A method that sheds light on the secrets of the brain: Optogenetics

Optogenetics, leading to the 2026 Nobel Prize in Medicine, allows for investigating brain function by controlling the activities of selected nerve cells with light. Prof. Muhsin Konuk stated that many processes, from memory to fear, from addiction to motor control, are examined with this method and said, “Optogenetics is currently a powerful laboratory research tool primarily used to unravel the underlying mechanisms of diseases.” Emphasizing that optogenetics research requires a strong infrastructure and the collaboration of different expertise areas, Prof. Konuk said, “Optogenetics is the perfect combination of genetics, neuroscience, and engineering disciplines.”

The awarding of the 2026 Nobel Prize in Physiology or Medicine to Karl Deisseroth, Peter Hegemann, and Georg Nagel for their discoveries in light-gated ion channels and optogenetics brought this method, which enables the control of nerve cells with light, to the forefront.

Prof. Muhsin Konuk, Advisor to the Rector of Üsküdar University and Faculty Member in Molecular Biology and Genetics (English), evaluated the scientific importance of optogenetics, its role in disease research, and the process of its transition to human application.

A discovery extending from an alga to brain research

Explaining that studies conducted on a light-seeking single-celled green alga were decisive in the development of optogenetics, Prof. Muhsin Konuk pointed out that basic science research can evolve into important applications in different fields over time.

Prof. Konuk stated, “The discovery of the protein that enables a single-celled alga, Chlamydomonas reinhardtii, to move towards light, transformed within approximately 20 years into a technology that allows scientists to switch specific brain cells on and off with light.”

Prof. Konuk, stating that the method combines genetics and light technologies, said, “In its simplest definition, optogenetics, is a method of controlling the activity of genetically selected cells using light. Here, ‘opto’ means light, while ‘genetics’ refers to the genetic modification of cells.”

Selected nerve cells can be intervened within milliseconds

Emphasizing that one of the most important features of optogenetics is its ability to focus on specific cell groups, Prof. Konuk stated that the method is particularly used to investigate the activities of nerve cells.

Prof. Konuk explained how the application works:

“For example, a researcher can make only certain dopamine-producing neurons light-sensitive among millions of brain cells. Then, by sending light into the brain through a very thin optical fiber, these cells can be activated or silenced within milliseconds.”

Stating that it is possible to investigate which cell group plays a role in which behavior through this method, Prof. Konuk expressed that providing both cell type selectivity and temporal precision is a significant gain for neuroscience.

It can be investigated which circuit plays a role in fear behavior

Explaining that observing the activation of a brain region during a specific behavior is different from testing the effect of that region on behavior, Prof. Konuk said that optogenetics contributes to the investigation of cause-and-effect relationships.

Prof. Konuk stated, “The functions of 86 billion nerve cells in the brain can be measured more clearly. For example, testing whether a specific neural circuit causes fear is possible thanks to this technology. Scientists can observe how fear behavior is affected by turning this circuit on and off with light.”

Noting that this approach offers researchers an important experimental opportunity to understand how neural circuits affect behavior, Prof. Konuk stated that the application areas of the method are becoming increasingly diverse.

Used in memory, sleep, and addiction research

Konuk stated that optogenetics is not a method focused on a single disease or brain function, but rather that the neural circuits underlying various behaviors and functions are examined with this technology.

Prof. Konuk said, “Optogenetics is used today in dozens of laboratories and has become one of the fundamental tools in examining the neural circuits that form processes such as memory, reward, motivation, sleep, fear, movement, addiction, and social behavior. Circuits related to Parkinson's, depression, addiction, pain, and other neurological/psychiatric disorders are also being investigated with this method.”

Stating that these studies aim to contribute not only to understanding disease mechanisms but also to the development of new treatment strategies, Prof. Konuk pointed out that research results and treatment applications in humans should be distinguished from each other.

Prof. Konuk stated that optogenetics makes it possible to control only a single selected cell type among billions of neurons in the brain with millisecond precision by combining genetic engineering and optical (light) technologies.

Research success does not mean routine treatment

Stating that developments in the field of optogenetics offer hope for the treatment of diseases, Prof. Konuk emphasized that the current status of the method, especially in brain diseases, should be accurately conveyed.

Prof. Konuk stated, “For diseases other than those of the eye, especially those originating from the brain, optogenetics is not yet an approved treatment, but an advanced research tool.”

Pointing out that findings obtained from animal experiments do not directly mean the same results will be achieved in humans, Prof. Konuk described the current role of the method with the words, “Optogenetics is currently a powerful laboratory research tool primarily used to unravel the underlying mechanisms of diseases.”

Human studies stand out in vision loss

Prof. Konuk stated that vision loss is one of the prominent areas in research on the application of optogenetics in humans, adding that work is being done especially on the inherited retinal disease called retinitis pigmentosa.

Explaining that the eye offers different possibilities compared to the brain in terms of light access, Prof. Konuk stated that results aiming at partial restoration of visual functions have been achieved in clinical studies in this field.

Prof. Konuk said, “Phase 1/2 human clinical trials are ongoing in this field, and striking results have been published.”

Neural circuits are being investigated in Parkinson's and epilepsy

Prof. Konuk reported that neural pathways related to motor control are being investigated using optogenetic methods in Parkinson's research, stating that how the stimulation or silencing of specific cell groups affects motor symptoms in experimental animals is being studied.

In epilepsy studies, Prof. Konuk stated that the focus is on suppressing excessive nerve cell activity, and that intervening in cellular activity through light-sensitive proteins is being evaluated for understanding seizure mechanisms and developing new approaches.
Prof. Konuk pointed out that in both fields, the distance between experimental findings and treatments that can be used in humans should be observed.

Joint work of genetics, neuroscience, and engineering is required

Emphasizing that optogenetics research requires a strong infrastructure and the collaboration of different expertise areas, Prof. Konuk said, “Optogenetics is the perfect combination of genetics, neuroscience, and engineering disciplines.”

Prof. Konuk stated that optogenetics studies in Turkey are carried out at the translational (applied) neuroscience level in a limited number of research centers and universities that are pioneers in genetics, engineering, and neuroscience, adding, “Especially with the awarding of the 2026 Nobel Prize in Medicine for optogenetic discoveries, interest in this field will further increase in research funds and university strategies in Turkey.”

Prof. Konuk stated that for studies in this field, molecular biology and virology laboratories, as well as laser and LED light sources, electrophysiological recording systems, advanced imaging capabilities, and experimental animal research infrastructure are needed.

Referring also to the facilities of Üsküdar University, Prof. Konuk stated, “In line with the motto 'Turkey's brain base,' our University possesses the majority of the infrastructure to conduct studies in this field.”