Movement is a very complex process involving millions of neurons in different parts of the brain, with the motor cortex playing a central role. The signals are then sent from the brain to the spinal cord and then to the muscles. To increase knowledge of how this works, the different cell types in the kinetochore cortex of humans, mice, and silk monkeys have now been identified to the smallest detail.
Behind this initiative is a large consortium of hundreds of researchers brought together in the BRAIN Initiative Cell Census Network, BICCN, which was launched by the US National Institutes of Health (NIH) in 2017.
The cell atlas is described in a special package containing a total of 17 scientific articles published in Nature, including a summary high-level analysis describing the entire atlas. Researchers at Karolinska Institutet contributed data on the human brain to the interspecific evolutionary comparison, led by Allen Institute for Brain Sciences, which was an important part of building the cell atlas.
Millions of neurons in the motor cortex
The atlas is freely available and represents the most comprehensive and detailed data collection to date of any part of the mammalian brain. Researchers have divided the millions of neurons and other types of brain cells found in the motor cortex into different categories. Many different methods have been used to measure a variety of properties of individual cells, including the full set of genes that the cell activates, the three-dimensional shape of the cell, its electrical properties and how the cell communicates with other cells.
To understand how the brain works and what goes wrong when we suffer from disease, we must start by looking at the brain’s most important building blocks, which are cells. Once we create a catalog of all the types of cells that make up our brains together, we can learn more about how they interact with each other in a system, says Sten Linnarsson, a professor in the Department of Clinical Biochemistry and Biophysics at Karolinska Institutet, who has co-authored several articles.
Similar cell types control the movements of different mammals
In comparing mice, humans, and silkworms, the researchers found that most types of cells in the kinetochore have similar analogs in all three types of mammals. What varied between species was mainly the proportions of cells, their shapes and electrical properties as well as individual genes being turned on and off. The researchers also studied in detail the electrical signals sent by human Betz cells, the large nerve cells that connect to the spinal cord and which ALS attacks.
Mapping the motor cortex could lead to a better understanding of diseases where the neurons that control our movements are under attack, such as ALS. But the project does not end here. Together, we will now continue to map other regions of the brain until we have a complete cell atlas of the entire human brain, says Steen Lenarson.
The research is primarily funded by the National Institute of Mental Health (NIMH) in the United States, which is part of the National Institutes of Health. Potential conflicts of interest are listed in scholarly articles.
Scientific articles in which KI researchers participate:
Leading Paper: Multimodal cell count and atlas of the mammalian primary motor cortex. Brain Initiative Cell Count Network (BICCN), temper nature, online October 6, 2021.
Evolutionary comparison between species: Comparative cytological analysis of the motor cortex in humans, monkeys and mice. Trygve E. Bakken et al, Nature, online Oct 6, 2021, Available here.
Sten Linnarsson, Professor, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, [email protected]
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