Overview
- The Nature paper published 28 October 2026 reports that about 25.9% of sampled prenatal cortical neurons carried large copy number variants while roughly 6.2% of neurons after birth did, indicating a sharp drop around birth.
- Researchers used a new, lower-cost single-cell whole-genome method to lightly sequence 1,526 neurons from 16 individuals, validated findings with deeper sequencing of 831 neurons from 12 individuals, and profiled DNA and RNA in 44,861 single cells to map changes.
- Cells with widespread copy number variants showed abnormal expression of genes for making and maintaining synapses, a pattern consistent with those neurons failing to form connections and being eliminated by synaptic competition.
- The team found that some genetically abnormal neurons persist into adulthood at much lower rates, and the authors stress the study is observational and are now testing whether this elimination process is altered in autism, epilepsy, and neurodegenerative disorders.
- The finding builds on known developmental pruning and IVF evidence of early mosaicism and could shift research toward protecting or detecting disrupted perinatal quality control as a route to prevent some brain disorders.