Word: mitochondria
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...working on mitochondrial disease back in the '80s," says Shoffner, "people were still arguing over whether it even existed." Nobody is arguing about that anymore. In fact, doctors have now identified hundreds of different subtypes of the disorder. What they all have in common is a malfunction of the mitochondria--tiny substructures, or organelles, found inside every cell in the body. Their job is to convert food into a chemical called ATP that cells use for energy. When they go bad, all sorts of havoc is wreaked on the body. Depending on which types of cells are affected, mitochondrial disease...
Officially, as many as 2 million Americans suffer from mitochondrial disease. But because defects in the mitochondria may underlie an astonishing range of very familiar illnesses, researchers are beginning to suspect that the real number is vastly higher. In the past few weeks alone, reports have come out in Cell, Nature and the Journal of Neuroscience implicating the mitochondria as factors in diseases such as Alzheimer's and Parkinson's. Indeed, says Dr. Vamsi Mootha, a Harvard Medical School researcher who won a MacArthur Foundation "genius" grant in 2004 for his work on mitochondria, "it looks like they're really...
Exactly what role mitochondria play in these illnesses is still unclear. It's not even certain whether mitochondrial breakdowns are the cause or the effect of disease--although researchers suspect it's often a little of both. As mitochondria process food into energy, they create free radicals--highly reactive oxygen ions that can cause damage to proteins. Many experts believe that as cells age, this damage accumulates, weakening the mitochondria irrevocably and doing harm to specific organs--or, more generally, to the whole body. There's no smoking gun yet, says Mootha, but there's some tantalizing evidence...
...known mitochondrial diseases, though, it's clearly a genetic abnormality that almost always sets things off. Mitochondria are different from the rest of the cell in that they have their own DNA, inherited directly from the mother (with no input from the father) that's entirely separate from the DNA in the nucleus. Evolutionary biologists suspect, in fact, that these organelles started out as independent bacteria that were absorbed long ago into cells and harnessed as energy factories...
Even with the controversy raging over his stem-cell paper, Hwang could have forestalled some of the questions about Snuppy if he had offered one additional bit of confirming proof in his original paper in Nature. That piece of critical evidence comes from the animals' mitochondria, tiny energy-producing structures within each cell. While most of a mammal's DNA resides in the nucleus, there's also some in the mitochondria. (Nuclear DNA forms the animal's basic genetic blueprint; mitochondrial DNA contains instructions for making proteins involved in various metabolic functions within the cell...