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October 2012 Archives

A Giant Leap for 'Three Parent Embryos'

Mitochondria are the powerhouses of the cell; their function is to produce energy. (See the orange-colored structures in the figure.) These tiny cellular organs also contain a trace amount of DNA (mitochondrial DNA or mtDNA), which encodes various enzymes used in energy production and RNA molecules for protein synthesis.

Since sperm do not contribute any mitochondria to a fertilized egg, all of the mitochondria a cell contains came from the mother. Also, because mitochondria contain DNA, they are susceptible to mutations, and hence, genetic disease. Mitochondrial diseases tend to affect cells which use a lot of energy, such as muscles and neurons, and the severity of the disease depends on the type of mutation and the number of mitochondria affected. 

If a woman has a mitochondrial disease, she will almost certainly pass it on to her children. But, scientists at the Oregon Health & Science University have shown that a gene therapy technique may be able to prevent the transmission of mitochondrial disease.

Researchers acquired eggs from healthy human donors and then performed reciprocal "spindle transfer." This means they swapped the egg's nuclei (the structures which contain most of a cell's DNA -- the purple blob in the picture). In other words, the nucleus of Egg #1 was transferred to Egg #2, and the nucleus from Egg #2 was transferred to Egg #1. (Note that the mitochondria were left behind.) Following that, the cells were fertilized with sperm and their fate was monitored.

Out of 64 fertilized eggs, 19 developed into blastocysts (early-stage embryos). The researchers were able to derive embryonic stem cells from some of these blastocysts.

Also, the researchers followed up on a previous experiment in which they produced monkey offspring using this "spindle transfer" procedure. The monkeys were completely healthy.

This study is what is known as a "proof-of-concept." Although the researchers used healthy human eggs and monkeys, they showed that it is theoretically possible to transfer a nucleus out of an egg with mutated mitochondria into a new egg that contains healthy mitochondria. From there, fertilization can yield a healthy blastocyst, which can then be implanted into the uterus to produce a healthy baby.

Although this technique shouldn't be controversial, it almost certainly will be. The resulting blastocysts have already been called "three parent embryos," much to the chagrin of scientists. While this is technically true, it should be pointed out that the DNA from the "third parent" (which comes from the healthy mitochondria) is miniscule (around 16k DNA base pairs) compared to the much larger amount of DNA contained in the nucleus (6 billion DNA base pairs in the diploid genome).

This technique, once perfected, will prevent genetic disease being transmitted via mitochondrial DNA. However, it may also keep bioethicists and lawyers busy for a long time.

Source: Masahito Tachibana et al. "Towards germline gene therapy of inherited mitochondrial diseases." Nature 490 (7421). 2012. doi:10.1038/nature11647

(Image: Typical animal cell via Shutterstock)
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October 2012 Archives

Sen. Tom Coburn (R-OK) is a medical doctor and notorious budget hawk. (His colleagues call him "Dr. No" because he likes to block legislation.) Annually, he releases a list of what he perceives to be examples of wasteful government spending. In an era where American debt is $16 trillion, the federal government could probably use a few more people like him.

473px-Tom_Coburn_official_portrait_112th_Congress.jpgEven James Bond couldn't defeat this Dr. No. (Photo: Wikimedia/U.S. Senate)

Being a medical doctor, he's obviously an intelligent man who understands the benefits of science. Yet, in his annual list of government waste projects, Coburn often mocks what sounds like ridiculous scientific research.

Now, science is certainly not immune to waste. Some research (often from the social sciences) isn't worth funding. However, just because research sounds funny doesn't mean it is worthless.

A recent story on Fox News's Special Report uncritically repeated Coburn's claims without examining them. (See embedded video clip at the bottom of this post.) So, let's take a closer look at the three "wasteful" research projects that were highlighted by the report.

Fox News first went after:

...a $325,000 grant to build Robosquirrel -- a robotic rodent designed to test the interaction between a live rattlesnake and a robot squirrel.
That is technically true, but it distorts the purpose of the research. The scientists were examining animal behavior and predator-prey relationships, which is a legitimate field of inquiry. They wanted to know how rattlesnakes respond to squirrel tail-waving (called "flagging" behavior). Obviously, this research can't be done with a real squirrel because, as Samuel Kenyon on Science 2.0 asks, "How can you isolate and test individual animal signal components and the specific responses they elicit?" So they built a robot that looked like a squirrel and tested that on rattlesnakes.

