aren't sure about the protein's effect on human longevity yet, the finding is also important in studies of adult stem cells. Adult stem cells are normal cells that are 'reprogrammed' and supposedly wiped free of their epigenetic modifications. If this wiping process isn't thorough, leftover modifications could compromise therapies using these cells.

"The finding is fascinating," David Sweatt, a researcher at the University of Alabama at Birmingham, told LiveScience in an email. "The observations are also consistent with the emerging concept of 'soft inheritance,' whereby epigenetic mechanism may drive a molecular memory of ancestral experience over several generations."

Silvia Gravina, a researcher from the Albert Einstein College of Medicine in New York, suggested that epigenetic inheritance like that in the study could augment traditional "longevity" genes in human centenarians and their offspring.

"This finding supports the captivating and novel concept that health and general physiology can be affected not only by the interplay of our own genes and conditions of life, but also by the inherited effects of the interplay of our own genes and the environment of our ancestors," Gravina said, also by email.

Neither Sweatt nor Gravina was involved in the study, which was published Oct. 19 in the journal Nature.

Quoted from MSN

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Dark matter mystery deepens

Dark matter should be densely packed in the centers of galaxies. Instead, new measurements of two dwarf galaxies show that they contain a smooth distribution of dark matter.

Like all galaxies, our Milky Way is home to a strange substance called dark matter. Dark matter is invisible, betraying its presence only through its gravitational pull. Without dark matter holding them together, our galaxy’s speedy stars would fly off in all directions.

This artist's conception shows a dwarf galaxy
seen from the surface of a hypothetical exoplanet.
A new study finds that the dark matter in dwarf galaxies
 is distributed smoothly rather than being clumped
at their centers. This contradicts simulations
using the standard cosmological model known as lambda-CDM.
Credit: David A. Aguilar (CfA)

The nature of dark matter is a mystery — a mystery that a new study has only deepened.

“After completing this study, we know less about dark matter than we did before,” said Matt Walker from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

The standard cosmological model describes a universe dominated by dark energy and dark matter. Most astronomers assume that dark matter consists of “cold” (i.e. slow-moving) exotic particles that clump together gravitationally. Over time, these dark matter clumps grow and attract normal matter, forming the galaxies we see today.

Cosmologists use powerful computers to simulate this process. Their simulations show that dark matter should be densely packed in the centers of galaxies. Instead, new measurements of two dwarf galaxies show that they contain a smooth distribution of dark matter. This suggests that the standard cosmological model may be wrong.

“Our measurements contradict a basic prediction about the structure of cold dark matter in dwarf galaxies. Unless or until theorists can modify that prediction, cold dark matter is inconsistent with our observational data,” Walker said.

Dwarf galaxies are composed of up to 99 percent dark matter and only 1 percent normal matter like stars. This disparity makes dwarf galaxies ideal targets for astronomers seeking to understand dark matter.

Walker and Jorge Penarrubia from the University of Cambridge, United Kingdom, analyzed the dark matter distribution in two Milky Way neighbors — the Fornax and Sculptor dwarf galaxies. These galaxies hold one million to 10 million stars, compared to about 400 billion in our galaxy. The team measured the locations, speeds, and basic chemical compositions of 1,500 to 2,500 stars.

“Stars in a dwarf galaxy swarm like bees in a beehive instead of moving in nice, circular orbits like a spiral galaxy,” said Penarrubia. “That makes it much more challenging to determine the distribution of dark matter.”

Their data showed that in both cases, the dark matter is distributed uniformly over a relatively large region, several hundred light-years across. This contradicts the prediction that the density of dark matter should increase sharply toward the centers of these galaxies.

“If a dwarf galaxy were a peach, the standard cosmological model says we should find a dark matter “pit” at the center. Instead, the first two dwarf galaxies we studied are like pitless peaches,” said Penarrubia.

Some have suggested that interactions between normal and dark matter could spread out the dark matter, but current simulations don’t indicate that this happens in dwarf galaxies. The new measurements imply that either normal matter affects dark matter more than expected, or dark matter isn’t “cold.” The team hopes to determine which is true by studying more dwarf galaxies, particularly galaxies with an even higher percentage of dark matter.

Quoted from Astronomy Magazine

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VISTA finds new globular star clusters and sees right through the heart of the Milky Way

This survey has also turned up the first star cluster that is far beyond the center of the Milky Way on the other side of our galaxy.

This image from VISTA is a tiny part of the VISTA Variables
in the Via Lactea (VVV) survey that is systematically studying
the central parts of the Milky Way in infrared light.
On the right lies the globular star cluster UKS 1
and on the left lies a much less conspicuous new discovery,
VVV CL001 — a previously unknown globular.
The new globular appears as a faint grouping of
stars about 25% of the width of the image from the left edge,
and about 60% of the way from bottom to top.
Credit: ESO/D. Minniti/VVV Team

Two newly discovered globular clusters have been added to the total of just 158 known globular clusters in our Milky Way. They were found in new images from the European Southern Observatory’s (ESO) VISTA survey telescope as part of the variables in the Via Lactea (VVV) survey. This survey has also turned up the first star cluster that is far beyond the center of the Milky Way and whose light has had to travel right through the dust and gas in the heart of our galaxy to get to us.

