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Gene Mutations Can Mean Longer Life March 4, 2008

Posted by Mrs Weird Scientist in Genetics, Human Body, Tough Stuff.
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While they won’t make someone live forever, researchers recently identified some variations in genes that can allow people to live longer. Your genes are your special and unique instructions that determine things like your hair and eye color.

Say Hello To Centenarians

Elderly Nir Barzilai and his team are from the Albert Einstein College of Medicine, which is part of Yeshiva University in New York. Their work involved research subjects of Ashkenazi Jewish descent who were all 100 years of age or older. The fancy term we like to use for people in this age bracket is centenarian. Barzilai and his colleagues identified two gene mutations in the centenarians. If you’re a keen bean, you can read the full, more technical version in the Proceedings of the National Academy of Sciences.

Mutations Can Be Good

You might be wondering to yourself that it seems odd for a mutation to result in greater longevity – something we consider beneficial! The word mutation can leave us thinking of disease, death and just generally bad stuff. While this is often the case, genetic mutations can also lead to positive changes. It’s thought that these changes occur to help humans or other organisms evolve and better adapt to their environment.

Looking Inside The Body

DNA In this study, researchers found that the two mutations affect a receptor for insulin-like growth factor 1 (IGF-1). What does IGF-1 do? If you’re thinking it might influence growth, you’re definitely on the right track. IGF-1 is a guiding force in your body’s growth and maturity. It’s especially dominant during puberty and directs the intense growth and development that occurs during the adolescent years. So, what if the receptor stops working properly, as in the case of the centenarians? If the receptor is just a wee bit faulty, the result is that IGF-1 doesn’t effectively bind to the receptor. Low and behold, the pathway to aging and maturation doesn’t proceed at the same pace and ultimately, it is slowed.

For my male readers, don’t get too hopeful you’ve got the gene mutations. Thus far, the carriers identified are all women. Even more interesting is that the centenarians were shorter than an average woman. These women were approximately 2.5 centimeters shorter than the rest of the population. It makes sense, however, given the role of IGF-1 during the huge pubertal growth spurt.

Our Obsession

Injection In westernized societies, we’re absolutely obsessed with anti-aging and finding the next product to decrease aging – whether it’s the visible, aesthetic signs of aging or the internal, physiological ones. Ironically, people have been getting injections of growth hormone for many years now, with the belief that it slows down the aging process. Given that Barzilai’s study showed it was the people with lower levels of growth hormone who are living longer, these injections could potentially be quite dangerous.

We’re Not Alone

Another thing to keep in mind is that humans are not the only ones with these types of mutations. Worms, flies and mice have similar faulty genes that increase longevity. In the coming years, researchers will probably be in a mad flurry to investigate the genes in other centenarian populations around the world. One of the hopes is to discover strategies to reduce aging in the general population. I guess for now though, I’ll just have to fake it by sticking with my anti-aging face cream!

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What A Lovely Forehead You Have August 4, 2007

Posted by Mrs Weird Scientist in Evolution, Genetics, Human Body, Think About It.
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We can give thanks to chance that we don’t have the heavily browed foreheads of our Neanderthal relatives. Any guesses why that is? Read on to find out!

A Quick Background

Neanderthal Skull Since modern humans and Neanderthals became isolated from one another – approximately half a million years ago – lots of changes have occurred and the two have mostly gone their separate ways, genetically speaking. Given that scientists are such curious and meddling creatures, they are constantly investigating how these changes happen and they continue to search (and argue!) for the reasoning behind it all. A new study published in the Journal of Human Evolution has shed some light on the skull differences between modern humans and Neanderthals. The conclusion? Good, old chance. Pun fully intended.

Lets Check Out Some Skulls

Timothy Weaver of the University of California, Davis, and his research team analyzed a lot of skulls! They compared 37 measurements of modern human skulls with Neanderthal skulls and calculated the mean divergence, which is just the average difference between the measurements. Next, they took a separate sample of modern human skulls, compared those 37 measurements within the sample, and calculated the mean divergence. Finally, they contrasted their two calculations to figure it all out. The researchers’ conclusion? Genetic drift is responsible for the skull differences, not positive natural selection. With positive natural selection, certain traits get carried on from one generation to the next as a response to changes in the environment. Genetic drift is different though. With genetic drift, physical features just randomly change. There’s no environmental driving force like you would see with positive natural selection.

