There is a growing body of evidence that what happens to us early in life—beginning before birth and continuing into childhood—has important consequences on our general and mental health. Brain researchers have been intensifying the search to understand how traumas experienced by the mother during pregnancy, for instance, can increase the child’s risk of having an anxiety disorder, or even schizophrenia.
Basic researchers like Denis Jabaudon, M.D., Ph.D., who received a NARSAD Young Investigator Grant in 2010 and just a few weeks ago received the Foundation’s 2014 Freedman Prize for Exceptional Basic Research by a Young Investigator, are piecing together what is actually happening in the developing brain as the highly vulnerable fetus, and later infant, is getting its first “taste” of sensory experience.
With colleagues at the University of Geneva, Switzerland, Dr. Jabaudon studies the genetic mechanisms that control the identity of a wide diversity of neurons that make up the cerebral cortex, the brain’s center of higher cognitive processes. In an elaborate choreography during development, these neurons assemble to form circuits. In earlier work, Dr. Jabaudon had shown that neurons and the circuits they form are not only more plastic than was previously thought, but can be manipulated to reverse-engineer specific functional circuits well after neuronal identity has been assigned.
This work had offered a proof-of-principle for the postnatal re-engineering of neuronal circuits in vivo. Harnessing this instructive potential of genes may have clinical application by enabling the repair or even prevention of the mis-wiring of circuits that underlies a variety of brain disorders.
In his most recent experiments reported July 24th in Nature, Dr. Jabaudon and colleagues take this work a step further, by rewiring the input to neurons in a part of the brain called the somatosensory cortex, the main sensory receptive area for the sense of touch. Working in mice, their experiments showed that the identity of target neurons in this cortical area was reassigned to correspond to their newly-acquired input, on a molecular, circuit, and even behavioral level.
“Our study shows that the identity of cortical neurons and the circuits they form is significantly determined by sensory input, and identifies the molecular mechanisms underlying this effect,” says Dr. Jabaudon. “This means that environmental factors strongly influence neuronal gene expression and circuit formation during development. This identifies a path through which adverse environmental conditions could lead to abnormal gene expression and circuit mis-wiring in neurodevelopmental and psychiatric disorders.”