The dazzling globular cluster called UKS 1 dominates the right-hand side of the image from ESO’s VISTA survey telescope at the Paranal Observatory in Chile. But if you can drag your gaze away, there is a surprise lurking in this rich star field — a fainter globular cluster that was discovered in the data from one of VISTA’s surveys. You will have to look closely to see the other star cluster, which is called VVV CL001 — it is a small collection of stars in the left half of the image.

But VVV CL001 is just the first of VISTA’s globular discoveries. The same team has found a second object, dubbed VVV CL002. This small and faint grouping may also be the globular cluster that is the closest known to the center of the Milky Way. The discovery of a new globular cluster in our Milky Way is rare. The last one was discovered in 2010, and only 158 globular clusters were known in our galaxy before the new discoveries.

These new clusters are early discoveries from the VVV survey that is systematically studying the central parts of the Milky Way in infrared light. Dante Minniti leads the VVV team from the Pontifica University of Chile and Philip Lucas from the University of Hertfordshire, United Kingdom.

As well as globular clusters, VISTA is finding many open, or galactic, clusters, which generally contain fewer, younger stars than globular clusters and are far more common. Another newly announced cluster, VVV CL003, seems to be an open cluster that lies in the direction of the heart of the Milky Way, but much further away, about 15,000 light-years beyond the center. This is the first such cluster to be discovered on the far side of the Milky Way.

Given the faintness of the newly found clusters, it is no wonder that they have remained hidden for so long; up until a few years ago, UKS 1, which easily outshines the newcomers, was actually the dimmest known globular cluster in the Milky Way. Because of the absorption and reddening of starlight by interstellar dust, these objects can only be seen in infrared light and VISTA, the world’s largest survey telescope that is ideally suited to searching for new clusters hidden behind dust in the central parts of the Milky Way.

One intriguing possibility is that VVV CL001 is gravitationally bound to UKS 1, making these two stellar groups the Milky Way’s first binary globular cluster pair. But this could just be a line-of-sight effect with the clusters actually separated by a vast distance.

Quoted from Astronomy Magazine

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Blue stragglers: Astronomers discover how mysterious stars stay so young

Scientists report that a mechanism known as mass transfer explains the origins of these old stars that still burn hot and blue.

Mysterious “blue stragglers” are old stars that appear younger than they should — they burn hot and blue. Several theories have attempted to explain why they don’t show their age, but, until now, scientists have lacked the crucial observations with which to test each hypothesis.

An artist's conception showing a blue straggler
 being created by mass transfer in a binary star system.
The giant star, seen in the upper left of the illustration,
 has lost hold of its outer envelope.
This material is pulled towards its partner,
forming an accretion disk, and is eventually
consumed by the "proto-blue straggler."
Soon the giant star will donate the remainder of
its envelope, leaving only the half-solar-mass
 white dwarf core
(shown peaking through the giant's tenuous envelope)
as the companion to the blue straggler.
Credit: Aaron M. Geller

Armed with such observational data, Aaron M. Geller from Northwestern University in Chicago, Illinois, and Robert Mathieu from the University of Wisconsin-Madison report that a mechanism known as mass transfer explains the origins of the blue stragglers. Essentially, a blue straggler eats up the mass, or outer envelope, of its giant-star companion. This extra fuel allows the straggler to continue to burn and live longer while the companion star is stripped bare, leaving only its white dwarf core.

The majority of blue stragglers in their study are in binaries — they have a companion star. “It’s really the companion star that helped us determine where the blue straggler comes from,” said Geller. “The companion stars orbit at periods of about 1,000 days, and we have evidence that the companions are white dwarfs. Both point directly to an origin from mass transfer.”

The astronomers studied the NGC 188 open cluster, which is in the constellation Cepheus, situated in the sky near Polaris, the North Star. This cluster is one of the most ancient open star clusters, but it features these mysterious, young-looking blue stragglers.

The cluster has around 3,000 stars, all about the same age, and has 21 blue stragglers. Geller and Mathieu are the first to use detailed observational data from the WIYN Observatory in Tucson, Arizona, of the blue stragglers in NGC 188.

They used the information to analyze and compare the three main theories of blue straggler formation: collisions between stars, mergers of stars, and mass transfer from one star to another. The only one left standing was the theory of mass transfer.

The light from the blue stragglers’ companion stars is not actually visible in Geller and Mathieu’s observations. While the companions haven’t been seen directly, their effect on the blue stragglers is evident: Each companion pulls gravitationally on its blue straggler and creates a “wobble” as it orbits, and this allows astronomers to measure the mass of the companion stars. The WIYN data show that each companion star is about half the mass of the Sun, which is consistent with a white dwarf.

The other two origin theories — collisions and mergers — require the companion stars to be more massive than what is observed. In fact, in both scenarios, some of the companion stars could be bright enough to be visible in the WIYN data, which is not the case.

“We think we have a good understanding of stellar evolution, but it doesn’t predict blue stragglers,” Geller said. “People have been trying to explain the origin of blue stragglers since their discovery in 1953, and now we have the detailed observations needed to identify how they were created. I’ve always enjoyed trying to get to the bottom of a mystery.”

“As so often happens in astronomy, it is the objects that you don’t see that provide the critical clues,” said Mathieu. “Now we will use the Hubble Space Telescope to search for the ultraviolet light in which white dwarf secondary stars shine.”

Geller, Mathieu, and their colleagues will have, in about a year’s time, observations from Hubble that will tell them if the blue stragglers’ companions are, indeed, white dwarfs.

Quoted from Astronomy Magazine

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