Category: Genetic disorders

Will we ever correct diseases before birth?

By Ed Yong | April 25, 2012 9:00 am

Here’s the sixth piece from my new BBC column

Every year, millions of people are born with debilitating genetic disorders, a result of inheriting just one faulty gene from their parents. They may have been dealt a dud genetic hand, but they do not have to stick with it. With the power of modern genetics, scientists are developing ways of editing these genetic errors and reversing the course of many hard-to-treat diseases.

These gene therapies exploit the abilities of viruses – biological machines that are already superb at penetrating cells and importing genes. By removing their ability to reproduce, and loading them with the genes of our choice, we can transform viruses from causes of disease into vectors for cures.

After a few shaky starts, some of these approaches are beginning to hit their stride. Thirteen children with SCID, an immune disorder that leaves people fatally vulnerable to infections, now have working immune systems. Several British patients with haemophilia, which prevents their blood from clotting properly, can now produce a clotting protein called factor IX, which they once had to inject. A British man and three Americans with inherited forms of progressive blindness can see again.

It is still early days as far as trumpeting gene therapy cures are concerned, but even if they do succeed there is still one significant limitation that cannot be overlooked. Treating adults and children in this way will do for some disorders, but genetic disorders cause irreparable organ damage, or even death, very early. “With some of the diseases that we look at, five years old is too late. Sometimes, you don’t get to the age of five,” says Simon Waddington from University College London. “Every single one is a little bit niche but when you list them all out, there’s quite a lot of them.”

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Jumping genes mobilise in the brains of people with Rett syndrome

By Ed Yong | November 17, 2010 1:00 pm

MECP2_L1In the brain of a baby, developing in her mother’s womb, a horde of DNA is on the move. They copy themselves and paste the duplicates into different parts of the genome. They are legion. They have been released from the shackles that normally bind them. And in a year’s time, the baby that they’re running amok in will develop the classic symptoms of the debilitating brain disorder known as Rett syndrome.

Children with Rett syndrome – they’re almost all girls – appear normal for about a year before their development is spectacularly derailed. The neurons in their brain fail to develop properly. They lose control of their hands. Most will never speak and at least half cannot walk on their own. Digestive problems, breathing difficulties and seizure are common. They will depend on their loved ones for the rest of their lives.

In most cases, this panoply of problems are all caused by faults in a single gene called MECP2, nestled within the X chromosome. MECP2 is a genetic gag – it silences other genes in a way that’s essential for producing healthy, mature neurons. But Alysson Muotri and Maria Carol Marchetto – a husband and wife team – have found that MECP2 also has another role. It acts like a warden, restraining a mafia of mobile genes called LINE-1 sequences or L1.

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How I got my genes tested, and the birth of Science Writer Disease Risk Top Trumps

By Ed Yong | July 21, 2010 9:00 am

23andmekit

Thanks to genetic testing, I now know that If it were biologically possible to have a baby with Mark Henderson, Science Editor of the Times, that baby would be certain to have wet earwax. And he or she would definitely not have cystic fibrosis. Science!

This is all in aid of a session at the UK Conference of Science Journalists exploring the world of genetic testing, hosted by Mark, Daniel Macarthur from Genomes Unzipped and others. As part of the session, various journalists were offered the chance to get their genes tested for free by one of the three leading companies providing such services. I had a brief chat to Daniel about it, got his recommendations, and signed up. Four days later, a testing kit from 23andme arrived on my desk. I knew that 23andme had recently swapped some samples in a technical blunder but after reading Daniel’s blog, I was convinced that it was unlikely to happen again. If it did, I would enjoy finding out that I was secretly a black woman.

An hour later, I had delivered a dollop of my finest sputum into the tube they provided… and realised that I was only about a third of the way up to the fill-line. Doing this in the middle of the office was not a smart move. Ten further minutes later, and to a crescendo of laughter from my colleagues, the tube was full, sealed in a biohazard bag (I try not to take this as an indictment of my breath) and sealed in a Fed-ex envelope.  Four weeks later, the results arrived. The whole process couldn’t have been simpler.

In fact, it was perhaps too easy. Signing up to the 23andme site, verifying the code on my testing kit and preparing the sample took little more than an hour. I had to read and agree to documents that reassured me about the privacy of my information and provide consent to analyse my samples. The same documents warn about the possible psychological consequences of finding out your data and the limtiations of the resulting information (more on these later; meanwhile, I’ve uploaded the full consent form to Posterous so you can see it for yourself). Nonetheless, I was well aware of these risks. I could have found out that I have substantially high odds of developing life-threatening diseases. I could have discovered that I’m not actually related to my parents. This is not a bottle one can re-cork.

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