Scientists have long puzzled over the vast complexity of the human brain. Now, researchers from across the world have mapped its cellular make up and discovered that there are over 3,000 cell types in the human brain, including hundreds they didn’t know existed.
Speaking to BBC Science Focus, Dr Ed Lein, senior investigator and neuroscientist at the Allen Institute for Brain Science, said: “The brain is an astonishingly complex cellular organ … and we can now really define and map these cell types across it.”
Previous studies had only mapped the brain cell types of particular regions in the cortex (the outermost part of the brain). These studies found over 100 different brain cell types.
The new research has expanded that mapping to almost 100 regions across the entire human brain – and found thousands of different brain cells.
For many parts of the brain, no-one has ever seen this level of complexity and variety until now. The researchers were surprised to discover that even the oldest parts of the brain (in evolutionary terms), which were previously thought to be very simple, are in fact highly complex.
In the study, scientists at Allen Institute for Brain Science used a technique known as single-cell transcriptomics, which involves studying all the genes switched on in individual brain cell’s DNA. They analysed post-mortem tissues from brains donated to science, and healthy living tissue donated by brain surgery patients.
The study is part of a huge project to catalogue the size and complexity of the human brain, and is one of a suite of 21 papers released simultaneously in Science, Science Advances and Science Translational Medicine.
One of the other studies, also led by the Allen Institute, found that the connections between the 3,000 brain cell types are crucial to making us unique individuals. Although “we all share a common blueprint and set of building blocks,” said Lein, there is “variation in how those blocks are put together and the properties of those blocks that make us unique as individuals.”
In a press release, Lein described the joint discoveries as “a pivotal moment in neuroscience”. The findings will help to create more comprehensive atlases of the entire human brain, as well as for brains of other primates. These could improve our understanding of brain diseases and disorders, and our ability to treat them.
“This is very much like the early stages of the Human Genome Project,” Lein added to BBC Science Focus. “We have now begun that journey.”
About our expert
Dr Ed Lein is the Senior Investigator and neuroscientist at the Allen Institute for Brain Science. His research has been published in PLOS Biology, Nature Biotechnology, and Nature Reviews Genetics.
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