A bone-marrow transplant can treat a mouse version of Rett syndrome, a severe autism spectrum disorder that affects roughly 1 in 10,000-20,000 girls born worldwide (boys with the disease typically die within a few weeks of birth).

The findings, published today in Nature, suggest that brain-dwelling immune cells called microglia are defective in Rett syndrome. The authors say their findings also raise the possibility that bone-marrow transplants or other means of boosting the brain's immune cells could help treat the disease.