Aging brains acquire marrow-derived microglia via somatic mutations

A new study uses accumulated somatic mutations to trace human microglial origins, revealing that marrow-derived cells infiltrate aging brains, resemble microglia, and can become a large fraction of the microglial pool; cohort data also show a protective association between clonal hematopoiesis and Alzheimer's disease, suggesting aging brains recruit marrow-derived myeloid cells into the microglial population.