Gina Kolata from The New York Times writes about a baffling brain disorder that is linked to a particular type of bacteria living in the gut (Warning: source may be paywalled; alternate source) The new study, published on Wednesday in Nature, is among the first to suggest convincingly that these bacteria may initiate disease in seemingly unrelated organs, and in completely unexpected ways. The researchers studied hereditary cerebral cavernous malformations — blood-filled bubbles that protrude from veins in the brain and can leak blood or burst at any time. When Dr. Mark Kahn, professor of cardiovascular medicine at the University of Pennsylvania’s Perelman School of Medicine, began this work, the microbiome was the last thing on his mind. Dr. Kahn and his colleagues studied cerebral cavernous malformations as part of a larger effort to understand the development and function of blood vessels. Three genes have been linked to the disorder, and Dr. Kahn and his colleagues tried to figure out what these mutations really do. The scientists were able to mimic the condition in mice by deleting a gene that is mutated in many patients. A year ago, the scientists moved to a new building, and something unexpected happened. The experimental mice stopped developing the brain malformations. Dr. Kahn’s student, Alan T. Tang, had been deleting the gene by injecting a drug into the abdomens of the mice. Sometimes a mouse would get an infection that would lead to an abscess, and bacteria leaked from the gut into the blood. In the new building, only those mice still developed the brain defect. The other gene-deleted mice did not. He and his colleagues finally identified the culprit: Gram-negative bacteria, named for the way they stain, that carry a molecule in their cell walls, a lipopolysaccharide. Without a functioning gene, the lipopolysaccharide can signal veins in the brain to form blood bubbles.
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