Proteins shed light on the lens of the eye

The lens of the eye, the only transparent part of the human body, is made up of proteins that still hold many mysteries for medical scientists. In order to solve them, it’s necessary to eventually understand both the eye itself and eye diseases. Giuseppe Foffi’s team has been studying the physical properties of our human lens, and their findings have just been published.

The lens can be affected by cataract – a partial or total loss of its transparency. It’s made up of very dense proteins solution. These proteins are of differing sizes, and link up with each other according to the strength of their interaction, while ensuring the transparency of the eye. Giuseppe Foffi and his co-workers have further postulated that there is a weak interaction between the different types of proteins, and not only between those of the same group. They have now demonstrated this – both theoretically and experimentally – using simulations.

Age-related cataract is caused by mutations of proteins that are triggered by genetic factors, diabetes, or ultra-violet light . The lens, once formed, doesn’t re-generate itself: therefore, it’s essential to understand the properties of its proteins in order to determine how certain diseases affect it. The objective is to treat the disease early on, rather than trying to manage it when it’s already established, which is often unsatisfactory. Although cataract is easily operable in developed countries, it’s the main cause of blindness worldwide.

Cold cataract

The lens can also become opaque in response to a change in temperature. A lowering of temperature alters the properties of the proteins, which then no longer allow the light to pass through. This reversible phenomenon, called “cold cataract”, enables the understanding of the interactions between the molecules and the mechanisms of age-related cataract.

Giuseppe Foffi, Nicolas Dorsaz (former PhD student, Cambridge University), George Thurston (Rochester Institute of Technology), Peter Schurtenberger (University of Lund) and Anna Stradner (University of Fribourg) used proteins, extracted from bovine lenses and cooled, to perform their experiments and to prove the hypotheses on the interaction between the different types of proteins. To examine the opaque lenses, they used X-rays and neutrons. The results showed that the very weak value of the interaction confirms the simulations and is essential for the transparency of the eye. The team will now concentrate on performing the same experiments with the latest type of protein , which is the least known.

Beyond the perspectives for research and for the understanding of the eye and its pathologies, Giuseppe Foffi is enthusiastic: “There have been only two moments in my life where theory has predicted experimental results.” And even though the application of this research still seem far away, he reminds us that “before inventing the radio, it was necessary to discover the equations governing electro-magnetism”.


Author: Nicolas Guérin

Source: EPFL