Next on the chopping block:

Although NASA has no plans or budget for manned spaceflight to Mars, the agency spent nearly a million dollars developing the Mars menu -- an effort to come up with a variety of foods that humans could eat if they were on Mars.
This statement is false. NASA absolutely has plans to go to Mars. In August, NASA Administrator Charles Bolden said that the U.S. would go to Mars in the 2030s with an international team. NASA also plans a pit stop on an asteroid by 2025. Obviously, astronauts will need something to eat other than freeze-dried ice cream.

Finally, Fox News criticized:

...the nearly $700,000 grant for development of a musical about global warming. When it opened in Kansas City, a reviewer said he learned nothing new about the topic, that the songs sounded like 'Wikipedia entries set to music,' and that the performance included flying monkey poop.
Okay, Fox News and Coburn have a point here. That's absurd. The National Science Foundation (NSF) has no business funding musicals, even ones about science. Whichever bureaucrat is responsible for this decision should be reprimanded.

Two lessons should be taken from this. First, just because science sounds silly doesn't mean it is worthless. In fact, often the opposite is the case. Second, while it's fun to complain about politicians who waste our money, it is actually unelected bureaucrats who make most of the decisions. Congress simply grants organizations like the NSF a huge chunk of money, and bureaucrats decide how to dole it out (using a process called "merit review.")

If you don't like how the NSF is spending your money, sadly, there isn't much you (or any politician) can do about it. Hiring and firing bureaucrats is a monumental task in and of itself.

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October 2012 Archives

Mad Scientists of the Modern Age: Barry Marshall

Think that mad scientists are confined only to the literary world? Think again. The annals of history are littered with kooky researchers and batty experiments, and many of their stories actually outdo their fictitious counterparts.

This week, Newton Blog tells the tales of some of the past century's most loopy scientists, and recounts their surprisingly profound contributions to modern knowledge. Today, we conclude our series with "Barry Marshall: Guinea Pig for Microbiology.

Peptic ulcers are painful sores which develop in the stomach (gastric ulcers) or upper small intestine (duodenal ulcer). As the mucosal layer which lines the digestive tract erodes away, the underlying tissue is left exposed to stomach acids. This causes extreme pain, and if left untreated, can cause bleeding, other health complications, and possibly death.

For decades, the medical community believed ulcers were caused by stress, too much stomach acid and poor lifestyle choices (diet, smoking, etc). But then along came an Australian medical doctor, Barry Marshall, who had a radical new idea: Ulcers are caused by an infectious microorganism. EMpylori.jpg

In an interview with Discover Magazine, Marshall explained his incredibly difficult uphill battle. Not only was there no incentive to find a cure for ulcers (because antacids produced by pharmaceutical companies were very profitable, and since they didn't cure ulcers, the patients taking them remained dutiful customers for life), but the medical community was skeptical, as well. He also didn't have any good animal models to work with.

So, he did what any good "mad" scientist would do: He experimented on himself.

How did he do this? In the words of Dr. Marshall (from the Discover interview):

I had a patient with gastritis [stomach inflammation and the precursor to an ulcer]. I got the bacteria and cultured them, then worked out which antibiotics could kill his infection in the lab--in this case, bismuth plus metronidazole. I treated the patient and did an endoscopy to make sure his infection was gone. After that I swizzled the organisms around in a cloudy broth and drank it the next morning.
Marshall became ill and vomited, and after several days, just like his patient, he developed gastritis. When his stomach was examined, the guilty bacterium, called Helicobacter pylori, was present. Essentially, he fulfilled Koch's postulates (which is a microbiological process for determining infectious disease etiology) for gastritis, using himself as a guinea pig.

Eventually, the scientific and medical establishments came around to seeing things his way. In 2005, he won the Nobel Prize in physiology, and today, he is something of a legend in the microbiology community.

It is worth pointing out that H. pylori is a great example of the complicated relationship our bodies have with microbial flora. About half the planet is infected with H. pylori, yet most infections are asymptomatic, meaning that a person can carry the bacterium and never get an ulcer. (Also, H. pylori is genetically diverse, meaning one person's bacteria could be very different from another.) Further complicating the picture is the fact that not all ulcers are caused by H. pylori; indeed, some might be due to stress, and a substantial proportion are caused by overuse of non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen.

Marshall's self-experimentation certainly might classify as "mad," but it's positively sane compared to the behavior of Edward Jenner. Jenner, the "father of immunology," tested his new idea of vaccination on his gardener's son, an 8-year-old child, after which he purposefully exposed him to smallpox virus. Lucky for him, Jenner was right.

Thank goodness for modern-day institutional review boards.

(Image: Helicobacter pylori by Yutaka Tsutsumi via Wikimedia Commons)
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