Prenatal pruning of neurons with copy number variants; and more

Pruning method: Many neurons in the prenatal brain are rife with copy number variants, most of which are eliminated before birth or shortly thereafter, a new study reports. Investigators conducted whole-genome sequencing in neurons from human postmortem brains from before birth to older than 90 years. On average, 25 percent of prenatal cortical neurons carried copy number variants, but the number of neurons with aberrant genomes dropped more than fourfold after birth. Neurons with high numbers of copy number variants also showed altered expression of synaptic genes, suggesting that these cells failed to form connections—and ended up targeted for removal.