Somatic mosaicism, the phenomenon whereby not all cells of the human body have an identical DNA sequence, occurs as part of the normal developmental process. Although there is increasing evidence of somatic mosaicism in the brain, the extent of such variation and its functional significance in normal brain development and in psychiatric disorders remain poorly understood. Identifying the architecture of genetic perturbations in somatic cells of normal and diseased brains may provide new insights into genetic susceptibility of complex psychiatric disorders.

The National Institute of Mental Health (NIMH) has funded the Brain Somatic Mosaicism Network (BSMN) program with the goal of accelerating the discovery of a range of somatic genomic variations across human brain cell and tissue types and elucidating its role in the development of mental illnesses. The BSMN is a multi-site effort comprised of six project nodes that will use advances in DNA sequencing, single-cell genomics, computational biology, and genome engineering to determine the extent of somatic mosaicism in normal brains and neuropsychiatric disorders.