A grant from the 2009 federal stimulus package has made it possible for a large team of researchers specializing in various fields of medicine and technology to map the fetal brain as its never been done before. Ed Lein calls the map a "pretty big leap," as "basically, there was no information of this sort prior to this project."
Lein, an investigator for the Allen Institute for Brain Science in Seattle, Washington, played a key role in development of the map. This mapping of "a remarkable process" controlled by our genes is part of the BrainSpan Atlas of the Developing Human Brain project.
Scientists often describe the human brain as the most complex object in the universe. It starts with just one single cell and, in nine short months, grows to 80+ billion cells that allow us to think, see, feel, love, sing, dance, and remember.
Tens of thousands of tiny tissue samples were scrutinized during the study to determine which genes were turned on and which were turned off at the midpoint of gestation. It's at this stage of pregnancy that brain development kicks into high gear. The tissue samples came from four aborted fetuses, in keeping with government-sanctioned protocols for scientific study.
By learning which cells were turned on or off, the researchers could determine which types of cells were forming at specific points in the brain and what they were doing there. A simplistic example of gene expression (on or off) is that a brown-eyed baby would have genes for mom's blue eyes turned off but genes for daddy's brown eyes turned on.
One discovery sure to prove invaluable in future studies is identification of the specific regions of the brain where disorders such as autism and schizophrenia originate. Genes associated with autism were concentrated in the cells of the brain's neocortex, suggesting the disorder originates long before a baby is born. Other genes governing other disorders were discovered at various points in the fetal brain map, even for conditions that usually don't become symptomatic until early adulthood, such as schizophrenia.
Another surprising discovery is that the human brain is actually a lot more different from a mouse brain than previously understood. Mice are often used in medical experiments because their brains are thought to respond in much the same way as the human brain and their much-shorter lifespan allows the study of multi-generations in less time than studying human generations. This finding of brain differences may explain why some medications work effectively in mice but not in people.
Dr. Thomas Insel, director of the National Institute of Mental Health, describes the "enormous surprise" discovery that gene expression in the fetal brain is nothing like that of the adult brain. "It's almost as if the fetal brain is a different organ altogether."
The fetal brain map is available for researchers everywhere to use.
Source: Lein, Ed S, et al. "Transcriptional landscape of the prenatal human brain." Nature. Nature Publishing Group / Macmillan Publishers Limited. Apr 2, 2014. Web. Apr 15, 2014.