The Stuff of Nightmares
Fibrodysplasia ossificans progressiva, or F.O.P., is the weirdest, and most horrifying, condition that I've ever seen. Fortunately, researchers at the University of Pennsylvania think that they are on the verge of a breakthrough.
But after examining blood samples from five families in the United States, Britain, South Korea and Brazil, Dr. Kaplan and Eileen Shore, a colleague, found that the rampant bone growth begins with a tiny error in the nucleotide sequence of a gene that serves as a blueprint for a protein called ACVR1.
When expressed on the surface of cells, ACVR1 receives signals from a molecule called bone morphogenetic protein. The misconfigured ACVR1 protein is activated when it should not be, Dr. Kaplan theorizes, effectively forcing adult stem cells to become bone cells.
As a result, stem cells recruited to the site of a muscular injury differentiate only into bone. For patients with F.O.P., even small wounds, like minor falls or vaccinations, can bring on uncontrolled explosions of new bone.
"It's like a runaway factory for bone that just won't stop," said Dr. Kaplan.
I've been reading Richard Dawkins' River Out of Eden. (Contrary to what a lot of people have said, I find this book really fascinating.) Here's what he says:
When an embryo begins, a single cell, the fertilized egg, divides into two; each of the two divides into four; each of the four divides to make eight, and so on. It takes only a few dozen generations to work the cell numbers up into the trillions, such is the power of exponential division. But, if this were all there was to it, the trillions of cells would all be the same. How, instead, do they differentiate (to use the technical term) into liver cells, kidney cells, muscle cells and so on, each with different genes turned on and different enzymes active?
Yes, how?
Although the egg looks like a sphere, it actually has polarity in its internal chemistry. It has a top and a bottom and, in many cases, a front and a rear (and therefore also a left and a right side) as well. These polarities show themselves in the form of gradients of chemicals. Concentrations of some chemicals teadily increase as you move from front to rear, others as you move from top to bottom. These early gradients are pretty simple, but they are enough to form the first stage in a bootstrapping [refers to the patterned toggling switches in old, paper- or card-fed computers] operation.
For those of you who love computer programming, River Out of Eden is the book for you. My curiosity about this book was piqued while listening to a talk by Dawkins online ("Selfish Gene, 30 Years Later") in which he referred to genetics as digital. Huh? Well, it makes sense. Read it!
But after examining blood samples from five families in the United States, Britain, South Korea and Brazil, Dr. Kaplan and Eileen Shore, a colleague, found that the rampant bone growth begins with a tiny error in the nucleotide sequence of a gene that serves as a blueprint for a protein called ACVR1.
When expressed on the surface of cells, ACVR1 receives signals from a molecule called bone morphogenetic protein. The misconfigured ACVR1 protein is activated when it should not be, Dr. Kaplan theorizes, effectively forcing adult stem cells to become bone cells.
As a result, stem cells recruited to the site of a muscular injury differentiate only into bone. For patients with F.O.P., even small wounds, like minor falls or vaccinations, can bring on uncontrolled explosions of new bone.
"It's like a runaway factory for bone that just won't stop," said Dr. Kaplan.
I've been reading Richard Dawkins' River Out of Eden. (Contrary to what a lot of people have said, I find this book really fascinating.) Here's what he says:
When an embryo begins, a single cell, the fertilized egg, divides into two; each of the two divides into four; each of the four divides to make eight, and so on. It takes only a few dozen generations to work the cell numbers up into the trillions, such is the power of exponential division. But, if this were all there was to it, the trillions of cells would all be the same. How, instead, do they differentiate (to use the technical term) into liver cells, kidney cells, muscle cells and so on, each with different genes turned on and different enzymes active?
Yes, how?
Although the egg looks like a sphere, it actually has polarity in its internal chemistry. It has a top and a bottom and, in many cases, a front and a rear (and therefore also a left and a right side) as well. These polarities show themselves in the form of gradients of chemicals. Concentrations of some chemicals teadily increase as you move from front to rear, others as you move from top to bottom. These early gradients are pretty simple, but they are enough to form the first stage in a bootstrapping [refers to the patterned toggling switches in old, paper- or card-fed computers] operation.
For those of you who love computer programming, River Out of Eden is the book for you. My curiosity about this book was piqued while listening to a talk by Dawkins online ("Selfish Gene, 30 Years Later") in which he referred to genetics as digital. Huh? Well, it makes sense. Read it!
posted by Kristine | Monday, May 15, 2006
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