Tuesday, 30 August 2011

The human genome: we’re just getting started

When the human genome was sequenced over a decade ago, it was a momentous scientific breakthrough. The human genome is enormous. The genome is about 3 billion DNA bases lined up one after the other along chromosomes (which are conveniently broken up into 23 parts). It contains all our genes as well as all the information about when those genes should be switched on and off. Many diseases are caused by genetic changes, so by comparing your or my genome to the average we should be able to see what diseases await us. It was as though a crystal ball had been dropped into our laps. All we had to do was look into it and see everything from our next colds to our eventual deaths. Really, by now there should be an iPhone App for it. So what happened?

As with many scientific discoveries, the sequencing of the human genome was over-hyped. It was a scientific breakthrough, but not a medical one. It takes a long time for scientific discoveries to become medicines that affect the lives of patients. A decade or more usually passes from the time a treatment is thought up to the time the first patient is treated, and most drugs don’t work and therefore never make it into patients at all. One of the most important things that scientists have used the genome data for is genome-wide association studies. In these studies the genomes of healthy people are compared with the genomes of people with diseases like heart disease, diabetes, cancer and autoimmunity. Scientists have found a number of mutations in people with those diseases, but knowing that a mutation is there is only the first step. The next steps are to see what that mutation does, try to develop drugs to fix the problem, and then see if those drugs are safe. These discoveries will take time. But without the genome data there in the first place, we wouldn’t even have a starting point. There are over 500 genetic diseases from cystic fibrosis to hemophilia. We can test for most of these. Now we need to develop ways to treat them.

Another important change has occurred over the last ten years. DNA sequencing has become cheaper and faster. Since most genomes differ by 1-3%, we need to have a better idea of what “normal” is. The only way to do this is to collect a bunch of normal samples and see how they differ from one another. The Human Genome Project, the publicly-funded effort to sequence the human genome, cost about £1.5 billion and took 11 years to complete. Sequencing the genome now would cost closer to £15,000 and take a couple of months. The X-prize Foundation currently has a $10 million prize for anyone who can sequence 100 human genomes in 10 days for less than $10,000 per genome. We’re not there yet, but we’re not far off. The competitive spirit has been part of sequencers’ ethos since the very beginning. The race to publish the genome itself was nail-biting, including a photofinish between the Human Genome Project and a splinter biotech company founded by a maverick scientist out to show us all how it should be done. Who says scientists are boring?

Anyone with internet access and a penchant for staring at repetitive things can look at the human genome for themselves ( http://genome.ucsc.edu/ has a good browser for this). The Human Genome Project and the scientific journals have been instrumental in ensuring that all the data is publically available. Before the human genome it was difficult to convince another scientist to show you his data unless you showed her yours. Anyone with little to show was left in the dark. Having easy access to data means that scientific discoveries happen faster. Genomes are being sequenced faster and faster, and that data is available to anyone who wants it. DIY biologists are starting up companies in their garages. Making DNA is becoming faster and cheaper. Bacteria with synthetic genomes have been created. Biology is accelerating.

As Isaac Newton once said, “If I have seen further it is only by standing on the shoulders of giants”. The sequencing of the first human genome was a gigantic accomplishment. It will take some time before we can use this information to improve our health, but as discoveries start happening faster and faster it’s only a matter of time before the era of genetic medicine is upon us. These are exciting times, and they will yield exciting results. One day we will be able to sequence a person’s genome, know what diseases they’re likely to get, and then prevent those diseases from happening. It will, however, take time. Patience, patients.

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