Neanderthal and Human Skulls

Credit: All images by Encyclopaedia Britannica. The picture at the very top shows a Neanderthal skull. The one directly above depicts the same, but also shows the skeleton of a modern human leering in the background!

Old Research Versus New

In the past, researchers had thought that these particular cranial differences were due to natural selection that occurred for other reasons, such as Neanderthals’ use of teeth as tools! Also, anthropologists had considered that modern human speech drove the changes. According to Weaver, it’s the development of culture that’s responsible for subduing the environment’s effect on Neanderthals and modern humans. It’s probably not so much a case of one or the other – positive natural selection or genetic drift – it’s likely a combination of the two in varying degrees. With positive natural selection less dominant, it’s again more likely that the cranial differences are due to genetic drift. So ultimately, what he’s saying is that modern humans can chalk up their dashing good looks to chance!

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Gone Today, Back Tomorrow June 4, 2007

Posted by Mrs Weird Scientist in Genetics, Human Body, Stem Cells, Tough Stuff.

Hair follicles, that is. Scientists used to think that once a person lost their hair follicles and went bald, the follicles could never be replaced again. Nope. According to a study by some very curious scientists at the University of Pennsylvania, there’s still hope for your balding dad.

Here’s What Happens

Your head contains thousands of hair follicles and each follicle can grow a single hair. The follicles themselves are actually kinda old because they are produced by an embryo, which is the earliest stage of human development. Scientists used to think that once an embryo had produced follicles, that was it. No more follicles could be made later. So once the follicles were damaged or lost, hairless forever!

This is where a gene comes in to save the day. Your genes are something you inherit from your parents. They are a unique set of instructions that determine the color of your eyes and lots of other traits you have. Scientists at the University of Pennsylvania found a gene called Wnt. This gene not only helps wounds heal, but it can also help make new hair follicles.

The Experiment

So you’re maybe wondering how this new gene can help those damaged hair follicles in your bald dad? Well, lets take a look at what scientists did in the experiment. They removed little bits of the outer skin layer, also called the epidermis, in mice. Remember how I said the Wnt gene helps heal wounds and produce new hair follicles? Well, after that small piece of skin was removed from each mouse, a wound was left.

Now, two really fascinating things happened.

The first thing was that when the wound started to heal, new follicles began to grow. Did the Wnt gene do it alone? No way- something else helped. The second thing is that scientists figured out stem cells were responsible for this growth. These are very special cells found all over your body that can multiply into many more cells. When the scientists removed a little piece of skin from each mouse- creating a wound- this was like a signal for the Wnt gene to get those stem cells to wake up and start working.

But Wait, There’s More

To make sure they really had something that worked, scientists tried to block the Wnt gene. What do you think happened? If you guessed that no new hair follicles were produced, you are right! Without the Wnt gene to activate them, the stem cells didn’t create new hair follicles. And since scientists like to meddle so much, they decided to try increasing the gene’s activity. What now? If you guessed that more hair follicles were produced, you are right again.

Stem Cells

Run That By Me One More Time?

It’s like a series of alarm clocks. The wound wakes up the Wnt gene, which then wakes up the stem cells. Those stem cells can now get busy fixing the wound and creating hair follicles. Block the Wnt gene and the stem cells won’t do their thing. Boost the Wnt gene’s power and the stem cells work overtime.

Is Dad Gonna Grow A Full Head Of Hair?

Maybe one day, but not anytime soon. Scientists still need to figure out how to safely create a wound on a bald spot and then power up the Wnt gene. For now, you can tell dad not to throw out that hairpiece just yet. Remind him it could be worse- he could be losing his teeth.

Photo Credit: George Cotsarelis, University of Pennsylvania, School of Medicine. The blue lines in the picture show copies of cells originating from stem cells. The cells move toward the middle part of the wound to heal it quickly and produce hair follicles. It looks gross but once it has healed, there’s almost no scarring and better yet, there’s hair!

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