‘Powerhouse of the Cell’ may secretly help mammal’s eyes process light

(ORDO NEWS) — In order for you to read this article, the eyes must perform a rather complex task: light enters the cornea, passes through the pupil and lens to the retina, located behind, where light-sensitive cells, such as cones and rods, transmit information to the brain via electrical signals along the optic nerve. .

Now, according to the results of the study, a new amazing lens has been added to this process. In the cone receptors, the mitochondria – which, as you know, are the energy base of the cell – act like little “microlenses” to help deliver photons to the nerve cells. 

“We were surprised by this exciting phenomenon when it turned out that mitochondria have a dual purpose,” said Wei Li, senior author of the study, National Eye Institute neurologist, “their well-known metabolic role in energy production, as well as this optical effect.”

Mitochondria are amazing little organelles. They do the hard work in cells to generate most of the chemical energy needed for the cell to perform its functions. But if you remember what they look like in biology class, mitochondria don’t look like a structure that can effectively redirect light.

Powerhouse of the Cell May Secretly Help Mammals Eyes Process Light 2

This seemed especially strange to the researchers, since mitochondria are located in the light-sensitive outer segment of the cones in our retina. This means light can hit the mitochondria directly, potentially causing photons to scatter in strange directions or even absorb them, causing the light to stop reaching nerve cells altogether.

“These complex, lipid-rich organelles are also able to influence the passage of light into the outer segment,” write the researchers, led by National Eye Institute scientist John Ball.

“Here we show through live imaging and simulation that despite this risk of scattering or absorbing light, these densely packed mitochondria ‘focus’ light to penetrate the outer segment and that mitochondrial remodeling affects this concentration of light.”

The researchers used a thirteen-linear squirrel (Ictidomys tridecemlineatus) as a model organism. These animals are not nocturnal, so they have a lot of cones for color detection and not as many rods for seeing in the dark – at least compared to many other mammals. This allowed the researchers to view the isolated layer of cones containing living mitochondria.

Unfortunately, the squirrels had to be killed and their eyes opened; shortly after death, the retina was cut into pieces and placed on a microscope slide, removing layers until only light-sensitive cells (photoreceptors) remained.

This meant that researchers could shine their light on photoreceptors whose mitochondria were still alive and thus detect this interesting microlensing effect.

While mammalian cone cells should be fairly similar, we can’t yet say that this is exactly what happens in human cells as well – more research is needed for that. But it looks promising, and it also explains one unknown feature of the mammalian retina.

“The lens-like function of mitochondria may also explain a phenomenon known as the Stiles-Crawford effect,” says Ball.

The Stiles-Crawford effect is a property of cone receptors where light entering the center of the pupil causes a greater response in our cone cells than light entering closer to the edge.

Experimentally and with the help of computer models, the team found that the interaction of mitochondria with light corresponds to the Stiles-Crawford effect, which means that the mitochondria may be the cause.

“This ‘microlens-like’ feature of cone mitochondria delivers light with an angular dependence similar to the Stiles-Crawford effect, providing a simple explanation for this important visual phenomenon that improves resolution,” the team writes.

It seems that this energy center of the cell is moonlighting as a secret assistant to our vision.

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