Health

Biology: Researchers create human cell atlas

No.After the entire genome, the researchers map all human cells. For this human cell atlas, three teams have now analyzed more than 500 cell types in 33 tissues in one big step and summarized them into rough maps. The teams present their work in the journal “Science”. Another team analyzed the embryo cells.

With the human cell atlas, you can see in which tissues there are gates for coronal or influenza viruses, says study leader Sarah Teichmann of the British Wellcome Sanger Institute. She is the co-founder of the Human Cell Atlas (HCA) project, which started in 2016 and involves more than 2000 researchers around the world.

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“The atlas tells us which cells have an open door for which viruses. We saw in March that there are receptors for Covid-19 in the nose and the study was published in April 2020. “This showed how important masks are.

Atlas shows where the receptors are located

Furthermore, his team showed that corona viruses also penetrate some cells of the mucous membrane of the mouth and are therefore excreted when speaking. “The cell atlas is like a guide that shows which receptor is in which position.” This is not only important for viruses, but also for drug development.

Work on the cell atlas has been going on for years, but so far mainly single cells, tissues or organs have been cataloged, says Teichmann, who is also director of research at the British University of Cambridge. The cell maps presented in “Science” can be used to show how cells work together between organs.

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“In the immune system, we’ve now learned which T-cells are present in which tissues and so we’ve created a kind of GPS,” says Teichmann. T lymphocytes form different receptors in the spleen compared to other organs. In addition, the analysis techniques have greatly improved. “We are at the point where the technologies are very robust, fast and affordable.”

This isn’t just important for finding receptors. “The healthy tissue stored in the atlas is mainly used as a reference for diseases. It’s easy to see what has changed in a patient, “said Teichmann.

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Just as the Human Genome Project provides a reference for all genes, the human cell atlas is a reference for all cells, said project co-founder Aviv Regev of the Broad Institute in Cambridge, Massachusetts. This alone is a lot more data.

All cells in the human body have the same genome, but use different parts of it. “It’s not enough to identify the genes for diseases, you also need to know where they are active.” The atlas, which is publicly available to researchers, can also be used to identify disease-causing cells.

The analysis of the mRNA is fundamental

Another Teichmann team examined the immune system of embryos in a fourth “Science” paper for the cell atlas and showed that immune cells develop in many organs, not just hematopoietic ones. “Examining the cells and tissues of the stages of human development helps us, among other things, to understand the rare diseases that often occur at birth and the origin of childhood cancers, which often develop during pregnancy,” explains Teichmann.

Prior to the ongoing work, around 100 individual studies that had analyzed the tissues of many people had already contributed to the cell atlas. A team led by Roland Eils of the Charité of Berlin had already drawn up a map of the pancreas in 2020: it genetically examined all the cells inside it, determined their exact location and clarified the connections between the individual cells.

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“We wanted to create a resource for all researchers interested in the pancreas,” Eils explained at the time. Norbert Hübner of the Max Delbrück Center for Molecular Medicine in Berlin did an initial sketch for the heart.

For the cell atlas, researchers analyze small working copies (mRNAs) of the genome, needed as instructions for making the desired substances in the cell. In the meantime, however, it is also possible to examine frozen tissue using cell nuclei alone. The cell atlas is not yet complete. “We actually wanted to have a first draft ready within five years,” said Teichmann. But the pandemic got in the way. One end is open.

“We don’t even know how many cell types humans have,” admits Teichmann, at least there are more of them than previously thought. “The body has over 50 tissues. Overall, we now have a rough map of 30 tissues and 50 million individual cells, “said Teichmann.” This is a great start. However, the brain is still gone. “Only small parts and in beings have been mapped. human there are about 100 brain regions.

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