Two related studies revealed gene activity in the brains of people of different genders and ethnicities, from fetal development to old age. The accomplishment provides a broad foundation for understanding both normal brain development and what goes awry in mental disorders. Messenger RNAs, or transcripts, are transient copies of genes that carry instructions to the protein-making machinery within cells. Transcripts are made, or “expressed,” in patterns that are influenced by the approximately 1.5 million DNA variations unique to each of us. Researchers led a broad survey to find which genes are active in different areas in the brain at different stages of life and they found that different sets of genes are expressed during prenatal development, infancy and childhood. Three-fourths of genes change expression levels immediately after birth, with most decreasing. Gene expression gradually declines from there, eventually leveling off in middle age. It then surges again as the brain ages in the last decades of life. Individual genetic variations are profoundly linked to expression patterns. However, despite differences in the genetic code across individuals and ethnicities, the transcriptomes—the complete set of expressed transcripts—of human brains are generally similar.
Over 90% of the genes expressed in the brain are differentially regulated across brain regions and/or over developmental periods. Brain location and timing, the researchers found, affect gene expression far more than gender, ethnicity or individual variation.
