Helmut Kettenmann in seiner Mikroskopie Ausstellung

Glia cell researcher, collector, science enabler

Glia cells are as indispensable as neurons. Yet they were long considered a mere “neural glue” – until Helmut Kettenmann came along. He initiated international glia cell research and helped it gain recognition. He was also part of the MDC’s founding generation and has continued to leave his mark on the institution over the last 30 years.

It is rare for scientists to devote their whole lives to one single subject. But that’s just what Prof. Helmut Kettenmann has done. In his early 20s, he wrote his diploma thesis at the University of Heidelberg on the characteristics of glia cells – a type of cell barely known at the time. Since then it has been the focus of his entire career as a neurobiologist. He founded a whole new field of research. Now he can look back upon three decades of work at the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC).

“Helmut Kettenmann belongs to the founding generation of our research institute and has left a lasting mark here,” says Prof. Thomas Sommer, interim Scientific Director of the MDC. “We owe him a great deal as a generator of ideas, as a passionate communicator of science and a co-founder of the Life Science Learning Lab – and as a glia cell researcher, of course.”

Glia cells are incredibly important in the brain. Yet even now they continue to be overshadowed by neurons. Numbering around 100 billion, they are about as plentiful in the human body as neurons, although they perform different tasks. “One of the key discoveries was that glia cells are not silent elements within the brain,” Kettenmann relates.

Microglia (pink) are a sort of garbage disposal for the brain. They quickly engulf small protein-coated latex balls and digest them.

There are three types of glia cells: oligodendrocytes, astrocytes, and microglia. While initially studying oligodendrocytes and astrocytes in the 1980s, Kettenmann’s lab discovered that these cells carry receptors for important messenger molecules (neurotransmitters). Then he became more and more interested in the third type: microglia. They are the brain’s immune cells. They protect this highly sensitive organ, which can barely regenerate itself, from infections such as meningitis. To do so, microglia can even take on amoeboid form and then move around the brain. In addition, Kettenmann’s team discovered that these watchdogs in the brain also have receptors on their surface for many important messenger molecules. They can “perceive” glutamate, as well as histamine and dopamine – the substances responsible for drive and reward. Since glia cells recognize all these neurotransmitters, they can precisely track the firing of neurons. They are therefore not simply passive filler in the brain, or a “neural glue,” as their discoverer Rudolf Virchow once described them. This was demonstrated by Kettenmann’s team, which was the first in the world to electrophysiologically characterize properties of glia cells in slices of the brain.

The start of a scientific community

From the beginning, Helmut Kettenmann has been central to creating broader scientific interest in glia cells and raising public awareness of their importance. That has been a major impulse for his involvement in the Life Science Learning Lab, the Long Night of the Sciences, and numerous other formats for engaging in popular science. And even though some scientists complain about having to write grant proposals because it subtracts from their own research time, he has always understood it as part of the job. The fruit of this labor puts a smile on his face today, as he talks about getting funding for the first time for a Priority Programme on glia from the German Research Foundation (DFG). “It was a milestone for the progress of glia research and the network we had created.” Since then, the community of glia specialists has successfully received grants for their research. And their results have consistently shown how significant glia cells are. They play a role in all neurodegenerative diseases, from dementia to multiple sclerosis.

Kettenmann therefore sees himself as a science enabler. He was committed to creating a network, a glia research community. That was part of the impetus for his becoming president of the first European Meeting on Glia Cells in Health and Disease, in 1994. Some 2,000 to 3,000 participants are now expected at the 2023 meeting in Berlin. “We booked the Estrel convention hotel,” Kettenmann proudly states.

A sense for the history of science

Retirement has not slowed Kettenmann’s efforts. He has remained active as a researcher and senior professor at Charité, and he is still closely connected with the MDC. Supported by lottery receipts, he is currently developing tours of the campus that highlight its rich history. He has long had a soft spot for the history of science. The shelves in his study are lined with countless leather- and cloth-bound volumes from past centuries. He has been collecting these treasures all his life – just like the classic cars he likes to drive around the campus. One especially rare work is Humboldt’s 1797 book on electrophysiology, “Versuche über die gereizte Muskel- und Nervenfaser nebst Vermutungen über den chemischen Prozess des Lebens in der Thier- und Pflanzenwelt” (Experiments on the excited muscle and nerve fiber with conjectures on the chemical process of life in the animal and vegetable world). Kettenmann is bequeathing to the MDC and Campus Berlin-Buch GmbH an impressive collection of microscopes built in Berlin and Brandenburg in the last 150 years. These research instruments, once made of shiny brass but now of synthetic materials, can be viewed at the campus or on a virtual tour.

Microscopy exhibition

Like most scientists, Helmut Kettenmann does not consider his profession a job but rather a passion and his life’s work. Accordingly, he does not intend to stop working completely. Since 2020, he has been leading a lab with five researchers at the Shenzhen Institute of Advanced Technology in China. His primary goal there is to continue studying the role played by microglia in brain tumors, dementia conditions, and psychiatric diseases. For as an important new insight shows, several risk genes for dementia disorders are responsible for proteins that microglia need. In the future, he intends to spend a quarter of his time in China but will maintain his residence in Berlin. That is not so easy during the pandemic. The People’s Republic of China currently requires a three-week quarantine in a state facility. But that will not stop Kettenmann.

Text: Susanne Donner


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