Several research teams have worked together to create the most comprehensive cell atlas of the human brain to date and, among other things, identified more than 3,000 types of brain cells. For example, they examined how nerve cells in the brain differ from one another in their functions. A total of 21 studies, which are part of the NIH's "Brain Initiative", are presented in the journals "Science", "Science Advances" and "Science Translational Medicine".
A team led by Kimberly Siletti from the Karolinska Institute in Stockholm examined tissue from 14 human brains. Using a new method, it clarified which RNA sequences were present in the individual brain cells. RNA (ribonucleic acid) serves, among other things, as a transmitter of information from the genetic material in order to produce proteins. Depending on the tasks of cells, the RNA sequences in them differ, from which the researchers were able to derive 3,313 different types of cells. The data set for this work included more than three million brain cells.
In two further studies, a team led by Yang Li from the University of California and one led by Wei Tian from the Salk Institute for Biological Studies examined the epigenetics of individual brain cells. Epigenetic mechanisms determine how often which gene is retrieved from the genome in a cell. Epigenetics is also influenced by the environment, diet and aging. Taken together, these three studies have created a brain cell atlas that characterizes individual brain cell types and assigns them to individual brain regions. This atlas is freely accessible to all scientists.
Researchers: Beginning of a new era
"This is truly the beginning of a new era in brain research in which we can better understand how brains develop, age and are affected by disease," said Joseph Ecker of the Salk Institute, who is involved in several of the studies was.
The activities for the brain cell atlas are bundled in the BICCN (Brain Initiative Cell Census Network) project. BICCN now also makes it possible to gain further insights into the human brain, such as how the brains of humans and monkeys differ. This is what a team led by Nikolas Jorstad from the Allen Institute for Brain Science in Seattle did, among others: They examined samples of a brain region that is associated with facial recognition and reading in humans, from adults, chimpanzees, gorillas, rhesus monkeys and Marmosets.
"Only a few hundred genes showed human-specific patterns, suggesting that relatively few cellular and molecular changes clearly define the cerebral cortex structure of the adult human," Jorstad and colleagues summarize their findings.
Discoveries should help develop new therapies
But the researchers are also concerned with advances in human medicine: "Mapping the different cell types in the brain and understanding how they work together will ultimately help us discover new therapies that target individual cell types that are relevant to specific diseases," says Bing Ren from the University of California. Ren is the senior author of the study by Li and colleagues. The scientists were able to link molecular biological aspects of 107 different subtypes of brain cells to a wide range of neuropsychiatric diseases, including schizophrenia, bipolar disorder, Alzheimer's disease and major depression.
Further research concerned the development of the human brain from the early embryonic stage. This research also gave Sten Linnarsson's team from Sweden's Karolinska Institute new insights into glioblastoma, one of the most aggressive brain tumors. The tumor cells are similar to immature stem cells that are trying to form a brain, but in a completely disorganized way. "We observed that these cancer cells activated hundreds of genes specific to them, and it could be interesting to investigate whether there is a potential for finding new therapeutic targets," explained Linnarsson.