Peter Hegemann (born December 11, 1954) holds the Hertie Senior Research Chair for Neurosciences and is a professor of Experimental Biophysics at the Department of Biology, Faculty of Life Sciences, Humboldt University of Berlin, Germany. He is known for discovering channelrhodopsin, a type of ion channel that opens and closes when light is present, helping cells detect light. This discovery led to the development of optogenetics, a method that uses light to control the activity of specific brain cells. He has received many awards, including the Rumford Prize, the Shaw Prize in Life Science and Medicine, and the Albert Lasker Award for Basic Medical Research.

Early life and education

Hegemann was born in Münster in 1954 but grew up in Aachen. Many members of his family, including his parents, brother, and both grandfathers, are doctors. He attended a school focused on subjects like history and literature, which he did not like because he was not interested in classical studies. He enjoyed science classes and was first interested in exploring new lands, and later became interested in space. Later, he went to the University of Münster in 1975 to study chemistry. Two years later, he moved to the Ludwig Maximilian University of Munich to change his field of study to biochemistry.

After graduating in 1980, Hegemann earned his PhD at the Max Planck Institute of Biochemistry in the research group of Dieter Oesterhelt, who had recently become the director of the institute. He completed his PhD in 1984.

Career

After receiving a fellowship for his PhD thesis, Hegemann went to Syracuse University in 1985 as a postdoctoral researcher in Kenneth W. Foster's lab for one year. When he returned to Germany, he was given a five-year position as a principal investigator at the Max Planck Institute of Biochemistry.

In 1993, Hegemann became a professor in the Department of Biochemistry at the University of Regensburg. He later moved to Humboldt University of Berlin in 2004 and took a position as a professor of Experimental Biophysics. In 2015, he was given a Hertie Senior Research Chair for Neurosciences.

Research

Hegemann's research on light-controlled ion movement started during his PhD studies. He studied a protein called halorhodopsin, which is found in a type of ancient organism called haloarchaea. These organisms use light to move chloride ions against their natural flow. During his PhD, Hegemann studied halorhodopsin in a specific haloarchaea called Halobacterium salinarum. He found that yellow light activates this protein. When halorhodopsin is placed in neurons and exposed to light, chloride ions flow into the neurons, making the inside of the neurons more negative. This stops the neurons from sending electrical signals, which inactivates them.

In 1984, a scientist named Kenneth W. Foster from Syracuse University suggested that rhodopsins might also act as light sensors in a green alga called Chlamydomonas reinhardtii. This idea inspired Hegemann to work with Foster for a year as a postdoctoral researcher. After returning to Germany, Hegemann continued studying this rhodopsin. He tested another green alga and found that it had a quick electrical response to light, caused by ions moving through an ion channel. He proposed that the ion channel and the light-sensing rhodopsin were part of the same protein.

In 2002, Hegemann worked with Georg Nagel and Ernst Bamberg to identify the gene for this rhodopsin. They named it Channelrhodopsin-1. The next year, they discovered a second gene, named Channelrhodopsin-2. Both genes were copied from Chlamydomonas reinhardtii and placed into the cells of African clawed frog eggs. When blue light was used, electrical currents were detected in the frog eggs. When channelrhodopsins are placed in neurons and exposed to light, the ion channel opens, allowing positively charged ions like calcium and sodium to enter the neurons. This makes the inside of the neurons more positive, which activates them. This effect is the opposite of what happens with halorhodopsin.

These discoveries led to the development of a field called optogenetics. In 2005, Hegemann showed that channelrhodopsin could be used to control the movement of chicken embryos with light. Around the same time, a team of scientists, including Karl Deisseroth, Edward Boyden, Feng Zhang, Georg Nagel, and Ernst Bamberg, found that light could trigger electrical signals in neurons that had channelrhodopsin. Working with Deisseroth, Hegemann helped improve optogenetics by creating rhodopsin versions that respond faster, detect different light colors, and move different ions.

Using optogenetics, Hegemann and his team have shown that imbalances between excitatory and inhibitory neurons can lead to problems with behavior in mental disorders.