One Brain, Many Genomes:
Genomic variability between single neurons in health and disease

Christopher Walsh, MD PhD

Chief, Division of Genetics and Genomics, Children's Hospital Boston; Investigator, Howard Hughes Medical Institute; Bullard Professor, Pediatrics and Neurology, Harvard Medical School

As soon as the fertilized egg divides for the first time, the genomes of cells start accumulating spontaneous mutations, due to errors in DNA replication or other causes.  In principle, every cell in the body has its own distinct genome defined by spontaneous mutations.  Though the role of spontaneous, clonal mutations in cancer is well known, more recently some brain diseases have been found to reflect similar types of mutations, while genomic variability has been suggested to have potential roles in normal brain as well.