Wednesday, October 27, 2010

Big genetics

Genetics is all pretty abstract until you find out something about yourself. I only know one thing for sure about my own genome-- I have one copy of the most common mutation for cystic fibrosis. I found this out when Hidden B and I had prenatal screening done about four years ago. The estimated chance of having this mutation is about 5%, so I was unpleasantly surprised. I'm defective! (And each of my kids has a 50% chance of being a carrier.)

On the genetics front, big big news today, although I didn't see anything appear in a major outlet. Maybe I missed it-- more likely is that the news was too complex and not attractive enough for the average reader for newspaper editors etc. to assign the story to reporters.

You'll find decent writeups at Nature News and GenomeWeb. A gigantic international research coalition, the 1000 Genomes Project (nearly as many authors as genomes) published a paper in Nature describing how they sequenced about 880 human genomes. I'll leave out the details, which, frankly, are lost on me, but the point of the work was to get a handle on how our DNA varies from one human to the next. An astonishing quote from the abstract:
"On average, each person is found to carry approximately 250 to 300 loss-of-function variants in annotated genes and 50 to 100 variants previously implicated in inherited disorders."
Hoo boy. The authors are saying, in essence: each of us is a factory reject. If we each carry 250-300 genes that ought to work but don't, imagine how much redundancy is built in. If a gene is broken, there are others to compensate for it.

This is why it's so hard to find connections between single genes and diseases. It's why scientists think it's a big deal to find that about 20% of children with eczema have loss-of-function mutations in FLG, the filaggrin gene--because 20% is a large number! (Before I studied molecular biology, I would have thought scientists would only care about mutations that were found in, say, 75% of patients with a given condition.)

And EACH of us has 50-100 variants that put us at higher than average risk for a random grab bag of inherited conditions. Tay-Sachs, anyone? Alzheimer's? If you ask me, there's no need to extend the human lifespan. I don't need to discover how many weird things I might develop if I live past 85.

A much lower-profile item: some journal called Nature Precedings (appears to be a catalog of NIH project summaries) reports an ongoing project of interest to you and me: "Skin Microbiome in Disease States: Atopic Dermatitis and Immunodeficiency." Julia Segre and Heidi Kong at the NIH are studying patients with eczema and two immunodeficient conditions to profile the populations of bacteria and other microbes that live on our eczematous and non-affected skin--and in our nostrils! (A while ago, I don't have the reference, someone discovered that nasty bacteria hide out in our nostrils. So stop picking your nose.)

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